Oracle 10 g Good one
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This document provides an overview and summary of the Oracle Database SQL Reference manual. It includes information about the primary author and contributors, copyright details, and instructions that the document and programs are proprietary and protected. The document is not warranted to be error-free and restrictions apply to reproducing or transmitting its content.
![xv
8 Common SQL DDL Clauses
allocate_extent_clause ............................................................................................................................ 8-2
constraint .................................................................................................................................................. 8-4
deallocate_unused_clause .................................................................................................................... 8-26
file_specification ................................................................................................................................... 8-28
logging_clause ........................................................................................................................................ 8-36
parallel_clause ....................................................................................................................................... 8-39
physical_attributes_clause .................................................................................................................. 8-42
size_clause ............................................................................................................................................. 8-45
storage_clause ........................................................................................................................................ 8-46
9 SQL Queries and Subqueries
About Queries and Subqueries ............................................................................................................ 9-1
Creating Simple Queries ........................................................................................................................ 9-2
Hierarchical Queries ............................................................................................................................... 9-2
Hierarchical Query Examples .......................................................................................................... 9-5
The UNION [ALL], INTERSECT, MINUS Operators....................................................................... 9-7
Sorting Query Results ............................................................................................................................ 9-9
Joins ......................................................................................................................................................... 9-10
Join Conditions ............................................................................................................................... 9-10
Equijoins .......................................................................................................................................... 9-10
Self Joins .......................................................................................................................................... 9-11
Cartesian Products ......................................................................................................................... 9-11
Inner Joins ....................................................................................................................................... 9-11
Outer Joins ....................................................................................................................................... 9-11
Antijoins .......................................................................................................................................... 9-13
Semijoins .......................................................................................................................................... 9-13
Using Subqueries ................................................................................................................................. 9-13
Unnesting of Nested Subqueries ...................................................................................................... 9-14
Selecting from the DUAL Table ........................................................................................................ 9-15
Distributed Queries ............................................................................................................................. 9-15
10 SQL Statements: ALTER CLUSTER to ALTER JAVA
Types of SQL Statements .................................................................................................................... 10-1
Data Definition Language (DDL) Statements ............................................................................ 10-1
Data Manipulation Language (DML) Statements ..................................................................... 10-2
Transaction Control Statements ................................................................................................... 10-3
Session Control Statements ........................................................................................................... 10-3
System Control Statement ............................................................................................................. 10-3
Embedded SQL Statements .......................................................................................................... 10-3
How the SQL Statement Chapters are Organized ......................................................................... 10-3
ALTER CLUSTER ................................................................................................................................. 10-5
ALTER DATABASE ............................................................................................................................. 10-9
ALTER DIMENSION ........................................................................................................................ 10-45
ALTER DISKGROUP ........................................................................................................................ 10-48
ALTER FUNCTION ........................................................................................................................... 10-61](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-15-320.jpg)
![xviii
DROP FUNCTION ............................................................................................................................ 17-62
DROP INDEX....................................................................................................................................... 17-64
DROP INDEXTYPE ........................................................................................................................... 17-66
DROP JAVA ......................................................................................................................................... 17-67
DROP LIBRARY ................................................................................................................................. 17-68
DROP MATERIALIZED VIEW........................................................................................................ 17-69
DROP MATERIALIZED VIEW LOG ............................................................................................. 17-71
DROP OPERATOR ............................................................................................................................ 17-73
DROP OUTLINE ................................................................................................................................ 17-74
DROP PACKAGE ............................................................................................................................... 17-75
DROP PROCEDURE ......................................................................................................................... 17-77
DROP PROFILE .................................................................................................................................. 17-78
DROP RESTORE POINT ................................................................................................................. 17-79
DROP ROLE ........................................................................................................................................ 17-80
DROP ROLLBACK SEGMENT ...................................................................................................... 17-81
18
SQL Statements: DROP SEQUENCE to ROLLBACK
DROP SEQUENCE .............................................................................................................................. 18-2
DROP SYNONYM ............................................................................................................................... 18-3
DROP TABLE ........................................................................................................................................ 18-5
DROP TABLESPACE ........................................................................................................................... 18-9
DROP TRIGGER................................................................................................................................. 18-12
DROP TYPE ......................................................................................................................................... 18-13
DROP TYPE BODY ............................................................................................................................ 18-15
DROP USER ........................................................................................................................................ 18-16
DROP VIEW ........................................................................................................................................ 18-18
EXPLAIN PLAN .................................................................................................................................. 18-20
FLASHBACK DATABASE ................................................................................................................ 18-23
FLASHBACK TABLE ......................................................................................................................... 18-26
GRANT ................................................................................................................................................. 18-32
INSERT ................................................................................................................................................. 18-51
LOCK TABLE ...................................................................................................................................... 18-68
MERGE ................................................................................................................................................. 18-71
NOAUDIT ............................................................................................................................................ 18-76
PURGE .................................................................................................................................................. 18-80
RENAME .............................................................................................................................................. 18-82
REVOKE ............................................................................................................................................... 18-84
ROLLBACK ......................................................................................................................................... 18-92
19 SQL Statements: SAVEPOINT to UPDATE
SAVEPOINT .......................................................................................................................................... 19-2
SELECT ................................................................................................................................................... 19-4
SET CONSTRAINT[S] ...................................................................................................................... 19-48
SET ROLE ............................................................................................................................................ 19-50
SET TRANSACTION ........................................................................................................................ 19-52
TRUNCATE ......................................................................................................................................... 19-55](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-18-320.jpg)
![xxix
– STATS_KS_TEST
– STATS_MODE
– STATS_MW_TEST
– STATS_ONE_WAY_ANOVA
– T-test functions STATS_T_TEST_*
– STATS_WSR_TEST
The following SQL operators are new or enhanced in this release:
■ Equality and inequality operators (= and <>) can be used to compare nested tables
and varrays.
■ The hierarchical operator: CONNECT_BY_ROOT on page 4-5
■ The multiset operators: MULTISET EXCEPT on page 4-6, MULTISET INTERSECT
on page 4-7, and MULTISET UNION on page 4-8
The following pseudocolumns are new in this release:
■ The hierarchical pseudo columns: CONNECT_BY_ISLEAF Pseudocolumn on
page 3-2 and CONNECT_BY_ISCYCLE Pseudocolumn on page 3-1
■ The "Version Query Pseudocolumns" on page 3-5 let you extract information about
the rows returned by a version query.
■ The pseudocolumn ORA_ROWSCN Pseudocolumn on page 3-8 lets you obtain
the system change number of the most recent operation on a table.
The following conditions are new in this release:
■ The [NOT] IN conditions, formerly referred to as "membership condition", are now
documented as "IN conditions" to distinguish them from the new MEMBER
conditions (see IN Condition on page 7-21)
■ The "Floating-Point Conditions" (IS [NOT] NAN and IS [NOT] INFINITE) on
page 7-7
■ IS A SET Condition on page 7-11
■ IS ANY Condition on page 7-9
■ IS EMPTY Condition on page 7-11
■ IS PRESENT Condition on page 7-10
■ MEMBER Condition on page 7-12
■ REGEXP_LIKE Condition on page 7-17
■ SUBMULTISET Condition on page 7-13
The following miscellaneous features are added:
■ New locale-independent format elements have been added to the tables in
"Format Models" on page 2-54.
■ Oracle Database now performs implicit conversion between CLOB and NCLOB
data.
■ You can now specify a LOB column in the UPDATE OF clause when creating an
update DML trigger.](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-29-320.jpg)
![Datatypes
2-6 Oracle Database SQL Reference
Oracle Built-in Datatypes
The table that follows summarizes Oracle built-in datatypes. Please refer to the syntax
in the preceding sections for the syntactic elements. The codes listed for the datatypes
are used internally by Oracle Database. The datatype code of a column or object
attribute is returned by the DUMP function.
Table 2–1 Built-in Datatype Summary
Code Datatype Description
1 VARCHAR2(size [BYTE | CHAR]) Variable-length character string having maximum length size
bytes or characters. Maximum size is 4000 bytes or characters,
and minimum is 1 byte or 1 character. You must specify size for
VARCHAR2.
BYTE indicates that the column will have byte length semantics;
CHAR indicates that the column will have character semantics.
1 NVARCHAR2(size) Variable-length Unicode character string having maximum
length size characters. The number of bytes can be up to two
times size for AL16UTF16 encoding and three times size for
UTF8 encoding. Maximum size is determined by the national
character set definition, with an upper limit of 4000 bytes. You
must specify size for NVARCHAR2.
2 NUMBER[(precision [, scale]]) Number having precision p and scale s. The precision p can
range from 1 to 38. The scale s can range from -84 to 127.
8 LONG Character data of variable length up to 2 gigabytes, or 231
-1
bytes. Provided for backward compatibility.
12 DATE Valid date range from January 1, 4712 BC to December 31, 9999
AD. The default format is determined explicitly by the NLS_
DATE_FORMAT parameter or implicitly by the NLS_TERRITORY
parameter. The size is fixed at 7 bytes. This datatype contains the
datetime fields YEAR, MONTH, DAY, HOUR, MINUTE, and SECOND.
It does not have fractional seconds or a time zone.
21 BINARY_FLOAT 32-bit floating point number. This datatype requires 5 bytes,
including the length byte.
22 BINARY_DOUBLE 64-bit floating point number. This datatype requires 9 bytes,
including the length byte.
180 TIMESTAMP [(fractional_
seconds)]
Year, month, and day values of date, as well as hour, minute,
and second values of time, where fractional_seconds_
precision is the number of digits in the fractional part of the
SECOND datetime field. Accepted values of fractional_
seconds_precision are 0 to 9. The default is 6. The default
format is determined explicitly by the NLS_DATE_FORMAT
parameter or implicitly by the NLS_TERRITORY parameter. The
sizes varies from 7 to 11 bytes, depending on the precision. This
datatype contains the datetime fields YEAR, MONTH, DAY, HOUR,
MINUTE, and SECOND. It contains fractional seconds but does
not have a time zone.
181 TIMESTAMP [(fractional_
seconds)] WITH TIME ZONE
All values of TIMESTAMP as well as time zone displacement
value, where fractional_seconds_precision is the
number of digits in the fractional part of the SECOND datetime
field. Accepted values are 0 to 9. The default is 6. The default
format is determined explicitly by the NLS_DATE_FORMAT
parameter or implicitly by the NLS_TERRITORY parameter. The
size is fixed at 13 bytes. This datatype contains the datetime
fields YEAR, MONTH, DAY, HOUR, MINUTE, SECOND, TIMEZONE_
HOUR, and TIMEZONE_MINUTE. It has fractional seconds and an
explicit time zone.](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-40-320.jpg)
![Datatypes
Basic Elements of Oracle SQL 2-7
231 TIMESTAMP [(fractional_
seconds)] WITH LOCAL TIME ZONE
All values of TIMESTAMP WITH TIME ZONE, with the following
exceptions:
■ Data is normalized to the database time zone when it is
stored in the database.
■ When the data is retrieved, users see the data in the session
time zone.
The default format is determined explicitly by the NLS_DATE_
FORMAT parameter or implicitly by the NLS_TERRITORY
parameter. The sizes varies from 7 to 11 bytes, depending on the
precision.
182 INTERVAL YEAR [(year_
precision)] TO MONTH
Stores a period of time in years and months, where year_
precision is the number of digits in the YEAR datetime field.
Accepted values are 0 to 9. The default is 2. The size is fixed at 5
bytes.
183 INTERVAL DAY [(day_precision)]
TO SECOND [(fractional_
seconds)]
Stores a period of time in days, hours, minutes, and seconds,
where
■ day_precision is the maximum number of digits in the
DAY datetime field. Accepted values are 0 to 9. The default
is 2.
■ fractional_seconds_precision is the number of
digits in the fractional part of the SECOND field. Accepted
values are 0 to 9. The default is 6.
The size is fixed at 11 bytes.
23 RAW(size) Raw binary data of length size bytes. Maximum size is 2000
bytes. You must specify size for a RAW value.
24 LONG RAW Raw binary data of variable length up to 2 gigabytes.
69 ROWID Base 64 string representing the unique address of a row in its
table. This datatype is primarily for values returned by the
ROWID pseudocolumn.
208 UROWID [(size)] Base 64 string representing the logical address of a row of an
index-organized table. The optional size is the size of a column
of type UROWID. The maximum size and default is 4000 bytes.
96 CHAR [(size [BYTE | CHAR])] Fixed-length character data of length size bytes. Maximum
size is 2000 bytes or characters. Default and minimum size is
1 byte.
BYTE and CHAR have the same semantics as for VARCHAR2.
96 NCHAR[(size)] Fixed-length character data of length size characters. The
number of bytes can be up to two times size for AL16UTF16
encoding and three times size for UTF8 encoding. Maximum
size is determined by the national character set definition, with
an upper limit of 2000 bytes. Default and minimum size is 1
character.
112 CLOB A character large object containing single-byte or multibyte
characters. Both fixed-width and variable-width character sets
are supported, both using the database character set. Maximum
size is (4 gigabytes - 1) * (database block size).
Table 2–1 (Cont.) Built-in Datatype Summary
Code Datatype Description](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-41-320.jpg)
![Datatypes
Basic Elements of Oracle SQL 2-17
TO_DATE('
---------
01-MAY-05
Example This statement returns the Julian equivalent of January 1, 1997:
SELECT TO_CHAR(TO_DATE('01-01-1997', 'MM-DD-YYYY'),'J')
FROM DUAL;
TO_CHAR
--------
2450450
TIMESTAMP Datatype
The TIMESTAMP datatype is an extension of the DATE datatype. It stores the year,
month, and day of the DATE datatype, plus hour, minute, and second values. This
datatype is useful for storing precise time values. Specify the TIMESTAMP datatype as
follows:
TIMESTAMP [(fractional_seconds_precision)]
where fractional_seconds_precision optionally specifies the number of digits
Oracle stores in the fractional part of the SECOND datetime field. When you create a
column of this datatype, the value can be a number in the range 0 to 9. The default is 6.
TIMESTAMP WITH TIME ZONE Datatype
TIMESTAMP WITH TIME ZONE is a variant of TIMESTAMP that includes a time zone
offset in its value. The time zone offset is the difference (in hours and minutes)
between local time and UTC (Coordinated Universal Time—formerly Greenwich
Mean Time). This datatype is useful for collecting and evaluating date information
across geographic regions.
Specify the TIMESTAMP WITH TIME ZONE datatype as follows:
TIMESTAMP [(fractional_seconds_precision)] WITH TIME ZONE
where fractional_seconds_precision optionally specifies the number of digits
Oracle stores in the fractional part of the SECOND datetime field. When you create a
column of this datatype, the value can be a number in the range 0 to 9. The default is 6.
Oracle time zone data is derived from the public domain information available at
ftp://elsie.nci.nih.gov/pub/. Oracle time zone data may not reflect the most
recent data available at this site.
See Also: "Selecting from the DUAL Table" for a description of the
DUAL table
See Also: TO_TIMESTAMP on page 5-201 for information on
converting character data to TIMESTAMP data](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-51-320.jpg)
![Datatypes
2-18 Oracle Database SQL Reference
TIMESTAMP WITH LOCAL TIME ZONE Datatype
TIMESTAMP WITH LOCAL TIME ZONE is another variant of TIMESTAMP that includes a
time zone offset in its value. It differs from TIMESTAMP WITH TIME ZONE in that data
stored in the database is normalized to the database time zone, and the time zone
offset is not stored as part of the column data. When a user retrieves the data, Oracle
returns it in the user's local session time zone. The time zone offset is the difference (in
hours and minutes) between local time and UTC (Coordinated Universal
Time—formerly Greenwich Mean Time). This datatype is useful for displaying date
information in the time zone of the client system in a two-tier application.
Specify the TIMESTAMP WITH LOCAL TIME ZONE datatype as follows:
TIMESTAMP [(fractional_seconds_precision)] WITH LOCAL TIME ZONE
where fractional_seconds_precision optionally specifies the number of digits
Oracle stores in the fractional part of the SECOND datetime field. When you create a
column of this datatype, the value can be a number in the range 0 to 9. The default is 6.
Oracle time zone data is derived from the public domain information available at
ftp://elsie.nci.nih.gov/pub/. Oracle time zone data may not reflect the most
recent data available at this site.
INTERVAL YEAR TO MONTH Datatype
INTERVAL YEAR TO MONTH stores a period of time using the YEAR and MONTH
datetime fields. This datatype is useful for representing the difference between two
datetime values when only the year and month values are significant.
Specify INTERVAL YEAR TO MONTH as follows:
INTERVAL YEAR [(year_precision)] TO MONTH
where year_precision is the number of digits in the YEAR datetime field. The
default value of year_precision is 2.
You have a great deal of flexibility when specifying interval values as literals. Please
refer to "Interval Literals" on page 2-51 for detailed information on specify interval
See Also:
■ Oracle Database Globalization Support Guide for more information
on Oracle time zone data
■ "Support for Daylight Saving Times" on page 2-21 and Table 2–15,
" Datetime Format Elements" on page 2-59 for information on
daylight saving support
■ TO_TIMESTAMP_TZ on page 5-202 for information on converting
character data to TIMESTAMP WITH TIME ZONE data
■ ALTER SESSION on page 11-45 for information on the ERROR_
ON_OVERLAP_TIME session parameter
See Also:
■ Oracle Database Globalization Support Guide for more information
on Oracle time zone data
■ Oracle Database Application Developer's Guide - Fundamentals for
examples of using this datatype and CAST on page 5-24 for
information on converting character data to TIMESTAMP WITH
LOCAL TIME ZONE](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-52-320.jpg)
![Datatypes
Basic Elements of Oracle SQL 2-19
values as literals. Also see "Datetime and Interval Examples" on page 2-22 for an
example using intervals.
INTERVAL DAY TO SECOND Datatype
INTERVAL DAY TO SECOND stores a period of time in terms of days, hours, minutes,
and seconds. This datatype is useful for representing the precise difference between
two datetime values.
Specify this datatype as follows:
INTERVAL DAY [(day_precision)]
TO SECOND [(fractional_seconds_precision)]
where
■ day_precision is the number of digits in the DAY datetime field. Accepted
values are 0 to 9. The default is 2.
■ fractional_seconds_precision is the number of digits in the fractional part
of the SECOND datetime field. Accepted values are 0 to 9. The default is 6.
You have a great deal of flexibility when specifying interval values as literals. Please
refer to "Interval Literals" on page 2-51 for detailed information on specify interval
values as literals. Also see "Datetime and Interval Examples" on page 2-22 for an
example using intervals.
Datetime/Interval Arithmetic
You can perform a number of arithmetic operations on date (DATE), timestamp
(TIMESTAMP, TIMESTAMP WITH TIME ZONE, and TIMESTAMP WITH LOCAL TIME
ZONE) and interval (INTERVAL DAY TO SECOND and INTERVAL YEAR TO MONTH) data.
Oracle calculates the results based on the following rules:
■ You can use NUMBER constants in arithmetic operations on date and timestamp
values, but not interval values. Oracle internally converts timestamp values to
date values and interprets NUMBER constants in arithmetic datetime and interval
expressions as numbers of days. For example, SYSDATE + 1 is tomorrow. SYSDATE
- 7 is one week ago. SYSDATE + (10/1440) is ten minutes from now. Subtracting the
hire_date column of the sample table employees from SYSDATE returns the
number of days since each employee was hired. You cannot multiply or divide
date or timestamp values.
■ Oracle implicitly converts BINARY_FLOAT and BINARY_DOUBLE operands to
NUMBER.
■ Each DATE value contains a time component, and the result of many date
operations include a fraction. This fraction means a portion of one day. For
example, 1.5 days is 36 hours. These fractions are also returned by Oracle built-in
functions for common operations on DATE data. For example, the MONTHS_
BETWEEN function returns the number of months between two dates. The
fractional portion of the result represents that portion of a 31-day month.
■ If one operand is a DATE value or a numeric value (neither of which contains time
zone or fractional seconds components), then:
– Oracle implicitly converts the other operand to DATE data. (The exception is
multiplication of a numeric value times an interval, which returns an interval.)
– If the other operand has a time zone value, then Oracle uses the session time
zone in the returned value.](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-53-320.jpg)
![Datatypes
Basic Elements of Oracle SQL 2-31
■ Attributes, which are built-in types or other user-defined types. Attributes model
the structure of the real-world entity.
■ Methods, which are functions or procedures written in PL/SQL and stored in the
database, or written in a language like C or Java and stored externally. Methods
implement operations the application can perform on the real-world entity.
REF Datatypes
An object identifier (represented by the keyword OID) uniquely identifies an object
and enables you to reference the object from other objects or from relational tables. A
datatype category called REF represents such references. A REF datatype is a container
for an object identifier. REF values are pointers to objects.
When a REF value points to a nonexistent object, the REF is said to be "dangling". A
dangling REF is different from a null REF. To determine whether a REF is dangling or
not, use the condition IS [NOT] DANGLING. For example, given object view oc_
orders in the sample schema oe, the column customer_ref is of type REF to type
customer_typ, which has an attribute cust_email:
SELECT o.customer_ref.cust_email
FROM oc_orders o
WHERE o.customer_ref IS NOT DANGLING;
Varrays
An array is an ordered set of data elements. All elements of a given array are of the
same datatype. Each element has an index, which is a number corresponding to the
position of the element in the array.
The number of elements in an array is the size of the array. Oracle arrays are of
variable size, which is why they are called varrays. You must specify a maximum size
when you declare the varray.
When you declare a varray, it does not allocate space. It defines a type, which you can
use as:
■ The datatype of a column of a relational table
■ An object type attribute
■ A PL/SQL variable, parameter, or function return type
Oracle normally stores an array object either in line (that is, as part of the row data) or
out of line (in a LOB), depending on its size. However, if you specify separate storage
characteristics for a varray, then Oracle stores it out of line, regardless of its size. Please
refer to the varray_col_properties of CREATE TABLE on page 16-34 for more
information about varray storage.
Nested Tables
A nested table type models an unordered set of elements. The elements may be
built-in types or user-defined types. You can view a nested table as a single-column
table or, if the nested table is an object type, as a multicolumn table, with a column for
each attribute of the object type.
A nested table definition does not allocate space. It defines a type, which you can use
to declare:
■ The datatype of a column of a relational table
■ An object type attribute](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-65-320.jpg)
![Datatypes
2-34 Oracle Database SQL Reference
DBURIType DBURIType can be used to store DBURIRef values, which reference data
inside the database. Storing DBURIRef values lets you reference data stored inside or
outside the database and access the data consistently.
DBURIRef values use an XPath-like representation to reference data inside the
database. If you imagine the database as an XML tree, then you would see the tables,
rows, and columns as elements in the XML document. For example, the sample
human resources user hr would see the following XML tree:
<HR>
<EMPLOYEES>
<ROW>
<EMPLOYEE_ID>205</EMPLOYEE_ID>
<LAST_NAME>Higgins</LAST_NAME>
<SALARY>12000</SALARY>
.. <!-- other columns -->
</ROW>
... <!-- other rows -->
</EMPLOYEES>
<!-- other tables..-->
</HR>
<!-- other user schemas on which you have some privilege on..-->
The DBURIRef is an XPath expression over this virtual XML document. So to reference
the SALARY value in the EMPLOYEES table for the employee with employee number
205, we can write a DBURIRef as,
/HR/EMPLOYEES/ROW[EMPLOYEE_ID=205]/SALARY
Using this model, you can reference data stored in CLOB columns or other columns
and expose them as URLs to the external world.
URIFactory Package
Oracle also provides the URIFactory package, which can create and return instances
of the various subtypes of the URITypes. The package analyzes the URL string,
identifies the type of URL (HTTP, DBURI, and so on), and creates an instance of the
subtype. To create a DBURI instance, the URL must start with the prefix /oradb. For
example, URIFactory.getURI('/oradb/HR/EMPLOYEES') would create a
DBURIType instance and URIFactory.getUri('/sys/schema') would create an
XDBURIType instance.
Spatial Types
Oracle Spatial is designed to make spatial data management easier and more natural
to users of location-enabled applications, geographic information system (GIS)
applications, and geoimaging applications. After the spatial data is stored in an Oracle
See Also:
■ Oracle Database Application Developer's Guide - Object-Relational
Features for general information on object types and type
inheritance
■ Oracle XML Developer's Kit Programmer's Guide for more
information about these supplied types and their implementation
■ Oracle Streams Advanced Queuing User's Guide and Reference for
information about using XMLType with Oracle Advanced
Queuing](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-68-320.jpg)
![Datatype Comparison Rules
Basic Elements of Oracle SQL 2-39
■ ISO 8859/1 (International Standards Organization)
■ JEUC Japan Extended UNIX
Portions of the ASCII and EBCDIC character sets appear in Table 2–8 and Table 2–9.
Uppercase and lowercase letters are not equivalent. The numeric values for the
characters of a character set may not match the linguistic sequence for a particular
language.
Table 2–8 ASCII Character Set
Symbol Decimal value Symbol Decimal value
blank 32 ; 59
! 33 < 60
" 34 = 61
# 35 > 62
$ 36 ? 63
% 37 @ 64
& 38 A-Z 65-90
’ 39 [ 91
( 40 92
) 41 ] 93
* 42 ^ 94
+ 43 _ 95
, 44 ‘ 96
- 45 a-z 97-122
. 46 { 123
/ 47 | 124
0-9 48-57 } 125
: 58 ~ 126
Table 2–9 EBCDIC Character Set
Symbol Decimal value Symbol Decimal value
blank 64 % 108
¢ 74 _ 109
. 75 > 110
< 76 ? 111
( 77 : 122
+ 78 # 123
| 79 @ 124
& 80 ' 125
! 90 = 126
$ 91 " 127](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-73-320.jpg)
![Literals
2-46 Oracle Database SQL Reference
In the bottom branch of the syntax:
■ Q or q indicates that the alternative quoting mechanism will be used. This
mechanism allows a wide range of delimiters for the text string.
■ The outermost ' ' are two single quotation marks that precede and follow,
respectively, the opening and closing quote_delimiter.
■ c is any member of the user's character set. You can include quotation marks (") in
the text literal made up of c characters. You can also include the quote_
delimiter, as long as it is not immediately followed by a single quotation mark.
■ quote_delimiter is any single- or multibyte character except space, tab, and
return. The quote_delimiter can be a single quotation mark. However, if the
quote_delimiter appears in the text literal itself, ensure that it is not
immediately followed by a single quotation mark.
If the opening quote_delimiter is one of [, {, <, or (, then the closing quote_
delimiter must be the corresponding ], }, >, or ). In all other cases, the opening
and closing quote_delimiter must be the same character.
Text literals have properties of both the CHAR and VARCHAR2 datatypes:
■ Within expressions and conditions, Oracle treats text literals as though they have
the datatype CHAR by comparing them using blank-padded comparison semantics.
■ A text literal can have a maximum length of 4000 bytes.
Here are some valid text literals:
'Hello'
'ORACLE.dbs'
'Jackie''s raincoat'
'09-MAR-98'
N'nchar literal'
Here are some valid text literals using the alternative quoting mechanism:
q'!name LIKE '%DBMS_%%'!'
q'<'So,' she said, 'It's finished.'>'
q'{SELECT * FROM employees WHERE last_name = 'Smith';}'
nq'ï Ÿ1234 ï'
q'"name like '['"'
Numeric Literals
Use numeric literal notation to specify fixed and floating-point numbers.
Integer Literals
You must use the integer notation to specify an integer whenever integer appears in
expressions, conditions, SQL functions, and SQL statements described in other parts of
this reference.
The syntax of integer is as follows:
See Also: "Blank-Padded Comparison Semantics" on
page -HIDDEN](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-80-320.jpg)
![Literals
2-52 Oracle Database SQL Reference
Each type contains a leading field and may contain a trailing field. The leading field
defines the basic unit of date or time being measured. The trailing field defines the
smallest increment of the basic unit being considered. For example, a YEAR TO MONTH
interval considers an interval of years to the nearest month. A DAY TO MINUTE interval
considers an interval of days to the nearest minute.
If you have date data in numeric form, then you can use the NUMTOYMINTERVAL or
NUMTODSINTERVAL conversion function to convert the numeric data into interval
values.
Interval literals are used primarily with analytic functions.
INTERVAL YEAR TO MONTH
Specify YEAR TO MONTH interval literals using the following syntax:
interval_year_to_month::=
where
■ 'integer [-integer]' specifies integer values for the leading and optional
trailing field of the literal. If the leading field is YEAR and the trailing field is
MONTH, then the range of integer values for the month field is 0 to 11.
■ precision is the maximum number of digits in the leading field. The valid range
of the leading field precision is 0 to 9 and its default value is 2.
Restriction on the Leading Field If you specify a trailing field, it must be less
significant than the leading field. For example, INTERVAL '0-1' MONTH TO YEAR is not
valid.
The following INTERVAL YEAR TO MONTH literal indicates an interval of 123 years, 2
months:
INTERVAL '123-2' YEAR(3) TO MONTH
Examples of the other forms of the literal follow, including some abbreviated versions:
See Also: "Analytic Functions" on page 5-9, NUMTODSINTERVAL
on page 5-108, NUMTOYMINTERVAL on page 5-109, and Oracle
Database Data Warehousing Guide
Form of Interval Literal Interpretation
INTERVAL '123-2' YEAR(3) TO MONTH An interval of 123 years, 2 months. You must
specify the leading field precision if it is
greater than the default of 2 digits.
INTERVAL '123' YEAR(3) An interval of 123 years 0 months.
INTERVAL '300' MONTH(3) An interval of 300 months.
INTERVAL ’ integer
– integer
’
YEAR
MONTH
( precision )
TO
YEAR
MONTH](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-86-320.jpg)
![Literals
Basic Elements of Oracle SQL 2-53
You can add or subtract one INTERVAL YEAR TO MONTH literal to or from another to
yield another INTERVAL YEAR TO MONTH literal. For example:
INTERVAL '5-3' YEAR TO MONTH + INTERVAL'20' MONTH =
INTERVAL '6-11' YEAR TO MONTH
INTERVAL DAY TO SECOND
Specify DAY TO SECOND interval literals using the following syntax:
interval_day_to_second::=
where
■ integer specifies the number of days. If this value contains more digits than the
number specified by the leading precision, then Oracle returns an error.
■ time_expr specifies a time in the format HH[:MI[:SS[.n]]] or MI[:SS[.n]]
or SS[.n], where n specifies the fractional part of a second. If n contains more
digits than the number specified by fractional_seconds_precision, then n
is rounded to the number of digits specified by the fractional_seconds_
precision value. You can specify time_expr following an integer and a space
only if the leading field is DAY.
INTERVAL '4' YEAR Maps to INTERVAL '4-0' YEAR TO MONTH
and indicates 4 years.
INTERVAL '50' MONTH Maps to INTERVAL '4-2' YEAR TO MONTH
and indicates 50 months or 4 years 2 months.
INTERVAL '123' YEAR Returns an error, because the default precision
is 2, and '123' has 3 digits.
Form of Interval Literal Interpretation
INTERVAL ’
integer
integer time_expr
time_expr
’
DAY
HOUR
MINUTE
( leading_precision )
SECOND
( leading_precision
, fractional_seconds_precision
)
TO
DAY
HOUR
MINUTE
SECOND
( fractional_seconds_precision )](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-87-320.jpg)
![Format Models
2-60 Oracle Database SQL Reference
D Yes Day of week (1-7).
DAY Yes Name of day, padded with blanks to display width of the widest name of day in
the date language used for this element.
DD Yes Day of month (1-31).
DDD Yes Day of year (1-366).
DL Yes Returns a value in the long date format, which is an extension of Oracle
Database’s DATE format (the current value of the NLS_DATE_FORMAT
parameter). Makes the appearance of the date components (day name, month
number, and so forth) depend on the NLS_TERRITORY and NLS_LANGUAGE
parameters. For example, in the AMERICAN_AMERICA locale, this is equivalent to
specifying the format ’fmDay, Month dd, yyyy’. In the GERMAN_GERMANY
locale, it is equivalent to specifying the format ’fmDay, dd. Month yyyy’.
Restriction: You can specify this format only with the TS element, separated by
white space.
DS Yes Returns a value in the short date format. Makes the appearance of the date
components (day name, month number, and so forth) depend on the NLS_
TERRITORY and NLS_LANGUAGE parameters. For example, in the AMERICAN_
AMERICA locale, this is equivalent to specifying the format ’MM/DD/RRRR’. In the
ENGLISH_UNITED_KINGDOM locale, it is equivalent to specifying the format
’DD/MM/RRRR’.
Restriction: You can specify this format only with the TS element, separated by
white space.
DY Yes Abbreviated name of day.
E No Abbreviated era name (Japanese Imperial, ROC Official, and Thai Buddha
calendars).
EE No Full era name (Japanese Imperial, ROC Official, and Thai Buddha calendars).
FF [1..9] Yes Fractional seconds; no radix character is printed (use the X format element to add
the radix character). Use the numbers 1 to 9 after FF to specify the number of
digits in the fractional second portion of the datetime value returned. If you do
not specify a digit, then Oracle Database uses the precision specified for the
datetime datatype or the datatype’s default precision.
Examples: ’HH:MI:SS.FF’
SELECT TO_CHAR(SYSTIMESTAMP, ’SS.FF3’) from dual;
FM Yes Returns a value with no leading or trailing blanks.
See Also: Additional discussion on this format model modifier in the Oracle
Database SQL Reference
FX Yes Requires exact matching between the character data and the format model.
See Also: Additional discussion on this format model modifier in the Oracle
Database SQL Reference
HH Yes Hour of day (1-12).
HH12 No Hour of day (1-12).
HH24 Yes Hour of day (0-23).
IW No Week of year (1-52 or 1-53) based on the ISO standard.
IYY
IY
I
No Last 3, 2, or 1 digit(s) of ISO year.
Table 2–15 (Cont.) Datetime Format Elements
Element
Specify in TO_*
datetime
functions? Description](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-94-320.jpg)
![Multiset Operators
Operators 4-5
Hierarchical Query Operators
Two operators, PRIOR and CONNECT_BY_ROOT, are valid only in hierarchical queries.
PRIOR
In a hierarchical query, one expression in the CONNECT BY condition must be
qualified by the PRIOR operator. If the CONNECT BY condition is compound, then
only one condition requires the PRIOR operator, although you can have multiple
PRIOR conditions. PRIOR evaluates the immediately following expression for the
parent row of the current row in a hierarchical query.
PRIOR is most commonly used when comparing column values with the equality
operator. (The PRIOR keyword can be on either side of the operator.) PRIOR causes
Oracle to use the value of the parent row in the column. Operators other than the
equal sign (=) are theoretically possible in CONNECT BY clauses. However, the
conditions created by these other operators can result in an infinite loop through the
possible combinations. In this case Oracle detects the loop at run time and returns an
error. Please refer to "Hierarchical Queries" on page 9-2 for more information on this
operator, including examples.
CONNECT_BY_ROOT
CONNECT_BY_ROOT is a unary operator that is valid only in hierarchical queries.
When you qualify a column with this operator, Oracle returns the column value using
data from the root row. This operator extends the functionality of the CONNECT BY
[PRIOR] condition of hierarchical queries.
Restriction on CONNECT_BY_ROOT You cannot specify this operator in the START
WITH condition or the CONNECT BY condition.
Set Operators
Set operators combine the results of two component queries into a single result.
Queries containing set operators are called compound queries. Table 4–4 lists SQL set
operators. They are fully described, including examples and restrictions on these
operators, in "The UNION [ALL], INTERSECT, MINUS Operators" on page 9-7.
Multiset Operators
Multiset operators combine the results of two nested tables into a single nested table.
The examples related to multiset operators require that two nested tables be created
and loaded with data as follows:
See Also: "CONNECT_BY_ROOT Examples" on page 9-6
Table 4–4 Set Operators
Operator Returns
UNION All distinct rows selected by either query
UNION ALL All rows selected by either query, including all duplicates
INTERSECT All distinct rows selected by both queries
MINUS All distinct rows selected by the first query but not the second](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-157-320.jpg)
![DBTIMEZONE
5-50 Oracle Database SQL Reference
IGNORE NAV
UNIQUE DIMENSION
RULES UPSERT SEQUENTIAL ORDER
(
s[FOR prod IN ('Mouse Pad', 'Standard Mouse'), 2001] =
s[CV( ), 1999] + s[CV( ), 2000]
)
ORDER BY country, prod, year;
COUNTRY PROD YEAR S
---------- ----------------------------------- -------- ---------
France Mouse Pad 1998 2509.42
France Mouse Pad 1999 3678.69
France Mouse Pad 2000 3000.72
France Mouse Pad 2001 6679.41
France Standard Mouse 1998 2390.83
France Standard Mouse 1999 2280.45
France Standard Mouse 2000 1274.31
France Standard Mouse 2001 3554.76
Germany Mouse Pad 1998 5827.87
Germany Mouse Pad 1999 8346.44
Germany Mouse Pad 2000 7375.46
Germany Mouse Pad 2001 15721.9
Germany Standard Mouse 1998 7116.11
Germany Standard Mouse 1999 6263.14
Germany Standard Mouse 2000 2637.31
Germany Standard Mouse 2001 8900.45
16 rows selected.
The preceding example requires the view sales_view_ref. Refer to "The MODEL
clause: Examples" on page 19-35 to create this view.
DBTIMEZONE
Syntax
Purpose
DBTIMEZONE returns the value of the database time zone. The return type is a time
zone offset (a character type in the format '[+|-]TZH:TZM') or a time zone region
name, depending on how the user specified the database time zone value in the most
recent CREATE DATABASE or ALTER DATABASE statement.
Examples
The following example assumes that the database time zone is set to UTC time zone:
SELECT DBTIMEZONE FROM DUAL;
DBTIME
------
+00:00
DBTIMEZONE](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-212-320.jpg)
![INSERTXMLBEFORE
5-78 Oracle Database SQL Reference
INSERTXMLBEFORE
Syntax
Purpose
INSERTXMLBEFORE inserts a user-supplied value into the target XML before the node
indicated by the XPath expression. Compare this function with INSERTCHILDXML on
page 5-76.
■ XMLType_instance is an instance of XMLType.
■ The XPath_string is an Xpath expression indicating one or more nodes into
which one or more child nodes are to be inserted. You can specify an absolute
XPath_string with an initial slash or a relative XPath_string by omitting the
initial slash. If you omit the initial slash, the context of the relative path defaults to
the root node.
■ The value_expr is a fragment of XMLType that defines one or more nodes being
inserted and their position within the parent node. It must resolve to a string.
■ The optional namespace_string provides namespace information for the
XPath_string. This parameter must be of type VARCHAR2.
Examples
The following example is similar to that for INSERTCHILDXML on page 5-76, but it
adds a third /Owner node before the /Owner node added in the other example. The
output of the query has been formatted for readability.
UPDATE warehouses SET warehouse_spec =
INSERTXMLBEFORE(warehouse_spec,
'/Warehouse/Building/Owner[2]',
XMLType('<Owner>ThirdOwner</Owner>'))
WHERE warehouse_id = 3;
SELECT warehouse_name, EXTRACT(warehouse_spec,
'/Warehouse/Building/Owner') "Owners"
FROM warehouses
WHERE warehouse_id = 3;
Name Owners
------------ --------------------------------------------------------------------
New Jersey <Owner>Grandco</Owner>
<Owner>ThirdOwner</Owner>
<Owner>LesserCo</Owner>
See Also: Oracle XML DB Developer's Guide for more information
about this function
INSERTXMLBEFORE ( XMLType_instance , XPath_string , value_expr
, namespace_string
)](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-240-320.jpg)
![ITERATION_NUMBER
5-80 Oracle Database SQL Reference
SELECT INSTR('CORPORATE FLOOR','OR', -3, 2)
"Reversed Instring"
FROM DUAL;
Reversed Instring
-----------------
2
The next example assumes a double-byte database character set.
SELECT INSTRB('CORPORATE FLOOR','OR',5,2) "Instring in bytes"
FROM DUAL;
Instring in bytes
-----------------
27
ITERATION_NUMBER
Syntax
Purpose
The ITERATION_NUMBER function can be used only in the model_clause of the
SELECT statement and then only when ITERATE(number) is specified in the model_
rules_clause. It returns an integer representing the completed iteration through the
model rules. The ITERATION_NUMBER function returns 0 during the first iteration. For
each subsequent iteration, the ITERATION_NUMBER function returns the equivalent of
iteration_number plus one.
Examples
The following example assigns the sales of the Mouse Pad for the years 1998 and 1999
to the sales of the Mouse Pad for the years 2001 and 2002 respectively:
SELECT country, prod, year, s
FROM sales_view_ref
MODEL
PARTITION BY (country)
DIMENSION BY (prod, year)
MEASURES (sale s)
IGNORE NAV
UNIQUE DIMENSION
RULES UPSERT SEQUENTIAL ORDER ITERATE(2)
(
s['Mouse Pad', 2001 + ITERATION_NUMBER] =
s['Mouse Pad', 1998 + ITERATION_NUMBER]
)
ORDER BY country, prod, year;
COUNTRY PROD YEAR S
---------- ----------------------------------- -------- ---------
France Mouse Pad 1998 2509.42
France Mouse Pad 1999 3678.69
France Mouse Pad 2000 3000.72
See Also: model_clause on page 19-23 and "Model Expressions" on
page 6-11 for the syntax and semantics
ITERATION_NUMBER](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-242-320.jpg)
![LNNVL
5-88 Oracle Database SQL Reference
LNNVL
Syntax
Purpose
LNNVL provides a concise way to evaluate a condition when one or both operands of
the condition may be null. The function can be used only in the WHERE clause of a
query. It takes as an argument a condition and returns TRUE if the condition is FALSE
or UNKNOWN and FALSE if the condition is TRUE. LNNVL can be used anywhere a scalar
expression can appear, even in contexts where the IS [NOT] NULL, AND, or OR
conditions are not valid but would otherwise be required to account for potential
nulls. Oracle Database sometimes uses the LNNVL function internally in this way to
rewrite NOT IN conditions as NOT EXISTS conditions. In such cases, output from
EXPLAIN PLAN shows this operation in the plan table output. The condition can
evaluate any scalar values but cannot be a compound condition containing AND, OR, or
BETWEEN.
The table that follows shows what LNNVL returns given that a = 2 and b is null.
Examples
Suppose that you want to know the number of employees with commission rates of
less than 20%, including employees who do not receive commissions. The following
query returns only employees who actually receive a commission of less than 20%:
SELECT COUNT(*) FROM employees WHERE commission_pct < .2;
COUNT(*)
----------
11
To include the 72 employees who receive no commission at all, you could rewrite the
query using the LNNVL function as follows:
SELECT COUNT(*) FROM employees WHERE LNNVL(commission_pct >= .2);
COUNT(*)
----------
83
Condition Truth of Condition LNNVL Return Value
a = 1 FALSE TRUE
a = 2 TRUE FALSE
a IS NULL FALSE TRUE
b = 1 UNKNOWN TRUE
b IS NULL TRUE FALSE
a = b UNKNOWN TRUE
LNNVL ( condition )](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-250-320.jpg)
![PRESENTNNV
5-128 Oracle Database SQL Reference
100003 1 .09091 .91
100004 0 .90909 .73
100004 1 .09091 .91
100005 0 .27236 5.82
100005 1 .72764 .27
100006 0 1.00000 .00
100006 1 .00000 1.00
100007 0 .90909 .73
100007 1 .09091 .91
100008 0 .90909 .73
100008 1 .09091 .91
100009 0 .27236 5.82
100009 1 .72764 .27
100010 0 .80808 1.54
100010 1 .19192 .81
20 rows selected.
PRESENTNNV
Syntax
Purpose
The PRESENTNNV function can be used only in the model_clause of the SELECT
statement and then only on the right-hand side of a model rule. It returns expr1
when, prior to the execution of the model_clause, cell_reference exists and is
not null. Otherwise it returns expr2.
Examples
In the following example, if a row containing sales for the Mouse Pad for the year 2002
exists, and the sales value is not null, then the sales value remains unchanged. If the
row exists and the sales value is null, then the sales value is set to 10. If the row does
not exist, then the row is created with the sales value set to 10.
SELECT country, prod, year, s
FROM sales_view_ref
MODEL
PARTITION BY (country)
DIMENSION BY (prod, year)
MEASURES (sale s)
IGNORE NAV
UNIQUE DIMENSION
RULES UPSERT SEQUENTIAL ORDER
( s['Mouse Pad', 2002] =
PRESENTNNV(s['Mouse Pad', 2002], s['Mouse Pad', 2002], 10)
)
ORDER BY country, prod, year;
COUNTRY PROD YEAR S
---------- ----------------------------------- -------- ---------
France Mouse Pad 1998 2509.42
France Mouse Pad 1999 3678.69
See Also: model_clause on page 19-23 and "Model Expressions" on
page 6-11 for the syntax and semantics
PRESENTNNV ( cell_reference , expr1 , expr2 )](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-290-320.jpg)
![PRESENTV
Functions 5-129
France Mouse Pad 2000 3000.72
France Mouse Pad 2001 3269.09
France Mouse Pad 2002 10
France Standard Mouse 1998 2390.83
France Standard Mouse 1999 2280.45
France Standard Mouse 2000 1274.31
France Standard Mouse 2001 2164.54
Germany Mouse Pad 1998 5827.87
Germany Mouse Pad 1999 8346.44
Germany Mouse Pad 2000 7375.46
Germany Mouse Pad 2001 9535.08
Germany Mouse Pad 2002 10
Germany Standard Mouse 1998 7116.11
Germany Standard Mouse 1999 6263.14
Germany Standard Mouse 2000 2637.31
Germany Standard Mouse 2001 6456.13
18 rows selected.
The preceding example requires the view sales_view_ref. Please refer to
"Examples" on page 19-30 to create this view.
PRESENTV
Syntax
Purpose
The PRESENTV function can be used only within the model_clause of the SELECT
statement and then only on the right-hand side of a model rule. It returns expr1
when, prior to the execution of the model_clause, cell_reference exists.
Otherwise it returns expr2.
Examples
In the following example, if a row containing sales for the Mouse Pad for the year 2000
exists, then the sales value for the Mouse Pad for the year 2001 is set to the sales value
for the Mouse Pad for the year 2000. If the row does not exist, then a row is created
with the sales value for the Mouse Pad for year 20001 set to 0.
SELECT country, prod, year, s
FROM sales_view_ref
MODEL
PARTITION BY (country)
DIMENSION BY (prod, year)
MEASURES (sale s)
IGNORE NAV
UNIQUE DIMENSION
RULES UPSERT SEQUENTIAL ORDER
(
s['Mouse Pad', 2001] =
PRESENTV(s['Mouse Pad', 2000], s['Mouse Pad', 2000], 0)
)
See Also: model_clause on page 19-23 and "Model Expressions" on
page 6-11 for the syntax and semantics
PRESENTV ( cell_reference , expr1 , expr2 )](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-291-320.jpg)
![PREVIOUS
5-130 Oracle Database SQL Reference
ORDER BY country, prod, year;
COUNTRY PROD YEAR S
---------- ----------------------------------- -------- ---------
France Mouse Pad 1998 2509.42
France Mouse Pad 1999 3678.69
France Mouse Pad 2000 3000.72
France Mouse Pad 2001 3000.72
France Standard Mouse 1998 2390.83
France Standard Mouse 1999 2280.45
France Standard Mouse 2000 1274.31
France Standard Mouse 2001 2164.54
Germany Mouse Pad 1998 5827.87
Germany Mouse Pad 1999 8346.44
Germany Mouse Pad 2000 7375.46
Germany Mouse Pad 2001 7375.46
Germany Standard Mouse 1998 7116.11
Germany Standard Mouse 1999 6263.14
Germany Standard Mouse 2000 2637.31
Germany Standard Mouse 2001 6456.13
16 rows selected.
The preceding example requires the view sales_view_ref. Please refer to "The
MODEL clause: Examples" on page 19-35 to create this view.
PREVIOUS
Syntax
Purpose
The PREVIOUS function can be used only in the model_clause of the SELECT
statement and then only in the ITERATE ... [ UNTIL ] clause of the model_rules_
clause. It returns the value of cell_reference at the beginning of each iteration.
Examples
The following example repeats the rules, up to 1000 times, until the difference between
the values of cur_val at the beginning and at the end of an iteration is less than one:
SELECT dim_col, cur_val, num_of_iterations
FROM (SELECT 1 AS dim_col, 10 AS cur_val FROM dual)
MODEL
DIMENSION BY (dim_col)
MEASURES (cur_val, 0 num_of_iterations)
IGNORE NAV
UNIQUE DIMENSION
RULES ITERATE (1000) UNTIL (PREVIOUS(cur_val[1]) - cur_val[1] < 1)
(
cur_val[1] = cur_val[1]/2,
num_of_iterations[1] = num_of_iterations[1] + 1
);
See Also: model_clause on page 19-23 and "Model Expressions" on
page 6-11 for the syntax and semantics
PREVIOUS ( cell_reference )](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-292-320.jpg)
![REGEXP_INSTR
Functions 5-137
– 'i' specifies case-insensitive matching.
– 'c' specifies case-sensitive matching.
– 'n' allows the period (.), which is the match-any-character character, to match
the newline character. If you omit this parameter, the period does not match
the newline character.
– 'm' treats the source string as multiple lines. Oracle interprets ^ and $ as the
start and end, respectively, of any line anywhere in the source string, rather
than only at the start or end of the entire source string. If you omit this
parameter, Oracle treats the source string as a single line.
– ’x’ ignores whitespace characters. By default, whitespace characters match
themselves.
If you specify multiple contradictory values, Oracle uses the last value. For
example, if you specify 'ic', then Oracle uses case-sensitive matching. If you
specify a character other than those shown above, then Oracle returns an error.
If you omit match_parameter, then:
– The default case sensitivity is determined by the value of the NLS_SORT
parameter.
– A period (.) does not match the newline character.
– The source string is treated as a single line.
Examples
The following example examines the string, looking for occurrences of one or more
non-blank characters. Oracle begins searching at the first character in the string and
returns the starting position (default) of the sixth occurrence of one or more non-blank
characters.
SELECT
REGEXP_INSTR('500 Oracle Parkway, Redwood Shores, CA',
'[^ ]+', 1, 6) "REGEXP_INSTR"
FROM DUAL;
REGEXP_INSTR
------------
37
The following example examines the string, looking for occurrences of words
beginning with s, r, or p, regardless of case, followed by any six alphabetic characters.
Oracle begins searching at the third character in the string and returns the position in
the string of the character following the second occurrence of a seven-letter word
beginning with s, r, or p, regardless of case.
SELECT
REGEXP_INSTR('500 Oracle Parkway, Redwood Shores, CA',
'[s|r|p][[:alpha:]]{6}', 3, 2, 1, 'i') "REGEXP_INSTR"
FROM DUAL;
REGEXP_INSTR
See Also:
■ INSTR on page 5-79 and REGEXP_SUBSTR on page 5-140
■ REGEXP_REPLACE on page 5-138 and REGEXP_LIKE Condition
on page 7-17](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-299-320.jpg)
![REGEXP_REPLACE
Functions 5-139
■ match_parameter is a text literal that lets you change the default matching
behavior of the function. This argument affects only the matching process and has
no effect on replace_string. You can specify one or more of the following
values for match_parameter:
– 'i' specifies case-insensitive matching.
– 'c' specifies case-sensitive matching.
– 'n' allows the period (.), which is the match-any-character character, to match
the newline character. If you omit this parameter, the period does not match
the newline character.
– 'm' treats the source string as multiple lines. Oracle interprets ^ and $ as the
start and end, respectively, of any line anywhere in the source string, rather
than only at the start or end of the entire source string. If you omit this
parameter, Oracle treats the source string as a single line.
– ’x’ ignores whitespace characters. By default, whitespace characters match
themselves.
If you specify multiple contradictory values, Oracle uses the last value. For
example, if you specify 'ic', then Oracle uses case-sensitive matching. If you
specify a character other than those shown above, then Oracle returns an error.
If you omit match_parameter, then:
– The default case sensitivity is determined by the value of the NLS_SORT
parameter.
– A period (.) does not match the newline character.
– The source string is treated as a single line.
Examples
The following example examines phone_number, looking for the pattern
xxx.xxx.xxxx. Oracle reformats this pattern with (xxx) xxx-xxxx.
SELECT
REGEXP_REPLACE(phone_number,
'([[:digit:]]{3}).([[:digit:]]{3}).([[:digit:]]{4})',
'(1) 2-3') "REGEXP_REPLACE"
FROM employees;
REGEXP_REPLACE
--------------------------------------------------------------------------------
(515) 123-4567
(515) 123-4568
(515) 123-4569
(590) 423-4567
. . .
The following example examines country_name. Oracle puts a space after each
non-null character in the string.
SELECT
See Also:
■ REPLACE on page 5-148
■ REGEXP_INSTR on page 5-136, REGEXP_SUBSTR on page 5-140,
and REGEXP_LIKE Condition on page 7-17](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-301-320.jpg)
![REGEXP_SUBSTR
Functions 5-141
of the operators you can specify in pattern, please refer to Appendix C, "Oracle
Regular Expression Support".
■ position is a positive integer indicating the character of source_char where
Oracle should begin the search. The default is 1, meaning that Oracle begins the
search at the first character of source_char.
■ occurrence is a positive integer indicating which occurrence of pattern in
source_char Oracle should search for. The default is 1, meaning that Oracle
searches for the first occurrence of pattern.
■ match_parameter is a text literal that lets you change the default matching
behavior of the function. You can specify one or more of the following values for
match_parameter:
– 'i' specifies case-insensitive matching.
– 'c' specifies case-sensitive matching.
– 'n' allows the period (.), which is the match-any-character character, to match
the newline character. If you omit this parameter, the period does not match
the newline character.
– 'm' treats the source string as multiple lines. Oracle interprets ^ and $ as the
start and end, respectively, of any line anywhere in the source string, rather
than only at the start or end of the entire source string. If you omit this
parameter, Oracle treats the source string as a single line.
– ’x’ ignores whitespace characters. By default, whitespace characters match
themselves.
If you specify multiple contradictory values, Oracle uses the last value. For
example, if you specify 'ic', then Oracle uses case-sensitive matching. If you
specify a character other than those shown above, then Oracle returns an error.
If you omit match_parameter, then:
– The default case sensitivity is determined by the value of the NLS_SORT
parameter.
– A period (.) does not match the newline character.
– The source string is treated as a single line.
Examples
The following example examines the string, looking for the first substring bounded by
commas. Oracle Database searches for a comma followed by one or more occurrences
of non-comma characters followed by a comma. Oracle returns the substring,
including the leading and trailing commas.
SELECT
REGEXP_SUBSTR('500 Oracle Parkway, Redwood Shores, CA',
',[^,]+,') "REGEXPR_SUBSTR"
FROM DUAL;
REGEXPR_SUBSTR
-----------------
See Also:
■ SUBSTR on page 5-173 and REGEXP_INSTR on page 5-136
■ REGEXP_REPLACE on page 5-138, and REGEXP_LIKE Condition
on page 7-17](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-303-320.jpg)
![REGR_ (Linear Regression) Functions
5-142 Oracle Database SQL Reference
, Redwood Shores,
The following example examines the string, looking for http:// followed by a
substring of one or more alphanumeric characters and optionally, a period (.). Oracle
searches for a minimum of three and a maximum of four occurrences of this substring
between http:// and either a slash (/) or the end of the string.
SELECT
REGEXP_SUBSTR('http://www.oracle.com/products',
'http://([[:alnum:]]+.?){3,4}/?') "REGEXP_SUBSTR"
FROM DUAL;
REGEXP_SUBSTR
----------------------
http://www.oracle.com/
REGR_ (Linear Regression) Functions
The linear regression functions are:
■ REGR_SLOPE
■ REGR_INTERCEPT
■ REGR_COUNT
■ REGR_R2
■ REGR_AVGX
■ REGR_AVGY
■ REGR_SXX
■ REGR_SYY
■ REGR_SXY
Syntax
linear_regr::=
REGR_SLOPE
REGR_INTERCEPT
REGR_COUNT
REGR_R2
REGR_AVGX
REGR_AVGY
REGR_SXX
REGR_SYY
REGR_SXY
( expr1 , expr2 )
OVER ( analytic_clause )](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-304-320.jpg)
![SESSIONTIMEZONE
5-154 Oracle Database SQL Reference
SELECT SCN_TO_TIMESTAMP(ORA_ROWSCN) FROM employees
WHERE employee_id = 188;
SCN_TO_TIMESTAMP(ORA_ROWSCN)
---------------------------------------------------------------------------
28-AUG-03 01.58.01.000000000 PM
FLASHBACK TABLE employees TO TIMESTAMP
TO_TIMESTAMP('28-AUG-03 01.00.00.000000000 PM');
SELECT salary FROM employees WHERE employee_id = 188;
SALARY
----------
3800
SESSIONTIMEZONE
Syntax
Purpose
SESSIONTIMEZONE returns the time zone of the current session. The return type is a
time zone offset (a character type in the format '[+|]TZH:TZM') or a time zone
region name, depending on how the user specified the session time zone value in the
most recent ALTER SESSION statement.
Examples
The following example returns the time zone of the current session:
SELECT SESSIONTIMEZONE FROM DUAL;
SESSION
-------
-08:00
SET
Syntax
Purpose
SET converts a nested table into a set by eliminating duplicates. The function returns a
nested table whose elements are distinct from one another. The returned nested table is
of the same type as the input nested table.
The element types of the nested table must be comparable. Please refer to "Comparison
Conditions" on page 7-4 for information on the comparability of nonscalar types.
Note: You can set the default client session time zone using the ORA_
SDTZ environment variable. Please refer to Oracle Database
Globalization Support Guide for more information on this variable.
SESSIONTIMEZONE
SET ( nested_table )](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-316-320.jpg)
![SYS_EXTRACT_UTC
Functions 5-181
SYS_DBURIGEN
Syntax
Purpose
SYS_DBURIGen takes as its argument one or more columns or attributes, and
optionally a rowid, and generates a URL of datatype DBURIType to a particular
column or row object. You can then use the URL to retrieve an XML document from
the database.
All columns or attributes referenced must reside in the same table. They must perform
the function of a primary key. That is, they need not actually match the primary key of
the table, but they must reference a unique value. If you specify multiple columns,
then all but the final column identify the row in the database, and the last column
specified identifies the column within the row.
By default the URL points to a formatted XML document. If you want the URL to
point only to the text of the document, then specify the optional 'text()'.
If the table or view containing the columns or attributes does not have a schema
specified in the context of the query, then Oracle Database interprets the table or view
name as a public synonym.
Examples
The following example uses the SYS_DBURIGen function to generate a URL of
datatype DBURIType to the email column of the row in the sample table
hr.employees where the employee_id = 206:
SELECT SYS_DBURIGEN(employee_id, email)
FROM employees
WHERE employee_id = 206;
SYS_DBURIGEN(EMPLOYEE_ID,EMAIL)(URL, SPARE)
--------------------------------------------------------------------
DBURITYPE('/PUBLIC/EMPLOYEES/ROW[EMPLOYEE_ID=''206'']/EMAIL', NULL)
SYS_EXTRACT_UTC
Syntax
Note: In this XML context, the lowercase text is a keyword, not a
syntactic placeholder.
See Also: Oracle XML Developer's Kit Programmer's Guide for
information on the URIType datatype and XML documents in the
database
SYS_DBURIGEN (
column
attribute
rowid
,
, ’ text ( ) ’
)
SYS_EXTRACT_UTC ( datetime_with_timezone )](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-343-320.jpg)
![XMLCDATA
5-220 Oracle Database SQL Reference
Dept_list
---------------------------------------------------------
<Department>
<Employee>AD_ASST Whalen</Employee>
</Department>
<Department>
<Employee>MK_MAN Hartstein</Employee>
<Employee>MK_REP Fay</Employee>
</Department>
<Department>
<Employee>PU_MAN Raphaely</Employee>
<Employee>PU_CLERK Khoo</Employee>
<Employee>PU_CLERK Tobias</Employee>
<Employee>PU_CLERK Baida</Employee>
<Employee>PU_CLERK Colmenares</Employee>
<Employee>PU_CLERK Himuro</Employee>
</Department>
. . .
XMLCDATA
Syntax
Purpose
XMLCData generates a CDATA section by evaluating value_expr. The value_expr
must resolve to a string. The value returned by the function takes the following form:
<![CDATA[string]]>
If the resulting value is not a valid XML CDATA section, then the function returns an
error.
The following conditions apply to XMLCData:
■ The value_expr cannot contain the substring ]]>.
■ If value_expr evaluates to null, then the function returns null.
Examples
The following statement uses the DUAL table to illustrate the syntax of XMLCData:
SELECT XMLELEMENT("PurchaseOrder",
XMLAttributes(dummy as "pono"),
XMLCdata('<!DOCTYPE po_dom_group [
<!ELEMENT po_dom_group(student_name)*>
<!ELEMENT po_purch_name (#PCDATA)>
<!ATTLIST po_name po_no ID #REQUIRED>
<!ATTLIST po_name trust_1 IDREF #IMPLIED>
<!ATTLIST po_name trust_2 IDREF #IMPLIED>
]>')) "XMLCData" FROM DUAL;
See Also: Oracle XML DB Developer's Guide for more information on
this function
XMLCDATA ( value_expr )](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-382-320.jpg)
![XMLCOLATTVAL
Functions 5-221
XMLCData
----------------------------------------------------------
<PurchaseOrder pono="X"><![CDATA[
<!DOCTYPE po_dom_group [
<!ELEMENT po_dom_group(student_name)*>
<!ELEMENT po_purch_name (#PCDATA)>
<!ATTLIST po_name po_no ID #REQUIRED>
<!ATTLIST po_name trust_1 IDREF #IMPLIED>
<!ATTLIST po_name trust_2 IDREF #IMPLIED>
]>
]]>
</PurchaseOrder>
XMLCOLATTVAL
Syntax
Purpose
XMLColAttVal creates an XML fragment and then expands the resulting XML so that
each XML fragment has the name column with the attribute name. You can use the AS
c_alias clause to change the value of the name attribute to something other than the
column name.
You must specify a value for value_expr. If value_expr is null, then no element is
returned.
Restriction on XMLColAttVal You cannot specify an object type column for value_
expr.
Examples
The following example creates an Emp element for a subset of employees, with nested
employee_id, last_name, and salary elements as the contents of Emp. Each
nested element is named column and has a name attribute with the column name as
the attribute value:
SELECT XMLELEMENT("Emp",
XMLCOLATTVAL(e.employee_id, e.last_name, e.salary)) "Emp Element"
FROM employees e
WHERE employee_id = 204;
Emp Element
--------------------------------------------------------------------
<Emp>
<column name="EMPLOYEE_ID">204</column>
<column name="LAST_NAME">Baer</column>
<column name="SALARY">10000</column>
</Emp>
Please refer to the example for XMLFOREST on page 5-226 to compare the output of
these two functions.
XMLCOLATTVAL ( value_expr
AS c_alias
,
)](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-383-320.jpg)
![XMLSEQUENCE
Functions 5-229
XMLROOT
Syntax
Purpose
XMLROOT lets you create a new XML value by providing version and standalone
properties in the XML root information (prolog) of an existing XML value. If the
value_expr already has a prolog, then the database returns an error. If the input is
null, then the function returns null.
The value returned takes the following form:
<?xml version = "version" [ STANDALONE = "{yes | no}" ]?>
■ The first value_expr specifies the XML value for which you are providing
prolog information.
■ In the VERSION clause, value_expr must resolve to a string representing a valid
XML version. If you specify NO VALUE for VERSION, then the version defaults to
1.0.
■ If you omit the optional STANDALONE clause, or if you specify it with NO VALUE,
then the standalone property is absent from the value returned by the function.
Examples
The following statement uses the DUAL table to illustrate the syntax of XMLROOT:
SELECT XMLROOT ( XMLType('<poid>143598</poid>'), VERSION '1.0', STANDALONE YES)
AS "XMLROOT" FROM DUAL;
XMLROOT
--------------------------------------------------------------------------------
<?xml version="1.0" standalone="yes"?>
<poid>143598</poid>
XMLSEQUENCE
Syntax
Purpose
XMLSequence has two forms:
■ The first form takes as input an XMLType instance and returns a varray of the
top-level nodes in the XMLType. This form is effectively superseded by the
XMLROOT ( value_expr , VERSION
value_expr
NO VALUE
, STANDALONE
YES
NO
NO VALUE
)
XMLSEQUENCE (
XMLType_instance
sys_refcursor_instance
, fmt )](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-391-320.jpg)
![Model Expressions
6-12 Oracle Database SQL Reference
measure column previously defined in the model_clause. For additional
information, please refer to model_clause on page 19-23.
model_expression::=
When you specify a measure column in a model expression, any conditions and
expressions you specify must resolve to single values.
When you specify an aggregate function in a model expression, the argument to the
function is a measure column that has been previously defined in the model_clause.
An aggregate function can be used only on the right-hand side of a model rule.
Specifying an analytic function on the right-hand side of the model rule lets you
express complex calculations directly in the model_clause. The following
restrictions apply when using an analytic function in a model expression:
■ Analytic functions can be used only in an UPDATE rule.
■ You cannot specify an analytic function on the right-hand side of the model rule if
the left-hand side of the rule contains a FOR loop or an ORDER BY clause.
■ The arguments in the OVER clause of the analytic function cannot contain an
aggregate.
■ The arguments before the OVER clause of the analytic function cannot contain a
cell reference.
When expr is itself a model expression, it is referred to as a nested cell reference. The
following restrictions apply to nested cell references:
■ Only one level of nesting is allowed.
■ A nested cell reference must be a single-cell reference.
■ When AUTOMATIC ORDER is specified in the model_rules_clause, a nested cell
reference can be used on the left-hand side of a model rule only if the measure
used in the nested cell reference is never updated for any cell in the spreadsheet
clause.
See Also: "The MODEL clause: Examples" on page 19-35 for an
example of using an analytic function on the right-hand side of a
model rule
measure_column [
condition
expr
,
]
aggregate_function [
condition
expr
,
single_column_for_loop
,
multi_column_for_loop
]
analytic_function](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-412-320.jpg)
![Type Constructor Expressions
Expressions 6-13
The model expressions shown below are based on the model_clause of the
following SELECT statement:
SELECT country,prod,year,s
FROM sales_view_ref
MODEL
PARTITION BY (country)
DIMENSION BY (prod, year)
MEASURES (sale s)
IGNORE NAV
UNIQUE DIMENSION
RULES UPSERT SEQUENTIAL ORDER
(
s[prod='Mouse Pad', year=2000] =
s['Mouse Pad', 1998] + s['Mouse Pad', 1999],
s['Standard Mouse', 2001] = s['Standard Mouse', 2000]
)
ORDER BY country, prod, year;
The following model expression represents a single cell reference using symbolic
notation. It represents the sales of the Mouse Pad for the year 2000.
s[prod='Mouse Pad',year=2000]
The following model expression represents a multiple cell reference using positional
notation, using the CV function. It represents the sales of the current value of the
dimension column prod for the year 2001.
s[CV(prod), 2001]
The following model expression represents an aggregate function. It represents the
sum of sales of the Mouse Pad for the years between the current value of the
dimension column year less two and the current value of the dimension column
year less one.
SUM(s)['Mouse Pad',year BETWEEN CV()-2 AND CV()-1]
Type Constructor Expressions
A type constructor expression specifies a call to a constructor method. The argument
to the type constructor is any expression. Type constructors can be invoked anywhere
functions are invoked.
type_constructor_expression::=
The NEW keyword applies to constructors for object types but not for collection types.
It instructs Oracle to construct a new object by invoking an appropriate constructor.
The use of the NEW keyword is optional, but it is good practice to specify it.
If type_name is an object type, then the expressions must be an ordered list, where
the first argument is a value whose type matches the first attribute of the object type,
the second argument is a value whose type matches the second attribute of the object
See Also: CV on page 5-49 and model_clause on page 19-23
NEW schema .
type_name (
expr
,
)](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-413-320.jpg)
![Comparison Conditions
7-4 Oracle Database SQL Reference
Comparison Conditions
Comparison conditions compare one expression with another. The result of such a
comparison can be TRUE, FALSE, or NULL.
Large objects (LOBs) are not supported in comparison conditions. However, you can
use PL/SQL programs for comparisons on CLOB data.
When comparing numeric expressions, Oracle uses numeric precedence to determine
whether the condition compares NUMBER, BINARY_FLOAT, or BINARY_DOUBLE
values. Please refer to "Numeric Precedence" on page 2-13 for information on numeric
precedence.
Two objects of nonscalar type are comparable if they are of the same named type and
there is a one-to-one correspondence between their elements. In addition, nested tables
of user-defined object types, even if their elements are comparable, must have MAP
methods defined on them to be used in equality or IN conditions.
Table 7–2 lists comparison conditions.
=, !=, <, >, <=, >=, comparison
IS [NOT] NULL, LIKE, [NOT] BETWEEN,
[NOT] IN, EXISTS, IS OF type
comparison
NOT exponentiation, logical negation
AND conjunction
OR disjunction
See Also:
■ map_order_func_declaration on page 17-24 for more information on
MAP methods
■ Oracle Database PL/SQL User's Guide and Reference for the
requirements for comparing user-defined object types in PL/SQL
Table 7–2 Comparison Conditions
Type of
Condition Purpose Example
= Equality test. SELECT *
FROM employees
WHERE salary = 2500;
!=
^=
< >
¬=
Inequality test. Some forms of the inequality
condition may be unavailable on some platforms.
SELECT *
FROM employees
WHERE salary != 2500;
>
<
Greater-than and less-than tests. SELECT * FROM employees
WHERE salary > 2500;
SELECT * FROM employees
WHERE salary < 2500;
Table 7–1 (Cont.) SQL Condition Precedence
Type of Condition Purpose](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-420-320.jpg)
![Logical Conditions
Conditions 7-7
Floating-Point Conditions
The floating-point conditions let you determine whether an expression is infinite or is
the undefined result of an operation (that is, is not a number or NaN).
floating_point_conditions::=
In both forms of floating-point condition, expr must resolve to a numeric datatype or
to any datatype that can be implicitly converted to a numeric datatype. Table 7–3
describes the floating-point conditions.
Logical Conditions
A logical condition combines the results of two component conditions to produce a
single result based on them or to invert the result of a single condition. Table 7–4 lists
logical conditions.
Table 7–3 Floating-Point Conditions
Type of
Condition Operation Example
IS [NOT]
NAN
Returns TRUE if expr is the special
value NaN when NOT is not
specified. Returns TRUE if expr is
not the special value NaN when NOT
is specified.
SELECT COUNT(*) FROM employees
WHERE commission_pct IS NOT NAN;
IS [NOT]
INFINITE
Returns TRUE if expr is the special
value +INF or -INF when NOT is
not specified. Returns TRUE if expr
is neither +INF nor -INF when NOT
is specified.
SELECT last_name FROM employees
WHERE salary IS NOT INFINITE;
See Also:
■ "Floating-Point Numbers" on page 2-11 for more information on
the Oracle implementation of floating-point numbers
■ "Implicit Data Conversion" on page 2-41 for more information on
how Oracle converts floating-point datatypes
expr IS
NOT NAN
INFINITE](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-423-320.jpg)
![Model Conditions
Conditions 7-9
For example, the following query returns employees who have a 40% commission rate
or a salary greater than $20,000:
SELECT employee_id FROM employees
WHERE commission_pct = .4 OR salary > 20000;
Model Conditions
Model conditions can be used only in the MODEL clause of a SELECT statement.
IS ANY Condition
The IS ANY condition can be used only in the model_clause of a SELECT statement.
Use this condition to qualify all values of a dimension column, including NULL.
is_any_condition::=
The condition always returns a Boolean value of TRUE in order to qualify all values of
the column.
Example
The following example sets sales for each product for year 2000 to 0:
SELECT country, prod, year, s
FROM sales_view_ref
MODEL
PARTITION BY (country)
DIMENSION BY (prod, year)
MEASURES (sale s)
IGNORE NAV
UNIQUE DIMENSION
RULES UPSERT SEQUENTIAL ORDER
(
s[ANY, 2000] = 0
)
ORDER BY country, prod, year;
COUNTRY PROD YEAR S
---------- ----------------------------------- -------- ---------
France Mouse Pad 1998 2509.42
France Mouse Pad 1999 3678.69
France Mouse Pad 2000 0
France Mouse Pad 2001 3269.09
France Standard Mouse 1998 2390.83
France Standard Mouse 1999 2280.45
France Standard Mouse 2000 0
France Standard Mouse 2001 2164.54
Germany Mouse Pad 1998 5827.87
Germany Mouse Pad 1999 8346.44
Germany Mouse Pad 2000 0
Germany Mouse Pad 2001 9535.08
Germany Standard Mouse 1998 7116.11
See Also: model_clause on page 19-23 and "Model Expressions" on
page 6-11 for information
dimension_column IS
ANY](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-425-320.jpg)
![Model Conditions
7-10 Oracle Database SQL Reference
Germany Standard Mouse 1999 6263.14
Germany Standard Mouse 2000 0
Germany Standard Mouse 2001 6456.13
16 rows selected.
The preceding example requires the view sales_view_ref. Please refer to "The
MODEL clause: Examples" on page 19-35 to create this view.
IS PRESENT Condition
is_present_condition::=
The IS PRESENT condition can be used only in the model_clause of a SELECT
statement. Use this condition to test whether the cell referenced is present prior to the
execution of the model_clause.
The condition returns TRUE if the cell exists prior to the execution of the model_
clause and FALSE if it does not.
Example
In the following example, if sales of the Mouse Pad for year 1999 exist, then sales of the
Mouse Pad for year 2000 is set to sales of the Mouse Pad for year 1999. Otherwise,
sales of the Mouse Pad for year 2000 is set to 0.
SELECT country, prod, year, s
FROM sales_view_ref
MODEL
PARTITION BY (country)
DIMENSION BY (prod, year)
MEASURES (sale s)
IGNORE NAV
UNIQUE DIMENSION
RULES UPSERT SEQUENTIAL ORDER
(
s['Mouse Pad', 2000] =
CASE WHEN s['Mouse Pad', 1999] IS PRESENT
THEN s['Mouse Pad', 1999]
ELSE 0
END
)
ORDER BY country, prod, year;
COUNTRY PROD YEAR S
---------- ----------------------------------- -------- ---------
France Mouse Pad 1998 2509.42
France Mouse Pad 1999 3678.69
France Mouse Pad 2000 3678.69
France Mouse Pad 2001 3269.09
France Standard Mouse 1998 2390.83
France Standard Mouse 1999 2280.45
France Standard Mouse 2000 1274.31
France Standard Mouse 2001 2164.54
See Also: model_clause on page 19-23 and "Model Expressions" on
page 6-11 for information
cell_reference IS PRESENT](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-426-320.jpg)
![Multiset Conditions
Conditions 7-11
Germany Mouse Pad 1998 5827.87
Germany Mouse Pad 1999 8346.44
Germany Mouse Pad 2000 8346.44
Germany Mouse Pad 2001 9535.08
Germany Standard Mouse 1998 7116.11
Germany Standard Mouse 1999 6263.14
Germany Standard Mouse 2000 2637.31
Germany Standard Mouse 2001 6456.13
16 rows selected.
The preceding example requires the view sales_view_ref. Please refer to "The
MODEL clause: Examples" on page 19-35 to create this view.
Multiset Conditions
Multiset conditions test various aspects of nested tables.
IS A SET Condition
Use IS A SET conditions to test whether a specified nested table is composed of
unique elements. The condition returns NULL if the nested table is NULL. Otherwise, it
returns TRUE if the nested table is a set, even if it is a nested table of length zero, and
FALSE otherwise.
is_a_set_conditions::=
Example
The following example selects from the table customers_demo those rows in which
the cust_address_ntab nested table column contains unique elements:
SELECT customer_id, cust_address_ntab
FROM customers_demo
WHERE cust_address_ntab IS A SET;
CUSTOMER_ID CUST_ADDRESS_NTAB(STREET_ADDRESS, POSTAL_CODE, CITY, STATE_PROVINCE, COUNTRY_ID)
----------------------------------------------------------------------------------------------
101 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('514 W Superior St', '46901', 'Kokomo', 'IN', 'US'))
102 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('2515 Bloyd Ave', '46218', 'Indianapolis', 'IN', 'US'))
103 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('8768 N State Rd 37', '47404', 'Bloomington', 'IN', 'US'))
104 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('6445 Bay Harbor Ln', '46254', 'Indianapolis', 'IN', 'US'))
105 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('4019 W 3Rd St', '47404', 'Bloomington', 'IN', 'US'))
The preceding example requires the table customers_demo and a nested table
column containing data. Please refer to "Multiset Operators" on page 4-5 to create this
table and nested table column.
IS EMPTY Condition
Use the IS [NOT] EMPTY conditions to test whether a specified nested table is empty.
A nested table that consists of a single value, a NULL, is not considered an empty
nested table.
nested_table IS
NOT
A SET](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-427-320.jpg)
![Pattern-matching Conditions
Conditions 7-15
You can include the actual characters % or _ in the pattern by using the ESCAPE clause,
which identifies the escape character. If the escape character precedes the character %
or _ in the pattern, then Oracle interprets this character literally in the pattern rather
than as a special pattern-matching character. You can also search for the escape
character itself by repeating it. For example, if @ is the escape character, then you can
use @@ to search for @.
Table 7–8 describes the LIKE conditions.
To process the LIKE conditions, Oracle divides the pattern into subpatterns consisting
of one or two characters each. The two-character subpatterns begin with the escape
character and the other character is %, or _, or the escape character.
Let P1, P2, ..., Pn be these subpatterns. The like condition is true if there is a way to
partition the search value into substrings S1, S2, ..., Sn so that for all i between 1 and n:
■ If Pi is _, then Si is a single character.
■ If Pi is %, then Si is any string.
■ If Pi is two characters beginning with an escape character, then Si is the second
character of Pi.
■ Otherwise, Pi = Si.
With the LIKE conditions, you can compare a value to a pattern rather than to a
constant. The pattern must appear after the LIKE keyword. For example, you can issue
the following query to find the salaries of all employees with names beginning with R:
SELECT salary
FROM employees
WHERE last_name LIKE 'R%';
The following query uses the = operator, rather than the LIKE condition, to find the
salaries of all employees with the name 'R%':
SELECT salary
FROM employees
WHERE last_name = 'R%';
The following query finds the salaries of all employees with the name 'SM%'. Oracle
interprets 'SM%' as a text literal, rather than as a pattern, because it precedes the LIKE
keyword:
SELECT salary
FROM employees
WHERE 'SM%' LIKE last_name;
Table 7–8 LIKE Conditions
Type of
Condition Operation Example
x [NOT]
LIKE y
[ESCAPE
'z']
TRUE if x does [not] match the pattern
y. Within y, the character % matches any
string of zero or more characters except
null. The character _ matches any single
character. Any character can follow
ESCAPE except percent (%) and
underbar (_). A wildcard character is
treated as a literal if preceded by the
escape character.
SELECT last_name
FROM employees
WHERE last_name
LIKE '%A_B%' ESCAPE '';](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-431-320.jpg)
![Range Conditions
7-18 Oracle Database SQL Reference
– A period (.) does not match the newline character.
– The source string is treated as a single line.
Examples
The following query returns the first and last names for those employees with a first
name of Steven or Stephen (where first_name begins with Ste and ends with en
and in between is either v or ph):
SELECT first_name, last_name
FROM employees
WHERE REGEXP_LIKE (first_name, '^Ste(v|ph)en$');
FIRST_NAME LAST_NAME
-------------------- -------------------------
Steven King
Steven Markle
Stephen Stiles
The following query returns the last name for those employees with a double vowel in
their last name (where last_name contains two adjacent occurrences of either a, e, i,
o, or u, regardless of case):
SELECT last_name
FROM employees
WHERE REGEXP_LIKE (last_name, '([aeiou])1', 'i');
LAST_NAME
-------------------------
De Haan
Greenberg
Khoo
Gee
Greene
Lee
Bloom
Feeney
Range Conditions
A range condition tests for inclusion in a range.
range_conditions::=
Table 7–9 describes the range conditions.
See Also:
■ "LIKE Condition" on page 7-14
■ REGEXP_INSTR on page 5-136, REGEXP_REPLACE on
page 5-138, and REGEXP_SUBSTR on page 5-140 for functions
that provide regular expression support
expr
NOT
BETWEEN expr AND expr](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-434-320.jpg)
![XML Conditions
Conditions 7-19
Null Conditions
A NULL condition tests for nulls. This is the only condition that you should use to test
for nulls.
null_conditions::=
Table 7–10 lists the null conditions.
XML Conditions
XML conditions determines whether a specified XML resource can be found in a
specified path.
EQUALS_PATH Condition
The EQUALS_PATH condition determines whether a resource in the Oracle XML
database can be found in the database at a specified path.
Use this condition in queries to RESOURCE_VIEW and PATH_VIEW. These public views
provide a mechanism for SQL access to data stored in the XML database repository.
RESOURCE_VIEW contains one row for each resource in the repository, and PATH_
VIEW contains one row for each unique path in the repository.
equals_path_condition::=
This condition applies only to the path as specified. It is similar to but more restrictive
than UNDER_PATH.
The optional correlation_integer argument correlates the EQUALS_PATH
condition with its ancillary functions DEPTH and PATH.
Table 7–9 Range Conditions
Type of
Condition Operation Example
[NOT]
BETWEEN x
AND y
[Not] greater than or equal to x
and less than or equal to y.
SELECT * FROM employees
WHERE salary
BETWEEN 2000 AND 3000;
Table 7–10 Null Conditions
Type of
Condition Operation Example
IS [NOT]
NULL
Tests for nulls.
See Also: "Nulls" on page 2-68
SELECT last_name
FROM employees
WHERE commission_pct
IS NULL;
expr IS
NOT
NULL
EQUALS_PATH ( column , path_string
, correlation_integer
)](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-435-320.jpg)
![IS OF type Condition
Conditions 7-23
Because the third condition compares department_id with a null, it results in an
UNKNOWN, so the entire expression results in FALSE (for rows with department_id
equal to 10 or 20). This behavior can easily be overlooked, especially when the NOT IN
operator references a subquery.
Moreover, if a NOT IN condition references a subquery that returns no rows at all, then
all rows will be returned, as shown in the following example:
SELECT 'True' FROM employees
WHERE department_id NOT IN (SELECT 0 FROM DUAL WHERE 1=2);
Restriction on LEVEL in WHERE Clauses In a [NOT] IN condition in a WHERE clause,
if the right-hand side of the condition is a subquery, you cannot use LEVEL on the
left-hand side of the condition. However, you can specify LEVEL in a subquery of the
FROM clause to achieve the same result. For example, the following statement is not
valid:
SELECT employee_id, last_name FROM employees
WHERE (employee_id, LEVEL)
IN (SELECT employee_id, 2 FROM employees)
START WITH employee_id = 2
CONNECT BY PRIOR employee_id = manager_id;
But the following statement is valid because it encapsulates the query containing the
LEVEL information in the FROM clause:
SELECT v.employee_id, v.last_name, v.lev
FROM
(SELECT employee_id, last_name, LEVEL lev
FROM employees v
START WITH employee_id = 100
CONNECT BY PRIOR employee_id = manager_id) v
WHERE (v.employee_id, v.lev) IN
(SELECT employee_id, 2 FROM employees);
IS OF type Condition
Use the IS OF type condition to test object instances based on their specific type
information.
is_of_type_conditions::=
You must have EXECUTE privilege on all types referenced by type, and all types
must belong to the same type family.
This condition evaluates to null if expr is null. If expr is not null, then the condition
evaluates to true (or false if you specify the NOT keyword) under either of these
circumstances:
■ The most specific type of expr is the subtype of one of the types specified in the
type list and you have not specified ONLY for the type, or
■ The most specific type of expr is explicitly specified in the type list.
The expr frequently takes the form of the VALUE function with a correlation variable.
expr IS
NOT
OF
TYPE
(
ONLY schema .
type
,
)](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-439-320.jpg)
![constraint
8-8 Oracle Database SQL Reference
Semantics
This section describes the semantics of constraint. For additional information, refer
to the SQL statement in which you define or redefine a constraint for a table or view.
Oracle Database does not support constraints on columns or attributes whose type is a
user-defined object, nested table, VARRAY, REF, or LOB, with two exceptions:
■ NOT NULL constraints are supported for a column or attribute whose type is
user-defined object, VARRAY, REF, or LOB.
■ NOT NULL, foreign key, and REF constraints are supported on a column of type
REF.
CONSTRAINT constraint_name Specify a name for the constraint. If you omit this
identifier, then Oracle Database generates a name with the form SYS_Cn. Oracle stores
the name and the definition of the integrity constraint in the USER_, ALL_, and DBA_
CONSTRAINTS data dictionary views (in the CONSTRAINT_NAME and SEARCH_
CONDITION columns, respectively).
NOT NULL Constraints
A NOT NULL constraint prohibits a column from containing nulls. The NULL keyword
by itself does not actually define an integrity constraint, but you can specify it to
explicitly permit a column to contain nulls. You must define NOT NULL and NULL
using inline specification. If you specify neither NOT NULL nor NULL, then the default
is NULL.
NOT NULL constraints are the only constraints you can specify inline on XMLType and
VARRAY columns.
To satisfy a NOT NULL constraint, every row in the table must contain a value for the
column.
Restrictions on NOT NULL Constraints NOT NULL constraints are subject to the
following restrictions:
■ You cannot specify NULL or NOT NULL in a view constraint.
■ You cannot specify NULL or NOT NULL for an attribute of an object. Instead, use a
CHECK constraint with the IS [NOT] NULL condition.
Unique Constraints
A unique constraint designates a column as a unique key. A composite unique key
designates a combination of columns as the unique key. When you define a unique
constraint inline, you need only the UNIQUE keyword. When you define a unique
See Also: Oracle Database Reference for information on the data
dictionary views
Note: Oracle Database does not index table rows in which all key
columns are null except in the case of bitmap indexes. Therefore, if
you want an index on all rows of a table, then you must either specify
NOT NULL constraints for at least one of the index key columns or
create a bitmap index.
See Also: "Attribute-Level Constraints Example" on page 8-24 and
"NOT NULL Example" on page 8-20](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-448-320.jpg)
![constraint
8-14 Oracle Database SQL Reference
■ Oracle implicitly adds a scope constraint when you add a referential integrity
constraint to an existing unscoped REF column. Therefore, all the restrictions that
apply for scope constraints also apply in this case.
■ You cannot specify a column after the object name in the references_clause.
Specifying Constraint State
As part of constraint definition, you can specify how and when Oracle should enforce
the constraint.
constraint_state You can use the constraint_state with both inline and
out-of-line specification. You can specify the clauses of constraint_state in any
order, but you can specify each clause only once.
DEFERRABLE Clause The DEFERRABLE and NOT DEFERRABLE parameters indicate
whether or not, in subsequent transactions, constraint checking can be deferred until
the end of the transaction using the SET CONSTRAINT(S) statement. If you omit this
clause, then the default is NOT DEFERRABLE.
■ Specify NOT DEFERRABLE to indicate that in subsequent transactions you cannot
use the SET CONSTRAINT[S] clause to defer checking of this constraint until the
transaction is committed. The checking of a NOT DEFERRABLE constraint can
never be deferred to the end of the transaction.
If you declare a new constraint NOT DEFERRABLE, then it must be valid at the time
the CREATE TABLE or ALTER TABLE statement is committed or the statement will
fail.
■ Specify DEFERRABLE to indicate that in subsequent transactions you can use the
SET CONSTRAINT[S] clause to defer checking of this constraint until after the
transaction is committed. This setting in effect lets you disable the constraint
temporarily while making changes to the database that might violate the
constraint until all the changes are complete.
You cannot alter the deferrability of a constraint. That is, whether you specify either of
these parameters, or make the constraint NOT DEFERRABLE implicitly by specifying
neither of them, you cannot specify this clause in an ALTER TABLE statement. You
must drop the constraint and re-create it.
Restriction on [NOT] DEFERRABLE You cannot specify either of these parameters
for a view constraint.
INITIALLY Clause The INITIALLY clause establishes the default checking behavior
for constraints that are DEFERRABLE. The INITIALLY setting can be overridden by a
SET CONSTRAINT(S) statement in a subsequent transaction.
■ Specify INITIALLY IMMEDIATE to indicate that Oracle should check this
constraint at the end of each subsequent SQL statement. If you do not specify
INITIALLY at all, then the default is INITIALLY IMMEDIATE.
See Also:
■ SET CONSTRAINT[S] on page 19-48 for information on setting
constraint checking for a transaction
■ Oracle Database Administrator's Guide and Oracle Database Concepts
for more information about deferred constraints
■ "DEFERRABLE Constraint Examples" on page 8-25](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-454-320.jpg)
![logging_clause
Common SQL DDL Clauses 8-37
statement (and in subsequent ALTER ... ADD PARTITION statements), unless you
specify the logging attribute in the PARTITION description.
If the object for which you are specifying the logging attributes resides in a database or
tablespace in force logging mode, then Oracle Database ignores any NOLOGGING
setting until the database or tablespace is taken out of force logging mode.
If the database is run in archivelog mode, then media recovery from a backup made
before the LOGGING operation re-creates the object. However, media recovery from a
backup made before the NOLOGGING operation does not re-create the object.
The size of a redo log generated for an operation in NOLOGGING mode is significantly
smaller than the log generated in LOGGING mode.
In NOLOGGING mode, data is modified with minimal logging (to mark new extents
INVALID and to record dictionary changes). When applied during media recovery, the
extent invalidation records mark a range of blocks as logically corrupt, because the
redo data is not fully logged. Therefore, if you cannot afford to lose the database
object, then you should take a backup after the NOLOGGING operation.
NOLOGGING is supported in only a subset of the locations that support LOGGING. Only
the following operations support the NOLOGGING mode:
DML:
■ Direct-path INSERT (serial or parallel) resulting either from an INSERT or a
MERGE statement. NOLOGGING is not applicable to any UPDATE operations
resulting from the MERGE statement.
■ Direct Loader (SQL*Loader)
DDL:
■ CREATE TABLE ... AS SELECT
■ CREATE TABLE ... LOB_storage_clause ... LOB_parameters ... NOCACHE |
CACHE READS
■ ALTER TABLE ... LOB_storage_clause ... LOB_parameters ... NOCACHE |
CACHE READS (to specify logging of newly created LOB columns)
■ ALTER TABLE ... modify_LOB_storage_clause ... modify_LOB_parameters
... NOCACHE | CACHE READS (to change logging of existing LOB columns)
■ ALTER TABLE ... MOVE
■ ALTER TABLE ... (all partition operations that involve data movement)
– ALTER TABLE ... ADD PARTITION (hash partition only)
– ALTER TABLE ... MERGE PARTITIONS
– ALTER TABLE ... SPLIT PARTITION
– ALTER TABLE ... MOVE PARTITION
– ALTER TABLE ... MODIFY PARTITION ... ADD SUBPARTITION
– ALTER TABLE ... MODIFY PARTITION ... COALESCE SUBPARTITION
■ CREATE INDEX
■ ALTER INDEX ... REBUILD
■ ALTER INDEX ... REBUILD [SUB]PARTITION
■ ALTER INDEX ... SPLIT PARTITION](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-477-320.jpg)
![SQL Queries and Subqueries 9-1
9
SQL Queries and Subqueries
This chapter describes SQL queries and subqueries.
This chapter contains these sections:
■ About Queries and Subqueries
■ Creating Simple Queries
■ Hierarchical Queries
■ The UNION [ALL], INTERSECT, MINUS Operators
■ Sorting Query Results
■ Joins
■ Using Subqueries
■ Unnesting of Nested Subqueries
■ Selecting from the DUAL Table
■ Distributed Queries
About Queries and Subqueries
A query is an operation that retrieves data from one or more tables or views. In this
reference, a top-level SELECT statement is called a query, and a query nested within
another SQL statement is called a subquery.
This section describes some types of queries and subqueries and how to use them. The
top level of the syntax is shown in this chapter. Please refer to SELECT on page 19-4
for the full syntax of all the clauses and the semantics of this statement.
select::=
subquery
for_update_clause
;](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-493-320.jpg)
![Hierarchical Queries
SQL Queries and Subqueries 9-3
hierarchical_query_clause::=
START WITH specifies the root row(s) of the hierarchy.
CONNECT BY specifies the relationship between parent rows and child rows of the
hierarchy.
■ The NOCYCLE parameter instructs Oracle Database to return rows from a query
even if a CONNECT BY LOOP exists in the data. Use this parameter along with the
CONNECT_BY_ISCYCLE pseudocolumn to see which rows contain the loop. Please
refer to CONNECT_BY_ISCYCLE Pseudocolumn on page 3-1 for more
information.
■ In a hierarchical query, one expression in condition must be qualified with the
PRIOR operator to refer to the parent row. For example,
... PRIOR expr = expr
or
... expr = PRIOR expr
If the CONNECT BY condition is compound, then only one condition requires the
PRIOR operator, although you can have multiple PRIOR conditions. For example:
CONNECT BY last_name != 'King' AND PRIOR employee_id = manager_id ...
CONNECT BY PRIOR employee_id = manager_id and
PRIOR account_mgr_id = customer_id ...
PRIOR is a unary operator and has the same precedence as the unary + and -
arithmetic operators. It evaluates the immediately following expression for the
parent row of the current row in a hierarchical query.
PRIOR is most commonly used when comparing column values with the equality
operator. (The PRIOR keyword can be on either side of the operator.) PRIOR
causes Oracle to use the value of the parent row in the column. Operators other
than the equal sign (=) are theoretically possible in CONNECT BY clauses. However,
the conditions created by these other operators can result in an infinite loop
through the possible combinations. In this case Oracle detects the loop at run time
and returns an error.
Both the CONNECT BY condition and the PRIOR expression can take the form of an
uncorrelated subquery. However, the PRIOR expression cannot refer to a sequence.
That is, CURRVAL and NEXTVAL are not valid PRIOR expressions.
You can further refine a hierarchical query by using the CONNECT_BY_ROOT operator
to qualify a column in the select list. This operator extends the functionality of the
CONNECT BY [PRIOR] condition of hierarchical queries by returning not only the
immediate parent row but all ancestor rows in the hierarchy.
Oracle processes hierarchical queries as follows:
■ A join, if present, is evaluated first, whether the join is specified in the FROM clause
or with WHERE clause predicates.
■ The CONNECT BY condition is evaluated.
See Also: CONNECT_BY_ROOT on page 4-5 for more information
about this operator and "Hierarchical Query Examples" on page 9-5
START WITH condition
CONNECT BY
NOCYCLE
condition](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-495-320.jpg)
![The UNION [ALL], INTERSECT, MINUS Operators
SQL Queries and Subqueries 9-7
CONNECT BY PRIOR employee_id = manager_id;
Employee Manager Pathlen Path
--------------- ------------ ---------- -----------------------------------
Higgins Kochhar 1 /Kochhar/Higgins
Gietz Kochhar 2 /Kochhar/Higgins/Gietz
Gietz Higgins 1 /Higgins/Gietz
Higgins King 2 /King/Kochhar/Higgins
Gietz King 3 /King/Kochhar/Higgins/Gietz
The following example uses a GROUP BY clause to return the total salary of each
employee in department 110 and all employees below that employee in the hierarchy:
SELECT name, SUM(salary) "Total_Salary" FROM (
SELECT CONNECT_BY_ROOT last_name as name, Salary
FROM employees
WHERE department_id = 110
CONNECT BY PRIOR employee_id = manager_id)
GROUP BY name;
NAME Total_Salary
------------------------- ------------
Gietz 8300
Higgins 20300
King 20300
Kochhar 20300
The UNION [ALL], INTERSECT, MINUS Operators
You can combine multiple queries using the set operators UNION, UNION ALL,
INTERSECT, and MINUS. All set operators have equal precedence. If a SQL statement
contains multiple set operators, then Oracle Database evaluates them from the left to
right unless parentheses explicitly specify another order.
The corresponding expressions in the select lists of the component queries of a
compound query must match in number and must be in the same datatype group
(such as numeric or character).
If component queries select character data, then the datatype of the return values are
determined as follows:
■ If both queries select values of datatype CHAR of equal length, then the returned
values have datatype CHAR of that length. If the queries select values of CHAR with
different lengths, then the returned value is VARCHAR2 with the length of the
larger CHAR value.
■ If either or both of the queries select values of datatype VARCHAR2, then the
returned values have datatype VARCHAR2.
See Also:
■ LEVEL Pseudocolumn on page 3-2 and CONNECT_BY_ISCYCLE
Pseudocolumn on page 3-1 for a discussion of how these
pseudocolumns operate in a hierarchical query
■ SYS_CONNECT_BY_PATH on page 5-176 for information on
retrieving the path of column values from root to node
■ order_by_clause on page 19-28 for more information on the
SIBLINGS keyword of ORDER BY clauses](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-499-320.jpg)
![The UNION [ALL], INTERSECT, MINUS Operators
9-8 Oracle Database SQL Reference
If component queries select numeric data, then the datatype of the return values is
determined by numeric precedence:
■ If any query selects values of type BINARY_DOUBLE, then the returned values
have datatype BINARY_DOUBLE.
■ If no query selects values of type BINARY_DOUBLE but any query selects values of
type BINARY_FLOAT, then the returned values have datatype BINARY_FLOAT.
■ If all queries select values of type NUMBER, then the returned values have datatype
NUMBER.
In queries using set operators, Oracle does not perform implicit conversion across
datatype groups. Therefore, if the corresponding expressions of component queries
resolve to both character data and numeric data, Oracle returns an error.
Examples The following query is valid:
SELECT 3 FROM DUAL
INTERSECT
SELECT 3f FROM DUAL;
This is implicitly converted to the following compound query:
SELECT TO_BINARY_FLOAT(3) FROM DUAL
INTERSECT
SELECT 3f FROM DUAL;
The following query returns an error:
SELECT '3' FROM DUAL
INTERSECT
SELECT 3f FROM DUAL;
Restrictions on the Set Operators The set operators are subject to the following
restrictions:
■ The set operators are not valid on columns of type BLOB, CLOB, BFILE, VARRAY,
or nested table.
■ The UNION, INTERSECT, and MINUS operators are not valid on LONG columns.
■ If the select list preceding the set operator contains an expression, then you must
provide a column alias for the expression in order to refer to it in the order_by_
clause.
■ You cannot also specify the for_update_clause with the set operators.
■ You cannot specify the order_by_clause in the subquery of these operators.
■ You cannot use these operators in SELECT statements containing TABLE collection
expressions.
See Also: Table 2–10, " Implicit Type Conversion Matrix" on
page 2-41 for more information on implicit conversion and "Numeric
Precedence" on page 2-13 for information on numeric precedence
Note: To comply with emerging SQL standards, a future release of
Oracle will give the INTERSECT operator greater precedence than the
other set operators. Therefore, you should use parentheses to specify
order of evaluation in queries that use the INTERSECT operator with
other set operators.](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-500-320.jpg)
![Joins
SQL Queries and Subqueries 9-11
the internal algorithm the optimizer chooses to execute the join, the total size of the
columns in the equijoin condition in a single table may be limited to the size of a data
block minus some overhead. The size of a data block is specified by the initialization
parameter DB_BLOCK_SIZE.
Self Joins
A self join is a join of a table to itself. This table appears twice in the FROM clause and
is followed by table aliases that qualify column names in the join condition. To
perform a self join, Oracle Database combines and returns rows of the table that satisfy
the join condition.
Cartesian Products
If two tables in a join query have no join condition, then Oracle Database returns their
Cartesian product. Oracle combines each row of one table with each row of the other.
A Cartesian product always generates many rows and is rarely useful. For example,
the Cartesian product of two tables, each with 100 rows, has 10,000 rows. Always
include a join condition unless you specifically need a Cartesian product. If a query
joins three or more tables and you do not specify a join condition for a specific pair,
then the optimizer may choose a join order that avoids producing an intermediate
Cartesian product.
Inner Joins
An inner join (sometimes called a simple join) is a join of two or more tables that
returns only those rows that satisfy the join condition.
Outer Joins
An outer join extends the result of a simple join. An outer join returns all rows that
satisfy the join condition and also returns some or all of those rows from one table for
which no rows from the other satisfy the join condition.
■ To write a query that performs an outer join of tables A and B and returns all rows
from A (a left outer join), use the LEFT [OUTER] JOIN syntax in the FROM clause,
or apply the outer join operator (+) to all columns of B in the join condition in the
WHERE clause. For all rows in A that have no matching rows in B, Oracle Database
returns null for any select list expressions containing columns of B.
■ To write a query that performs an outer join of tables A and B and returns all rows
from B (a right outer join), use the RIGHT [OUTER] JOIN syntax in the FROM
clause, or apply the outer join operator (+) to all columns of A in the join condition
in the WHERE clause. For all rows in B that have no matching rows in A, Oracle
returns null for any select list expressions containing columns of A.
■ To write a query that performs an outer join and returns all rows from A and B,
extended with nulls if they do not satisfy the join condition (a full outer join), use
the FULL [OUTER] JOIN syntax in the FROM clause.
You can use outer joins to fill gaps in sparse data. Such a join is called a partitioned
outer join and is formed using the query_partition_clause of the join_clause
syntax. Sparse data is data that does not have rows for all possible values of a
dimension such as time or department. For example, tables of sales data typically do
See Also: "Using Join Queries: Examples" on page 19-38
See Also: "Using Self Joins: Example" on page 19-39](https://image.slidesharecdn.com/oracle10g-book-140322064025-phpapp02/85/Oracle-10-g-Good-one-503-320.jpg)
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Oracle 10 g Good one
- 1. Oracle® Database SQL Reference 10g Release 2 (10.2) B14200-02 December 2005
- 2. Oracle Database SQL Reference, 10g Release 2 (10.2) B14200-02 Copyright © 1996, 2005 Oracle. All rights reserved. Primary Author: Diana Lorentz Contributor: Special thanks to Lex de Haan, who has for over ten years been a great source of information and inspiration in the management of this book. Contributors: Sundeep Abraham, Drew Adams, Patrick Amor, Geeta Arora, Lance Ashdown, Hermann Baer, Vladimir Barriere, Subhransu Basu, Mark Bauer, Tammy Bednar, Eric Belden, Tolga Bozkaya, Bill Bridge, Allen Brumm, Mark Callaghan, Thomas Chang, Timothy Chien, Dinesh Das, Jay Davison, Steve Fogel, Amit Ganesh, John Haydu, Min-Hank Ho, Lilian Hobbs, Chandrasekharan Iyer, Ken Jacobs, Bob Jenkins, Ramkumar Krishnan, Muralidhar Krishnaprasad, Joydip Kundu, Paul Lane, Simon Law, Bill Lee, Geoff Lee, Jeff Levinger, Nina Lewis, Brian Lin, Peter Linsley, Zhen Liu, Bryn Llewellyn, Rich Long, Qianrong Ma, Anand Manikutty, Paul Manning, Robert McGuirk, Jim Melton, Mughees Minhas, Michael Möller, Daniel Morgan, Ari Mozes, Niloy Mukherjee, Chuck Murray, Sujatha Muthulingam, Ananth Raghavan, Kathy Rich, Antonio Romero, John Russell, Vivian Schupmann, Cathy Shea, Vikram Shukla, Bipul Sinha, Mike Stewart, Sankar Subramanian, Srividya Tata, Kathy Taylor, Barry Trute, Randy Urbano, Rama Vissapragada, Douglas Voss, Daniel Wong, Jianping Yang, Adiel Yoaz, Qin Yu, Tsae-Feng Yu, Fred Zemke, Weiran Zhang The Programs (which include both the software and documentation) contain proprietary information; they are provided under a license agreement containing restrictions on use and disclosure and are also protected by copyright, patent, and other intellectual and industrial property laws. Reverse engineering, disassembly, or decompilation of the Programs, except to the extent required to obtain interoperability with other independently created software or as specified by law, is prohibited. The information contained in this document is subject to change without notice. If you find any problems in the documentation, please report them to us in writing. This document is not warranted to be error-free. Except as may be expressly permitted in your license agreement for these Programs, no part of these Programs may be reproduced or transmitted in any form or by any means, electronic or mechanical, for any purpose. If the Programs are delivered to the United States Government or anyone licensing or using the Programs on behalf of the United States Government, the following notice is applicable: U.S. GOVERNMENT RIGHTS Programs, software, databases, and related documentation and technical data delivered to U.S. Government customers are "commercial computer software" or "commercial technical data" pursuant to the applicable Federal Acquisition Regulation and agency-specific supplemental regulations. As such, use, duplication, disclosure, modification, and adaptation of the Programs, including documentation and technical data, shall be subject to the licensing restrictions set forth in the applicable Oracle license agreement, and, to the extent applicable, the additional rights set forth in FAR 52.227-19, Commercial Computer Software—Restricted Rights (June 1987). Oracle Corporation, 500 Oracle Parkway, Redwood City, CA 94065 The Programs are not intended for use in any nuclear, aviation, mass transit, medical, or other inherently dangerous applications. It shall be the licensee's responsibility to take all appropriate fail-safe, backup, redundancy and other measures to ensure the safe use of such applications if the Programs are used for such purposes, and we disclaim liability for any damages caused by such use of the Programs. Oracle, JD Edwards, PeopleSoft, and Retek are registered trademarks of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. The Programs may provide links to Web sites and access to content, products, and services from third parties. Oracle is not responsible for the availability of, or any content provided on, third-party Web sites. You bear all risks associated with the use of such content. If you choose to purchase any products or services from a third party, the relationship is directly between you and the third party. Oracle is not responsible for: (a) the quality of third-party products or services; or (b) fulfilling any of the terms of the agreement with the third party, including delivery of products or services and warranty obligations related to purchased products or services. Oracle is not responsible for any loss or damage of any sort that you may incur from dealing with any third party.
- 3. iii Contents Preface............................................................................................................................................................... xxi Intended Audience.................................................................................................................................... xxi Documentation Accessibility................................................................................................................... xxi Related Documents .................................................................................................................................. xxii Conventions .............................................................................................................................................. xxii What's New in the SQL Reference?............................................................................................... xxiii Oracle Database 10g Release 2 New Features in the SQL Reference............................................... xxiii Oracle Database 10g Release 1 New Features in the SQL Reference............................................... xxv 1 Introduction to Oracle SQL History of SQL ......................................................................................................................................... 1-1 SQL Standards ......................................................................................................................................... 1-1 How SQL Works ............................................................................................................................... 1-2 Common Language for All Relational Databases ......................................................................... 1-3 Recent Enhancements.............................................................................................................................. 1-3 Lexical Conventions................................................................................................................................. 1-3 Tools Support ........................................................................................................................................... 1-4 2 Basic Elements of Oracle SQL Datatypes .................................................................................................................................................. 2-1 Oracle Built-in Datatypes.................................................................................................................. 2-6 CHAR Datatype ......................................................................................................................... 2-8 NCHAR Datatype ...................................................................................................................... 2-9 NVARCHAR2 Datatype ........................................................................................................... 2-9 VARCHAR2 Datatype ............................................................................................................... 2-9 VARCHAR Datatype .............................................................................................................. 2-10 NUMBER Datatype ................................................................................................................ 2-10 Floating-Point Numbers ........................................................................................................ 2-11 BINARY_FLOAT .............................................................................................................. 2-12 BINARY_DOUBLE........................................................................................................... 2-12 Numeric Precedence ............................................................................................................... 2-13 DATE Datatype ....................................................................................................................... 2-16 Using Julian Days ............................................................................................................. 2-16 TIMESTAMP Datatype .......................................................................................................... 2-17
- 4. iv TIMESTAMP WITH TIME ZONE Datatype ....................................................................... 2-17 TIMESTAMP WITH LOCAL TIME ZONE Datatype ........................................................ 2-18 INTERVAL YEAR TO MONTH Datatype .......................................................................... 2-18 INTERVAL DAY TO SECOND Datatype ........................................................................... 2-19 Datetime/Interval Arithmetic ............................................................................................... 2-19 Support for Daylight Saving Times ...................................................................................... 2-21 Datetime and Interval Examples ........................................................................................... 2-22 RAW and LONG RAW Datatypes ....................................................................................... 2-23 BFILE Datatype ....................................................................................................................... 2-26 BLOB Datatype ........................................................................................................................ 2-26 CLOB Datatype ....................................................................................................................... 2-27 NCLOB Datatype .................................................................................................................... 2-27 Restricted Rowids ................................................................................................................... 2-27 Extended Rowids .................................................................................................................... 2-28 Compatibility and Migration ................................................................................................ 2-28 UROWID Datatype ................................................................................................................. 2-28 ANSI, DB2, and SQL/DS Datatypes ........................................................................................... 2-29 User-Defined Types ....................................................................................................................... 2-30 Object Types ............................................................................................................................ 2-30 REF Datatypes ......................................................................................................................... 2-31 Varrays ...................................................................................................................................... 2-31 Nested Tables .......................................................................................................................... 2-31 Oracle-Supplied Types .................................................................................................................. 2-32 Any Types ....................................................................................................................................... 2-32 ANYTYPE ................................................................................................................................. 2-32 ANYDATA................................................................................................................................ 2-32 ANYDATASET......................................................................................................................... 2-32 XML Types ...................................................................................................................................... 2-33 XMLType .................................................................................................................................. 2-33 URI Datatypes ......................................................................................................................... 2-33 URIFactory Package ................................................................................................................ 2-34 Spatial Types ................................................................................................................................... 2-34 SDO_GEOMETRY ................................................................................................................... 2-35 SDO_TOPO_GEOMETRY ..................................................................................................... 2-35 SDO_GEORASTER.................................................................................................................. 2-35 Media Types .................................................................................................................................... 2-35 ORDAudio ............................................................................................................................... 2-36 ORDImage ................................................................................................................................ 2-36 ORDImageSignature ............................................................................................................... 2-36 ORDVideo ................................................................................................................................ 2-36 ORDDoc .................................................................................................................................... 2-36 SI_StillImage ............................................................................................................................ 2-36 SI_Color .................................................................................................................................... 2-36 SI_AverageColor ..................................................................................................................... 2-36 SI_ColorHistogram ................................................................................................................. 2-36 SI_PositionalColor .................................................................................................................. 2-36 SI_Texture ................................................................................................................................ 2-36
- 5. v SI_FeatureList .......................................................................................................................... 2-37 Expression Filter Type.................................................................................................................... 2-37 Expression................................................................................................................................. 2-37 Datatype Comparison Rules .............................................................................................................. 2-37 Numeric Values .............................................................................................................................. 2-37 Date Values ..................................................................................................................................... 2-37 Character Values ............................................................................................................................ 2-37 Object Values .................................................................................................................................. 2-40 Varrays and Nested Tables ........................................................................................................... 2-40 Data Conversion ............................................................................................................................. 2-40 Implicit and Explicit Data Conversion ................................................................................ 2-40 Implicit Data Conversion ....................................................................................................... 2-41 Implicit Data Conversion Examples...................................................................................... 2-43 Explicit Data Conversion ....................................................................................................... 2-43 Literals .................................................................................................................................................... 2-44 Text Literals ..................................................................................................................................... 2-45 Numeric Literals ............................................................................................................................. 2-46 Integer Literals ......................................................................................................................... 2-46 NUMBER and Floating-Point Literals .................................................................................. 2-47 Datetime Literals ............................................................................................................................ 2-49 Interval Literals................................................................................................................................ 2-51 INTERVAL YEAR TO MONTH ............................................................................................ 2-52 INTERVAL DAY TO SECOND ............................................................................................. 2-53 Format Models ...................................................................................................................................... 2-54 Number Format Models ................................................................................................................ 2-55 Number Format Elements ..................................................................................................... 2-56 Datetime Format Models .............................................................................................................. 2-58 Datetime Format Elements .................................................................................................... 2-59 Uppercase Letters in Date Format Elements ............................................................... 2-59 Punctuation and Character Literals in Datetime Format Models ............................. 2-59 Datetime Format Elements and Globalization Support .................................................... 2-62 ISO Standard Date Format Elements ................................................................................... 2-62 The RR Datetime Format Element ........................................................................................ 2-63 RR Datetime Format Examples....................................................................................... 2-63 Datetime Format Element Suffixes ....................................................................................... 2-64 Format Model Modifiers ............................................................................................................... 2-64 Format Model Examples......................................................................................................... 2-65 String-to-Date Conversion Rules ................................................................................................. 2-67 XML Format Model ....................................................................................................................... 2-67 Nulls ........................................................................................................................................................ 2-68 Nulls in SQL Functions ................................................................................................................. 2-69 Nulls with Comparison Conditions ............................................................................................ 2-69 Nulls in Conditions ........................................................................................................................ 2-69 Comments .............................................................................................................................................. 2-70 Comments Within SQL Statements ............................................................................................. 2-70 Comments on Schema Objects ..................................................................................................... 2-71 Using Hints ..................................................................................................................................... 2-71
- 6. vi Alphabetical Listing of Hints ........................................................................................................ 2-75 ALL_ROWS Hint .................................................................................................................... 2-75 APPEND Hint .......................................................................................................................... 2-75 CACHE Hint ............................................................................................................................ 2-76 CLUSTER Hint ........................................................................................................................ 2-76 CURSOR_SHARING_EXACT Hint ..................................................................................... 2-76 DRIVING_SITE Hint .............................................................................................................. 2-77 DYNAMIC_SAMPLING Hint ............................................................................................... 2-77 FACT Hint ................................................................................................................................ 2-78 FIRST_ROWS Hint .................................................................................................................. 2-78 FULL Hint ................................................................................................................................ 2-78 HASH Hint .............................................................................................................................. 2-79 INDEX Hint ............................................................................................................................. 2-79 INDEX_ASC Hint ................................................................................................................... 2-80 INDEX_COMBINE Hint ....................................................................................................... 2-80 INDEX_DESC Hint ................................................................................................................. 2-80 INDEX_FFS Hint ..................................................................................................................... 2-81 INDEX_JOIN Hint .................................................................................................................. 2-81 INDEX_SS Hint ....................................................................................................................... 2-81 INDEX_SS_ASC Hint ............................................................................................................. 2-82 INDEX_SS_DESC Hint ........................................................................................................... 2-82 LEADING Hint ........................................................................................................................ 2-83 MERGE Hint ............................................................................................................................ 2-83 MODEL_MIN_ANALYSIS Hint ........................................................................................... 2-83 NOAPPEND Hint ................................................................................................................... 2-84 NOCACHE Hint ..................................................................................................................... 2-84 NO_EXPAND Hint ................................................................................................................. 2-84 NO_FACT Hint ....................................................................................................................... 2-85 NO_INDEX Hint ..................................................................................................................... 2-85 NO_INDEX_FFS Hint ............................................................................................................ 2-85 NO_INDEX_SS Hint ............................................................................................................... 2-86 NO_MERGE Hint ................................................................................................................... 2-86 NO_PARALLEL Hint ............................................................................................................. 2-86 NOPARALLEL Hint................................................................................................................ 2-87 NO_PARALLEL_INDEX Hint .............................................................................................. 2-87 NOPARALLEL_INDEX Hint................................................................................................. 2-87 NO_PUSH_PRED Hint .......................................................................................................... 2-87 NO_PUSH_SUBQ Hint .......................................................................................................... 2-87 NO_PX_JOIN_FILTER Hint .................................................................................................. 2-88 NO_REWRITE Hint ................................................................................................................ 2-88 NOREWRITE Hint................................................................................................................... 2-88 NO_QUERY_TRANSFORMATION Hint ........................................................................... 2-88 NO_STAR_TRANSFORMATION Hint ............................................................................... 2-88 NO_UNNEST Hint ................................................................................................................. 2-88 NO_USE_HASH Hint ............................................................................................................ 2-89 NO_USE_MERGE Hint .......................................................................................................... 2-89 NO_USE_NL Hint .................................................................................................................. 2-89
- 7. vii NO_XML_QUERY_REWRITE Hint...................................................................................... 2-89 ORDERED Hint ....................................................................................................................... 2-90 PARALLEL Hint ..................................................................................................................... 2-90 PARALLEL_INDEX Hint ...................................................................................................... 2-91 PQ_DISTRIBUTE Hint ........................................................................................................... 2-91 PUSH_PRED Hint ................................................................................................................... 2-92 PUSH_SUBQ Hint ................................................................................................................... 2-93 PX_JOIN_FILTER Hint ........................................................................................................... 2-93 QB_NAME Hint ...................................................................................................................... 2-93 REWRITE Hint ........................................................................................................................ 2-94 RULE Hint ................................................................................................................................ 2-94 STAR_TRANSFORMATION Hint ....................................................................................... 2-94 UNNEST Hint .......................................................................................................................... 2-95 USE_CONCAT Hint ............................................................................................................... 2-95 USE_HASH Hint ..................................................................................................................... 2-96 USE_MERGE Hint .................................................................................................................. 2-96 USE_NL Hint ........................................................................................................................... 2-96 USE_NL_WITH_INDEX Hint ............................................................................................... 2-97 Database Objects................................................................................................................................... 2-97 Schema Objects ............................................................................................................................... 2-97 Nonschema Objects ........................................................................................................................ 2-98 Schema Object Names and Qualifiers ............................................................................................. 2-98 Schema Object Naming Rules ...................................................................................................... 2-98 Schema Object Naming Examples ............................................................................................. 2-101 Schema Object Naming Guidelines ........................................................................................... 2-102 Syntax for Schema Objects and Parts in SQL Statements........................................................... 2-102 How Oracle Database Resolves Schema Object References ................................................... 2-103 Referring to Objects in Other Schemas ..................................................................................... 2-104 Referring to Objects in Remote Databases ................................................................................ 2-104 Creating Database Links ...................................................................................................... 2-104 Database Link Names .................................................................................................... 2-104 Username and Password............................................................................................... 2-105 Database Connect String................................................................................................ 2-105 Referring to Database Links ................................................................................................ 2-105 Referring to Partitioned Tables and Indexes ............................................................................ 2-106 Referring to Object Type Attributes and Methods................................................................... 2-107 3 Pseudocolumns Hierarchical Query Pseudocolumns .................................................................................................... 3-1 CONNECT_BY_ISCYCLE Pseudocolumn .................................................................................... 3-1 CONNECT_BY_ISLEAF Pseudocolumn ....................................................................................... 3-2 LEVEL Pseudocolumn ...................................................................................................................... 3-2 Sequence Pseudocolumns ..................................................................................................................... 3-3 Where to Use Sequence Values ....................................................................................................... 3-3 How to Use Sequence Values .......................................................................................................... 3-4 Version Query Pseudocolumns ............................................................................................................ 3-5 COLUMN_VALUE Pseudocolumn ...................................................................................................... 3-6
- 8. viii OBJECT_ID Pseudocolumn .................................................................................................................. 3-7 OBJECT_VALUE Pseudocolumn .......................................................................................................... 3-7 ORA_ROWSCN Pseudocolumn ........................................................................................................... 3-8 ROWID Pseudocolumn .......................................................................................................................... 3-8 ROWNUM Pseudocolumn .................................................................................................................... 3-9 XMLDATA Pseudocolumn ................................................................................................................. 3-10 4 Operators About SQL Operators.............................................................................................................................. 4-1 Unary and Binary Operators ........................................................................................................... 4-2 Operator Precedence ......................................................................................................................... 4-2 Arithmetic Operators .............................................................................................................................. 4-3 Concatenation Operator.......................................................................................................................... 4-3 Hierarchical Query Operators................................................................................................................ 4-5 PRIOR ................................................................................................................................................. 4-5 CONNECT_BY_ROOT ..................................................................................................................... 4-5 Set Operators ............................................................................................................................................ 4-5 Multiset Operators .................................................................................................................................. 4-5 MULTISET EXCEPT ......................................................................................................................... 4-6 MULTISET INTERSECT .................................................................................................................. 4-7 MULTISET UNION .......................................................................................................................... 4-8 User-Defined Operators ......................................................................................................................... 4-9 5 Functions SQL Functions .......................................................................................................................................... 5-1 Single-Row Functions ....................................................................................................................... 5-3 Numeric Functions .................................................................................................................... 5-3 Character Functions Returning Character Values ................................................................ 5-3 NLS Character Functions .......................................................................................................... 5-4 Character Functions Returning Number Values ................................................................... 5-4 Datetime Functions .................................................................................................................... 5-4 General Comparison Functions ............................................................................................... 5-5 Conversion Functions ................................................................................................................ 5-5 Large Object Functions .............................................................................................................. 5-6 Collection Functions .................................................................................................................. 5-6 Hierarchical Function ................................................................................................................ 5-6 Data Mining Functions .............................................................................................................. 5-6 XML Functions ........................................................................................................................... 5-7 Encoding and Decoding Functions ......................................................................................... 5-7 NULL-Related Functions .......................................................................................................... 5-7 Environment and Identifier Functions ................................................................................... 5-8 Aggregate Functions ......................................................................................................................... 5-8 Analytic Functions ............................................................................................................................ 5-9 Object Reference Functions ........................................................................................................... 5-14 Model Functions ............................................................................................................................. 5-15 Alphabetical Listing of SQL Functions ........................................................................................ 5-15 ABS .......................................................................................................................................................... 5-15
- 9. ix ACOS ...................................................................................................................................................... 5-16 ADD_MONTHS ................................................................................................................................... 5-16 APPENDCHILDXML .......................................................................................................................... 5-17 ASCIISTR .............................................................................................................................................. 5-18 ASCII ...................................................................................................................................................... 5-18 ASIN ....................................................................................................................................................... 5-19 ATAN ...................................................................................................................................................... 5-19 ATAN2 .................................................................................................................................................... 5-20 AVG ......................................................................................................................................................... 5-20 BFILENAME .......................................................................................................................................... 5-21 BIN_TO_NUM ...................................................................................................................................... 5-22 BITAND .................................................................................................................................................. 5-23 CARDINALITY .................................................................................................................................... 5-24 CAST ....................................................................................................................................................... 5-24 CEIL ......................................................................................................................................................... 5-27 CHARTOROWID ................................................................................................................................. 5-27 CHR ......................................................................................................................................................... 5-28 CLUSTER_ID ........................................................................................................................................ 5-29 CLUSTER_PROBABILITY ................................................................................................................. 5-30 CLUSTER_SET ..................................................................................................................................... 5-32 COALESCE ............................................................................................................................................ 5-34 COLLECT ............................................................................................................................................... 5-35 COMPOSE ............................................................................................................................................. 5-36 CONCAT ................................................................................................................................................ 5-36 CONVERT ............................................................................................................................................. 5-37 CORR ...................................................................................................................................................... 5-38 CORR_* .................................................................................................................................................. 5-39 CORR_S ........................................................................................................................................... 5-40 CORR_K .......................................................................................................................................... 5-41 COS ......................................................................................................................................................... 5-41 COSH ...................................................................................................................................................... 5-42 COUNT ................................................................................................................................................... 5-42 COVAR_POP ......................................................................................................................................... 5-44 COVAR_SAMP ..................................................................................................................................... 5-45 CUME_DIST ......................................................................................................................................... 5-46 CURRENT_DATE ................................................................................................................................ 5-47 CURRENT_TIMESTAMP ................................................................................................................... 5-48 CV............................................................................................................................................................. 5-49 DBTIMEZONE ..................................................................................................................................... 5-50 DECODE ................................................................................................................................................ 5-51 DECOMPOSE ....................................................................................................................................... 5-52 DELETEXML ......................................................................................................................................... 5-53 DENSE_RANK ..................................................................................................................................... 5-54 DEPTH .................................................................................................................................................... 5-55 DEREF ..................................................................................................................................................... 5-56 DUMP ..................................................................................................................................................... 5-57 EMPTY_BLOB, EMPTY_CLOB ......................................................................................................... 5-58
- 10. x EXISTSNODE ....................................................................................................................................... 5-58 EXP .......................................................................................................................................................... 5-59 EXTRACT (datetime) ........................................................................................................................... 5-60 EXTRACT (XML) .................................................................................................................................. 5-62 EXTRACTVALUE ................................................................................................................................. 5-63 FEATURE_ID ........................................................................................................................................ 5-63 FEATURE_SET ...................................................................................................................................... 5-65 FEATURE_VALUE ................................................................................................................................ 5-67 FIRST ...................................................................................................................................................... 5-68 FIRST_VALUE ...................................................................................................................................... 5-70 FLOOR .................................................................................................................................................... 5-71 FROM_TZ .............................................................................................................................................. 5-71 GREATEST ............................................................................................................................................ 5-72 GROUP_ID ............................................................................................................................................ 5-72 GROUPING ........................................................................................................................................... 5-73 GROUPING_ID .................................................................................................................................... 5-74 HEXTORAW .......................................................................................................................................... 5-75 INITCAP ................................................................................................................................................ 5-76 INSERTCHILDXML ............................................................................................................................ 5-76 INSERTXMLBEFORE .......................................................................................................................... 5-78 INSTR ..................................................................................................................................................... 5-79 ITERATION_NUMBER ...................................................................................................................... 5-80 LAG ......................................................................................................................................................... 5-81 LAST ....................................................................................................................................................... 5-82 LAST_DAY ............................................................................................................................................. 5-83 LAST_VALUE ........................................................................................................................................ 5-83 LEAD ....................................................................................................................................................... 5-85 LEAST ..................................................................................................................................................... 5-86 LENGTH ................................................................................................................................................ 5-86 LN ............................................................................................................................................................ 5-87 LNNVL ................................................................................................................................................... 5-88 LOCALTIMESTAMP ........................................................................................................................... 5-89 LOG ......................................................................................................................................................... 5-90 LOWER ................................................................................................................................................... 5-90 LPAD........................................................................................................................................................ 5-91 LTRIM ..................................................................................................................................................... 5-91 MAKE_REF ............................................................................................................................................ 5-92 MAX ........................................................................................................................................................ 5-93 MEDIAN ................................................................................................................................................ 5-94 MIN ......................................................................................................................................................... 5-96 MOD ....................................................................................................................................................... 5-97 MONTHS_BETWEEN ......................................................................................................................... 5-98 NANVL ................................................................................................................................................... 5-98 NCHR ..................................................................................................................................................... 5-99 NEW_TIME ......................................................................................................................................... 5-100 NEXT_DAY .......................................................................................................................................... 5-101 NLS_CHARSET_DECL_LEN ........................................................................................................... 5-101
- 11. xi NLS_CHARSET_ID ........................................................................................................................... 5-102 NLS_CHARSET_NAME ................................................................................................................... 5-102 NLS_INITCAP .................................................................................................................................... 5-103 NLS_LOWER ....................................................................................................................................... 5-104 NLSSORT ............................................................................................................................................. 5-104 NLS_UPPER ........................................................................................................................................ 5-106 NTILE ................................................................................................................................................... 5-106 NULLIF ................................................................................................................................................. 5-107 NUMTODSINTERVAL ..................................................................................................................... 5-108 NUMTOYMINTERVAL .................................................................................................................... 5-109 NVL ....................................................................................................................................................... 5-110 NVL2 ..................................................................................................................................................... 5-111 ORA_HASH ........................................................................................................................................ 5-112 PATH...................................................................................................................................................... 5-112 PERCENT_RANK .............................................................................................................................. 5-113 PERCENTILE_CONT ........................................................................................................................ 5-114 PERCENTILE_DISC .......................................................................................................................... 5-116 POWER ................................................................................................................................................. 5-118 POWERMULTISET ............................................................................................................................ 5-118 POWERMULTISET_BY_CARDINALITY ..................................................................................... 5-119 PREDICTION ..................................................................................................................................... 5-120 PREDICTION_COST ........................................................................................................................ 5-122 PREDICTION_DETAILS .................................................................................................................. 5-123 PREDICTION_PROBABILITY ....................................................................................................... 5-124 PREDICTION_SET ............................................................................................................................ 5-126 PRESENTNNV .................................................................................................................................... 5-128 PRESENTV ........................................................................................................................................... 5-129 PREVIOUS ........................................................................................................................................... 5-130 RANK ................................................................................................................................................... 5-131 RATIO_TO_REPORT ........................................................................................................................ 5-133 RAWTOHEX ........................................................................................................................................ 5-133 RAWTONHEX .................................................................................................................................... 5-134 REF ........................................................................................................................................................ 5-134 REFTOHEX .......................................................................................................................................... 5-135 REGEXP_INSTR ................................................................................................................................. 5-136 REGEXP_REPLACE ........................................................................................................................... 5-138 REGEXP_SUBSTR ............................................................................................................................. 5-140 REGR_ (Linear Regression) Functions ........................................................................................... 5-142 REMAINDER ...................................................................................................................................... 5-147 REPLACE ............................................................................................................................................. 5-148 ROUND (number) .............................................................................................................................. 5-148 ROUND (date) .................................................................................................................................... 5-149 ROW_NUMBER ................................................................................................................................. 5-150 ROWIDTOCHAR ............................................................................................................................... 5-151 ROWIDTONCHAR ........................................................................................................................... 5-151 RPAD .................................................................................................................................................... 5-152 RTRIM .................................................................................................................................................. 5-153
- 12. xii SCN_TO_TIMESTAMP .................................................................................................................... 5-153 SESSIONTIMEZONE ....................................................................................................................... 5-154 SET ........................................................................................................................................................ 5-155 SIGN ..................................................................................................................................................... 5-155 SIN ......................................................................................................................................................... 5-156 SINH ..................................................................................................................................................... 5-156 SOUNDEX ........................................................................................................................................... 5-157 SQRT ..................................................................................................................................................... 5-158 STATS_BINOMIAL_TEST ............................................................................................................... 5-159 STATS_CROSSTAB ........................................................................................................................... 5-160 STATS_F_TEST ................................................................................................................................... 5-161 STATS_KS_TEST ................................................................................................................................ 5-162 STATS_MODE .................................................................................................................................... 5-162 STATS_MW_TEST ............................................................................................................................. 5-164 STATS_ONE_WAY_ANOVA ............................................................................................................ 5-165 STATS_T_TEST_* ............................................................................................................................... 5-166 STATS_T_TEST_ONE .................................................................................................................. 5-167 STATS_T_TEST_PAIRED ........................................................................................................... 5-167 STATS_T_TEST_INDEP and STATS_T_TEST_INDEPU ....................................................... 5-168 STATS_WSR_TEST ............................................................................................................................ 5-169 STDDEV ............................................................................................................................................... 5-170 STDDEV_POP .................................................................................................................................... 5-171 STDDEV_SAMP ................................................................................................................................. 5-172 SUBSTR ................................................................................................................................................ 5-173 SUM ...................................................................................................................................................... 5-174 SYS_CONNECT_BY_PATH ............................................................................................................. 5-176 SYS_CONTEXT .................................................................................................................................. 5-176 SYS_DBURIGEN ................................................................................................................................ 5-181 SYS_EXTRACT_UTC ........................................................................................................................ 5-182 SYS_GUID ........................................................................................................................................... 5-182 SYS_TYPEID ....................................................................................................................................... 5-183 SYS_XMLAGG ................................................................................................................................... 5-184 SYS_XMLGEN .................................................................................................................................... 5-185 SYSDATE ............................................................................................................................................. 5-185 SYSTIMESTAMP ............................................................................................................................... 5-186 TAN ....................................................................................................................................................... 5-186 TANH .................................................................................................................................................... 5-187 TIMESTAMP_TO_SCN .................................................................................................................... 5-187 TO_BINARY_DOUBLE ..................................................................................................................... 5-188 TO_BINARY_FLOAT ........................................................................................................................ 5-189 TO_CHAR (character) ........................................................................................................................ 5-190 TO_CHAR (datetime) ........................................................................................................................ 5-191 TO_CHAR (number) .......................................................................................................................... 5-193 TO_CLOB ............................................................................................................................................. 5-194 TO_DATE ............................................................................................................................................. 5-195 TO_DSINTERVAL ............................................................................................................................. 5-196 TO_LOB ............................................................................................................................................... 5-196
- 13. xiii TO_MULTI_BYTE .............................................................................................................................. 5-197 TO_NCHAR (character) .................................................................................................................... 5-198 TO_NCHAR (datetime) ..................................................................................................................... 5-198 TO_NCHAR (number) ...................................................................................................................... 5-199 TO_NCLOB ......................................................................................................................................... 5-199 TO_NUMBER ..................................................................................................................................... 5-200 TO_SINGLE_BYTE ............................................................................................................................ 5-201 TO_TIMESTAMP ............................................................................................................................... 5-201 TO_TIMESTAMP_TZ ........................................................................................................................ 5-202 TO_YMINTERVAL ........................................................................................................................... 5-203 TRANSLATE ....................................................................................................................................... 5-203 TRANSLATE ... USING .................................................................................................................... 5-204 TREAT .................................................................................................................................................. 5-206 TRIM ..................................................................................................................................................... 5-207 TRUNC (number) ............................................................................................................................... 5-208 TRUNC (date) ...................................................................................................................................... 5-208 TZ_OFFSET ......................................................................................................................................... 5-209 UID ........................................................................................................................................................ 5-210 UNISTR ................................................................................................................................................ 5-210 UPDATEXML ...................................................................................................................................... 5-211 UPPER ................................................................................................................................................... 5-212 USER ..................................................................................................................................................... 5-212 USERENV ............................................................................................................................................ 5-213 VALUE .................................................................................................................................................. 5-214 VAR_POP ............................................................................................................................................. 5-214 VAR_SAMP ......................................................................................................................................... 5-216 VARIANCE .......................................................................................................................................... 5-216 VSIZE .................................................................................................................................................... 5-218 WIDTH_BUCKET .............................................................................................................................. 5-218 XMLAGG ............................................................................................................................................. 5-220 XMLCDATA ........................................................................................................................................ 5-221 XMLCOLATTVAL............................................................................................................................... 5-222 XMLCOMMENT ................................................................................................................................ 5-223 XMLCONCAT ..................................................................................................................................... 5-223 XMLELEMENT.................................................................................................................................... 5-224 XMLFOREST ....................................................................................................................................... 5-226 XMLPARSE .......................................................................................................................................... 5-227 XMLPI ................................................................................................................................................... 5-228 XMLQUERY ......................................................................................................................................... 5-228 XMLROOT ........................................................................................................................................... 5-230 XMLSEQUENCE ................................................................................................................................. 5-230 XMLSERIALIZE ................................................................................................................................. 5-232 XMLTABLE .......................................................................................................................................... 5-232 XMLTRANSFORM ............................................................................................................................. 5-234 ROUND and TRUNC Date Functions ............................................................................................ 5-235 User-Defined Functions .................................................................................................................... 5-236 Prerequisites................................................................................................................................... 5-237
- 14. xiv Name Precedence ......................................................................................................................... 5-237 Naming Conventions ........................................................................................................... 5-238 6 Expressions About SQL Expressions ......................................................................................................................... 6-1 Simple Expressions ................................................................................................................................. 6-3 Compound Expressions ......................................................................................................................... 6-4 CASE Expressions ................................................................................................................................... 6-5 CURSOR Expressions.............................................................................................................................. 6-6 Datetime Expressions ............................................................................................................................. 6-8 Function Expressions .............................................................................................................................. 6-9 Interval Expressions ............................................................................................................................. 6-10 Object Access Expressions .................................................................................................................. 6-10 Scalar Subquery Expressions ............................................................................................................. 6-11 Model Expressions ................................................................................................................................ 6-11 Type Constructor Expressions ............................................................................................................ 6-13 Variable Expressions ............................................................................................................................ 6-15 Expression Lists .................................................................................................................................... 6-15 7 Conditions About SQL Conditions............................................................................................................................ 7-1 Condition Precedence........................................................................................................................ 7-3 Comparison Conditions ......................................................................................................................... 7-4 Simple Comparison Conditions ...................................................................................................... 7-5 Group Comparison Conditions ....................................................................................................... 7-6 Floating-Point Conditions ..................................................................................................................... 7-7 Logical Conditions ................................................................................................................................... 7-7 Model Conditions ................................................................................................................................... 7-9 IS ANY Condition ............................................................................................................................. 7-9 IS PRESENT Condition ................................................................................................................. 7-10 Multiset Conditions ............................................................................................................................. 7-11 IS A SET Condition ........................................................................................................................ 7-11 IS EMPTY Condition ...................................................................................................................... 7-11 MEMBER Condition ...................................................................................................................... 7-12 SUBMULTISET Condition ............................................................................................................ 7-13 Pattern-matching Conditions ............................................................................................................. 7-14 LIKE Condition ............................................................................................................................... 7-14 REGEXP_LIKE Condition ............................................................................................................. 7-17 Range Conditions ................................................................................................................................. 7-18 Null Conditions .................................................................................................................................... 7-19 XML Conditions ................................................................................................................................... 7-19 EQUALS_PATH Condition .......................................................................................................... 7-19 UNDER_PATH Condition ............................................................................................................ 7-20 Compound Conditions ........................................................................................................................ 7-21 EXISTS Condition ................................................................................................................................ 7-21 IN Condition ........................................................................................................................................ 7-21 IS OF type Condition ........................................................................................................................... 7-23
- 15. xv 8 Common SQL DDL Clauses allocate_extent_clause ............................................................................................................................ 8-2 constraint .................................................................................................................................................. 8-4 deallocate_unused_clause .................................................................................................................... 8-26 file_specification ................................................................................................................................... 8-28 logging_clause ........................................................................................................................................ 8-36 parallel_clause ....................................................................................................................................... 8-39 physical_attributes_clause .................................................................................................................. 8-42 size_clause ............................................................................................................................................. 8-45 storage_clause ........................................................................................................................................ 8-46 9 SQL Queries and Subqueries About Queries and Subqueries ............................................................................................................ 9-1 Creating Simple Queries ........................................................................................................................ 9-2 Hierarchical Queries ............................................................................................................................... 9-2 Hierarchical Query Examples .......................................................................................................... 9-5 The UNION [ALL], INTERSECT, MINUS Operators....................................................................... 9-7 Sorting Query Results ............................................................................................................................ 9-9 Joins ......................................................................................................................................................... 9-10 Join Conditions ............................................................................................................................... 9-10 Equijoins .......................................................................................................................................... 9-10 Self Joins .......................................................................................................................................... 9-11 Cartesian Products ......................................................................................................................... 9-11 Inner Joins ....................................................................................................................................... 9-11 Outer Joins ....................................................................................................................................... 9-11 Antijoins .......................................................................................................................................... 9-13 Semijoins .......................................................................................................................................... 9-13 Using Subqueries ................................................................................................................................. 9-13 Unnesting of Nested Subqueries ...................................................................................................... 9-14 Selecting from the DUAL Table ........................................................................................................ 9-15 Distributed Queries ............................................................................................................................. 9-15 10 SQL Statements: ALTER CLUSTER to ALTER JAVA Types of SQL Statements .................................................................................................................... 10-1 Data Definition Language (DDL) Statements ............................................................................ 10-1 Data Manipulation Language (DML) Statements ..................................................................... 10-2 Transaction Control Statements ................................................................................................... 10-3 Session Control Statements ........................................................................................................... 10-3 System Control Statement ............................................................................................................. 10-3 Embedded SQL Statements .......................................................................................................... 10-3 How the SQL Statement Chapters are Organized ......................................................................... 10-3 ALTER CLUSTER ................................................................................................................................. 10-5 ALTER DATABASE ............................................................................................................................. 10-9 ALTER DIMENSION ........................................................................................................................ 10-45 ALTER DISKGROUP ........................................................................................................................ 10-48 ALTER FUNCTION ........................................................................................................................... 10-61
- 16. xvi ALTER INDEX .................................................................................................................................... 10-64 ALTER INDEXTYPE .......................................................................................................................... 10-82 ALTER JAVA ........................................................................................................................................ 10-84 11 SQL Statements: ALTER MATERIALIZED VIEW to ALTER SYSTEM ALTER MATERIALIZED VIEW ........................................................................................................ 11-2 ALTER MATERIALIZED VIEW LOG ............................................................................................ 11-15 ALTER OPERATOR ........................................................................................................................... 11-21 ALTER OUTLINE ............................................................................................................................... 11-24 ALTER PACKAGE ............................................................................................................................. 11-26 ALTER PROCEDURE ........................................................................................................................ 11-29 ALTER PROFILE ................................................................................................................................ 11-32 ALTER RESOURCE COST ............................................................................................................... 11-35 ALTER ROLE ....................................................................................................................................... 11-38 ALTER ROLLBACK SEGMENT ..................................................................................................... 11-40 ALTER SEQUENCE ........................................................................................................................... 11-43 ALTER SESSION ................................................................................................................................ 11-45 Initialization Parameters and ALTER SESSION....................................................................... 11-50 Session Parameters and ALTER SESSION ............................................................................... 11-53 ALTER SYSTEM ................................................................................................................................. 11-60 Initialization Parameters and ALTER SYSTEM........................................................................ 11-72 System Parameters and ALTER SYSTEM.................................................................................. 11-83 Shared Server Parameters .................................................................................................... 11-83 12 SQL Statements: ALTER TABLE to ALTER TABLESPACE ALTER TABLE ....................................................................................................................................... 12-2 ALTER TABLESPACE ........................................................................................................................ 12-79 13 SQL Statements: ALTER TRIGGER to COMMIT ALTER TRIGGER ................................................................................................................................. 13-2 ALTER TYPE ......................................................................................................................................... 13-5 ALTER USER ....................................................................................................................................... 13-18 ALTER VIEW ....................................................................................................................................... 13-25 ANALYZE ............................................................................................................................................ 13-27 ASSOCIATE STATISTICS ................................................................................................................ 13-38 AUDIT .................................................................................................................................................. 13-42 CALL ..................................................................................................................................................... 13-53 COMMENT ......................................................................................................................................... 13-57 COMMIT ............................................................................................................................................. 13-59 14 SQL Statements: CREATE CLUSTER to CREATE JAVA CREATE CLUSTER .............................................................................................................................. 14-2 CREATE CONTEXT ............................................................................................................................. 14-9 CREATE CONTROLFILE ................................................................................................................. 14-12 CREATE DATABASE ......................................................................................................................... 14-18 CREATE DATABASE LINK ............................................................................................................. 14-31
- 17. xvii CREATE DIMENSION ..................................................................................................................... 14-36 CREATE DIRECTORY ...................................................................................................................... 14-42 CREATE DISKGROUP ..................................................................................................................... 14-44 CREATE FUNCTION ........................................................................................................................ 14-48 CREATE INDEX ................................................................................................................................. 14-58 CREATE INDEXTYPE ....................................................................................................................... 14-81 CREATE JAVA ..................................................................................................................................... 14-84 15 SQL Statements: CREATE LIBRARY to CREATE SPFILE CREATE LIBRARY ............................................................................................................................... 15-2 CREATE MATERIALIZED VIEW ..................................................................................................... 15-4 CREATE MATERIALIZED VIEW LOG ......................................................................................... 15-25 CREATE OPERATOR ........................................................................................................................ 15-32 CREATE OUTLINE ............................................................................................................................ 15-35 CREATE PACKAGE ........................................................................................................................... 15-39 CREATE PACKAGE BODY .............................................................................................................. 15-43 CREATE PFILE .................................................................................................................................... 15-47 CREATE PROCEDURE ..................................................................................................................... 15-49 CREATE PROFILE ............................................................................................................................. 15-54 CREATE RESTORE POINT ............................................................................................................. 15-60 CREATE ROLE .................................................................................................................................... 15-63 CREATE ROLLBACK SEGMENT .................................................................................................. 15-66 CREATE SCHEMA ............................................................................................................................. 15-69 CREATE SEQUENCE ........................................................................................................................ 15-71 CREATE SPFILE ................................................................................................................................. 15-75 16 SQL Statements: CREATE SYNONYM to CREATE TRIGGER CREATE SYNONYM ........................................................................................................................... 16-2 CREATE TABLE .................................................................................................................................... 16-6 CREATE TABLESPACE ..................................................................................................................... 16-61 CREATE TRIGGER ............................................................................................................................ 16-75 17 SQL Statements: CREATE TYPE to DROP ROLLBACK SEGMENT CREATE TYPE ....................................................................................................................................... 17-3 CREATE TYPE BODY ........................................................................................................................ 17-21 CREATE USER .................................................................................................................................... 17-26 CREATE VIEW .................................................................................................................................... 17-32 DELETE ................................................................................................................................................ 17-43 DISASSOCIATE STATISTICS ........................................................................................................ 17-51 DROP CLUSTER ................................................................................................................................ 17-53 DROP CONTEXT ............................................................................................................................... 17-55 DROP DATABASE ............................................................................................................................. 17-56 DROP DATABASE LINK ................................................................................................................. 17-57 DROP DIMENSION .......................................................................................................................... 17-58 DROP DIRECTORY .......................................................................................................................... 17-59 DROP DISKGROUP ......................................................................................................................... 17-60
- 18. xviii DROP FUNCTION ............................................................................................................................ 17-62 DROP INDEX....................................................................................................................................... 17-64 DROP INDEXTYPE ........................................................................................................................... 17-66 DROP JAVA ......................................................................................................................................... 17-67 DROP LIBRARY ................................................................................................................................. 17-68 DROP MATERIALIZED VIEW........................................................................................................ 17-69 DROP MATERIALIZED VIEW LOG ............................................................................................. 17-71 DROP OPERATOR ............................................................................................................................ 17-73 DROP OUTLINE ................................................................................................................................ 17-74 DROP PACKAGE ............................................................................................................................... 17-75 DROP PROCEDURE ......................................................................................................................... 17-77 DROP PROFILE .................................................................................................................................. 17-78 DROP RESTORE POINT ................................................................................................................. 17-79 DROP ROLE ........................................................................................................................................ 17-80 DROP ROLLBACK SEGMENT ...................................................................................................... 17-81 18 SQL Statements: DROP SEQUENCE to ROLLBACK DROP SEQUENCE .............................................................................................................................. 18-2 DROP SYNONYM ............................................................................................................................... 18-3 DROP TABLE ........................................................................................................................................ 18-5 DROP TABLESPACE ........................................................................................................................... 18-9 DROP TRIGGER................................................................................................................................. 18-12 DROP TYPE ......................................................................................................................................... 18-13 DROP TYPE BODY ............................................................................................................................ 18-15 DROP USER ........................................................................................................................................ 18-16 DROP VIEW ........................................................................................................................................ 18-18 EXPLAIN PLAN .................................................................................................................................. 18-20 FLASHBACK DATABASE ................................................................................................................ 18-23 FLASHBACK TABLE ......................................................................................................................... 18-26 GRANT ................................................................................................................................................. 18-32 INSERT ................................................................................................................................................. 18-51 LOCK TABLE ...................................................................................................................................... 18-68 MERGE ................................................................................................................................................. 18-71 NOAUDIT ............................................................................................................................................ 18-76 PURGE .................................................................................................................................................. 18-80 RENAME .............................................................................................................................................. 18-82 REVOKE ............................................................................................................................................... 18-84 ROLLBACK ......................................................................................................................................... 18-92 19 SQL Statements: SAVEPOINT to UPDATE SAVEPOINT .......................................................................................................................................... 19-2 SELECT ................................................................................................................................................... 19-4 SET CONSTRAINT[S] ...................................................................................................................... 19-48 SET ROLE ............................................................................................................................................ 19-50 SET TRANSACTION ........................................................................................................................ 19-52 TRUNCATE ......................................................................................................................................... 19-55
- 19. xix UPDATE ............................................................................................................................................... 19-59 A How to Read Syntax Diagrams Graphic Syntax Diagrams...................................................................................................................... A-1 Required Keywords and Parameters ............................................................................................ A-2 Optional Keywords and Parameters ............................................................................................. A-3 Syntax Loops...................................................................................................................................... A-3 Multipart Diagrams ......................................................................................................................... A-4 Database Objects .............................................................................................................................. A-4 B Oracle and Standard SQL ANSI Standards ...................................................................................................................................... B-1 ISO Standards .......................................................................................................................................... B-2 Oracle Compliance To Core SQL:2003................................................................................................. B-3 Oracle Support for Optional Features of SQL/Foundation:2003.................................................... B-8 Oracle Compliance with SQL/CLI:2003 ............................................................................................ B-15 Oracle Compliance with SQL/PSM:2003 .......................................................................................... B-15 Oracle Compliance with SQL/MED:2003 ......................................................................................... B-15 Oracle Compliance with SQL/XML:2005.......................................................................................... B-16 Oracle Compliance with FIPS 127-2 ................................................................................................. B-22 Oracle Extensions to Standard SQL .................................................................................................. B-24 Character Set Support........................................................................................................................... B-24 C Oracle Regular Expression Support Multilingual Regular Expression Syntax .......................................................................................... C-1 Regular Expression Operator Multilingual Enhancements............................................................ C-2 Perl-influenced Extensions in Oracle Regular Expressions ........................................................... C-3 D Oracle Database Reserved Words E Examples Using Extensible Indexing ................................................................................................................... E-1 Using XML in SQL Statements ............................................................................................................ E-8 Index
- 20. xx
- 21. xxi Preface This reference contains a complete description of the Structured Query Language (SQL) used to manage information in an Oracle Database. Oracle SQL is a superset of the American National Standards Institute (ANSI) and the International Standards Organization (ISO) SQL:1999 standard. This Preface contains these topics: ■ Intended Audience ■ Documentation Accessibility ■ Related Documents ■ Conventions Intended Audience The Oracle Database SQL Reference is intended for all users of Oracle SQL. Documentation Accessibility Our goal is to make Oracle products, services, and supporting documentation accessible, with good usability, to the disabled community. To that end, our documentation includes features that make information available to users of assistive technology. This documentation is available in HTML format, and contains markup to facilitate access by the disabled community. Accessibility standards will continue to evolve over time, and Oracle is actively engaged with other market-leading technology vendors to address technical obstacles so that our documentation can be accessible to all of our customers. For more information, visit the Oracle Accessibility Program Web site at http://www.oracle.com/accessibility/ Accessibility of Code Examples in Documentation Screen readers may not always correctly read the code examples in this document. The conventions for writing code require that closing braces should appear on an otherwise empty line; however, some screen readers may not always read a line of text that consists solely of a bracket or brace. Accessibility of Links to External Web Sites in Documentation This documentation may contain links to Web sites of other companies or organizations that Oracle does not own or control. Oracle neither evaluates nor makes any representations regarding the accessibility of these Web sites.
- 22. xxii TTY Access to Oracle Support Services Oracle provides dedicated Text Telephone (TTY) access to Oracle Support Services within the United States of America 24 hours a day, seven days a week. For TTY support, call 800.446.2398. Related Documents For more information, see these Oracle resources: ■ Oracle Database PL/SQL User's Guide and Reference for information on PL/SQL, the procedural language extension to Oracle SQL ■ Pro*C/C++ Programmer's Guide, Oracle SQL*Module for Ada Programmer's Guide, and the Pro*COBOL Programmer's Guide for detailed descriptions of Oracle embedded SQL Many of the examples in this book use the sample schemas, which are installed by default when you select the Basic Installation option with an Oracle Database installation. Refer to Oracle Database Sample Schemas for information on how these schemas were created and how you can use them yourself. Conventions The following text conventions are used in this document: Convention Meaning boldface Boldface type indicates graphical user interface elements associated with an action, or terms defined in text or the glossary. italic Italic type indicates book titles, emphasis, or placeholder variables for which you supply particular values. monospace Monospace type indicates commands within a paragraph, URLs, code in examples, text that appears on the screen, or text that you enter.
- 23. xxiii What's New in the SQL Reference? This section describes new features of Oracle Database 10g and provides pointers to additional information. For information on features that were new in earlier versions of Oracle Database, please refer to the documentation for the earlier release. Oracle Database 10g Release 2 New Features in the SQL Reference The following top-level SQL statements are new or enhanced in this release: ■ ALTER DATABASE on page 10-9 has been enhanced as follows: – New syntax in the standby_database_clauses lets you bring a logical standby database to the same state as the primary database. – Additional new syntax in the standby_database_clauses lets you convert a primary database outside the Data Guard environment into a physical standby database. – New syntax in the managed_standby_recovery clause lets you create a logical standby database from the physical standby database. – New syntax in the database_file_clauses lets you rename tempfiles as well as datafiles and redo log files. ■ ALTER DISKGROUP on page 10-48 has new syntax that lets you specify when in the course of a diskgroup rebalance operation control should be returned to the user. ■ ALTER SYSTEM on page 11-60 has new syntax that lets you load information from the server wallet into memory for database access, and to generate a new transparent database encryption master key: ■ ALTER TABLESPACE on page 12-79 contains new syntax that lets you drop an empty datafile or tempfile from the data dictionary and remove it from the operating system. ■ ALTER USER on page 13-18 contains new syntax that lets you expose a user to proxy use by enterprise users. ■ COMMIT on page 13-59 contains a new WRITE clause that lets you specify the priority with which the redo information generated by the commit operation is written to the redo log. ■ CREATE DATABASE LINK on page 14-31 has new syntax that helps Data Pump provide an encoded password for the database link during import of data.
- 24. xxiv ■ CREATE DIMENSION on page 14-36 and ALTER DIMENSION on page 10-45 contain new syntax that lets you preserve the hierarchical chain of parent-child relationship by an alternative path that skips over a specified level if it is null. ■ CREATE RESTORE POINT on page 15-60 is a new SQL statement that lets you create a restore point, to which you can flash back a table or the database. ■ CREATE TABLE on page 16-6 documents the new limit on number of partitions and subpartitions as 1024K - 1. ■ CREATE TABLE on page 16-6 and ALTER TABLE on page 12-2 contains new syntax that lets you encrypt column data. ■ CREATE USER on page 17-26 and ALTER USER on page 13-18 contain new syntax for determining how global and external users are identified. ■ DROP RESTORE POINT on page 17-79 is a new SQL statement that lets you drop a restore point. ■ FLASHBACK DATABASE on page 18-23 has new syntax that lets you flash back the database to a restore point. ■ FLASHBACK TABLE on page 18-26 has new syntax that lets you flash back a table to a restore point. The following clauses are modified in this release: ■ All of the DML statements (INSERT, UPDATE, DELETE, MERGE) now have an error logging clause. See for example INSERT on page 18-51. ■ "Model Expressions" on page 6-11 have been enhanced to allow analytic functions and FOR loops. The following built-in data mining functions are new in this release: ■ CLUSTER_ID on page 5-29 ■ CLUSTER_PROBABILITY on page 5-30 ■ CLUSTER_SET on page 5-32 ■ FEATURE_ID on page 5-63 ■ FEATURE_SET on page 5-65 ■ FEATURE_VALUE on page 5-67 ■ PREDICTION on page 5-120 ■ PREDICTION_COST on page 5-122 ■ PREDICTION_DETAILS on page 5-123 ■ PREDICTION_PROBABILITY on page 5-124 ■ PREDICTION_SET on page 5-126 The following built-in XML functions are new in this release: ■ APPENDCHILDXML ■ DELETEXML ■ INSERTCHILDXML ■ INSERTXMLBEFORE ■ XMLCDATA ■ XMLCOMMENT
- 25. xxv ■ XMLPI ■ XMLROOT ■ XMLPARSE ■ XMLPI ■ XMLQUERY ■ XMLSERIALIZE ■ XMLTABLE The following datatypes are new in this release: ■ "SDO_TOPO_GEOMETRY" on page 2-35 The following pseudocolumns are new in this release: ■ COLUMN_VALUE Pseudocolumn on page 3-6 The following miscellaneous changes have been made: ■ Appendix C, "Oracle Regular Expression Support" on page C-1 lists the Perl-influenced operators that are now supported in Oracle regular expression functions and conditions. ■ Two new hints are provided to handle parallel join bitmap filtering: "PX_JOIN_ FILTER Hint" on page 2-93 and "NO_PX_JOIN_FILTER Hint" on page 2-88. ■ The new CHANGE NOTIFICATION system privilege is documented in GRANT on page 18-32. Oracle Database 10g Release 1 New Features in the SQL Reference The following datatypes are new in this release: ■ The binary floating-point datatypes BINARY_FLOAT on page 2-12 and BINARY_ DOUBLE on page 2-12 ■ The spatial datatype SDO_GEORASTER on page 2-35 ■ The interMedia datatype SI_StillImage on page 2-36 and six related Still Image object types The following top-level SQL statements are new or enhanced in this release: ■ A number of new top-level SQL statements have been added to support Automatic Storage Management: – CREATE DISKGROUP on page 14-44 – ALTER DISKGROUP on page 10-48 – DROP DISKGROUP on page 17-60 In addition, the following statements have added syntax in support of Automatic Storage Management: – file_specification subclauses, datafile_tempfile_spec and redo_log_ file_spec, let you specify Automatic Storage Management files in the form of ASM_filename on page 8-30, as well as file system files – CREATE CONTROLFILE on page 14-12 lets you specify Automatic Storage Management files as well as file system files
- 26. xxvi – CREATE TABLESPACE on page 16-61 lets you create a tablespace within an Automatic Storage Management disk group using the "DATAFILE | TEMPFILE Clause" on page 16-65 ■ CREATE DATABASE on page 14-18 has new syntax that lets you create a default permanent tablespace for the database. ■ ALTER DATABASE on page 10-9 has new syntax that lets you: – Specify multiple temporary tablespaces (a tablespace group) as the database default temporary tablespaces – Assign or reassign a tablespace as the database default permanent tablespace (using the DEFAULT TABLESPACE clause) – Reset the target recovery incarnation for the database from the current incarnation to the prior incarnation – Begin backup of all the datafiles in the database – Enable block change tracking for incremental backups of the database – Update both global and local partitioned indexes as part of table partition maintenance operations – Revert the entire database, or some tablespaces of the database, to an earlier version – Control the relationship between primary databases and logical and physical standby databases – Assign or reassign a tablespace as the default permanent tablespace for the database – Add a logfile or enable a redo log thread by specifying an instance name rather than a thread number ■ ALTER MATERIALIZED VIEW LOG on page 11-15: – Has a new FORCE clause that lets you specify the addition of attributes that the materialized view log already has without causing Oracle to return an error – Lets you instruct Oracle Database to record a sequence value in the materialized view log ■ ALTER SYSTEM on page 11-60 has new syntax that lets you flush the buffer cache of the system global area (SGA). ■ ALTER TABLE on page 12-2 has new syntax that lets you manually compact the table segment, adjust the high water mark, and free the recuperated space. ■ ALTER TYPE on page 13-5 has new syntax that lets you modify varrays and nested tables of scalar types. ■ ALTER TABLESPACE on page 12-79 has new syntax that lets you: – Rename the tablespace – Guarantee that unexpired undo data will be preserved, even at the expense of ongoing transactions that require undo segment space ■ CREATE DATABASE on page 14-18 has new syntax that lets you: – Specify datafiles for the new SYSAUX system tablespace
- 27. xxvii – Specify a bigfile tablespace as the default for the database and override the default for undo and default temporary tablespaces as well. A bigfile tablespace contains a single datafile that can be up to 4GB in size. – Create a default permanent tablespace for the database. ■ CREATE DIMENSION on page 14-36 and ALTER DIMENSION on page 10-45 have new syntax that lets you assign a name to a dimension attribute that is different from the level name. ■ CREATE INDEX on page 14-58 and ALTER INDEX on page 10-64 have new syntax that lets you create and maintain global hash-partitioned indexes. ■ CREATE INDEXTYPE on page 14-81 and ALTER INDEXTYPE on page 10-82 have new syntax that supports array inserts using the ODCIIndexInsert method. ■ CREATE MATERIALIZED VIEW on page 15-4 and ALTER MATERIALIZED VIEW on page 11-2 have new syntax that enhances refresh operations. ■ CREATE OPERATOR on page 15-32 and ALTER OPERATOR on page 11-21 have new syntax that lets you pass column information to the functional implementation of the operator. ■ CREATE TABLESPACE on page 16-61 has new syntax that lets you create a bigfile tablespace. Such a tablespace contains a single datafile that can contain up to 232 or 4G blocks, resulting in a datafile of up to 128 terabytes (TB). CREATE DATABASE on page 14-18 has related syntax that lets you specify a bigfile tablespace as the default, undo, and default temporary tablespace for the database. ■ CREATE TABLESPACE on page 16-61 and ALTER TABLESPACE on page 12-79 have new syntax that lets you assign or reassign a temporary tablespace to a tablespace group. ■ CREATE USER on page 17-26 and ALTER USER on page 13-18 have new syntax that lets you specify multiple temporary tablespaces (a tablespace group) to a user. ■ DROP TABLE on page 18-5 has a new PURGE clause that lets you drop the table without moving it to the recycle bin. ■ FLASHBACK DATABASE on page 18-23 is a new statement that lets you revert the entire database to an earlier version. ■ FLASHBACK TABLE on page 18-26 is a new statement that lets you revert one or more tables to an earlier system change number (SCN) or timestamp or retrieve a table that was dropped. ■ MERGE on page 18-71 has new syntax that lets you: – Specify either the update operation or the insert operation, or both – Delete rows from the target table during the update operation ■ PURGE on page 18-80 is a new SQL statement that lets you permanently remove previously dropped objects from the recycle bin and release the space that was associated with them. ■ SELECT on page 19-4 has new syntax that lets you: – Issue a versions query, which returns all incarnations of the rows returned by the query within a specified SCN or time range. – Perform a query on a partitioned outer join. The new syntax supports data densification, the process of querying sparse data along a particular
- 28. xxviii dimension of data and returning rows that otherwise would have been omitted from the data returned by the query. – View the results of a query as a multidimensional array and perform associated calculations. The following clauses are modified in this release: ■ In the physical_attributes_clause on page 8-42, the MAXTRANS parameter has been deprecated. ■ The name of the data_segment_compression clause has been changed to table_compression for semantic clarity. The functionality has not changed. This clause appears in a number of SQL statements. For example, see CREATE TABLE table_compression on page 16-26. The following built-in functions are new in this release: ■ A new aggregate function COLLECT on page 5-35. ■ A new category of collection functions lets you manipulate nested tables and varrays. The collection functions are: – CARDINALITY on page 5-24 – POWERMULTISET on page 5-118 – POWERMULTISET_BY_CARDINALITY on page 5-119 – SET on page 5-155 ■ A new category of model functions are for use in specialized calculations and are valid only in the model_clause of a query. The model functions are: – CV on page 5-49 – PRESENTNNV on page 5-128 – PRESENTV on page 5-129 – PREVIOUS on page 5-130 ■ Functions to manipulate binary floating-point numbers: – TO_BINARY_DOUBLE on page 5-188 – TO_BINARY_FLOAT on page 5-189 – NANVL on page 5-98 – REMAINDER on page 5-147 ■ ORA_HASH on page 5-112 ■ The regular expression functions REGEXP_INSTR on page 5-136, REGEXP_ REPLACE on page 5-138, and REGEXP_SUBSTR on page 5-140. The Oracle Database implementation of regular expression support is discussed in Appendix C, "Oracle Regular Expression Support". ■ A new set of aggregate functions to support statistical analysis of data: – Correlation functions CORR_* on page 5-39 – MEDIAN on page 5-94 – STATS_BINOMIAL_TEST – STATS_CROSSTAB – STATS_F_TEST
- 29. xxix – STATS_KS_TEST – STATS_MODE – STATS_MW_TEST – STATS_ONE_WAY_ANOVA – T-test functions STATS_T_TEST_* – STATS_WSR_TEST The following SQL operators are new or enhanced in this release: ■ Equality and inequality operators (= and <>) can be used to compare nested tables and varrays. ■ The hierarchical operator: CONNECT_BY_ROOT on page 4-5 ■ The multiset operators: MULTISET EXCEPT on page 4-6, MULTISET INTERSECT on page 4-7, and MULTISET UNION on page 4-8 The following pseudocolumns are new in this release: ■ The hierarchical pseudo columns: CONNECT_BY_ISLEAF Pseudocolumn on page 3-2 and CONNECT_BY_ISCYCLE Pseudocolumn on page 3-1 ■ The "Version Query Pseudocolumns" on page 3-5 let you extract information about the rows returned by a version query. ■ The pseudocolumn ORA_ROWSCN Pseudocolumn on page 3-8 lets you obtain the system change number of the most recent operation on a table. The following conditions are new in this release: ■ The [NOT] IN conditions, formerly referred to as "membership condition", are now documented as "IN conditions" to distinguish them from the new MEMBER conditions (see IN Condition on page 7-21) ■ The "Floating-Point Conditions" (IS [NOT] NAN and IS [NOT] INFINITE) on page 7-7 ■ IS A SET Condition on page 7-11 ■ IS ANY Condition on page 7-9 ■ IS EMPTY Condition on page 7-11 ■ IS PRESENT Condition on page 7-10 ■ MEMBER Condition on page 7-12 ■ REGEXP_LIKE Condition on page 7-17 ■ SUBMULTISET Condition on page 7-13 The following miscellaneous features are added: ■ New locale-independent format elements have been added to the tables in "Format Models" on page 2-54. ■ Oracle Database now performs implicit conversion between CLOB and NCLOB data. ■ You can now specify a LOB column in the UPDATE OF clause when creating an update DML trigger.
- 30. xxx
- 31. Introduction to Oracle SQL 1-1 1 Introduction to Oracle SQL Structured Query Language (SQL) is the set of statements with which all programs and users access data in an Oracle database. Application programs and Oracle tools often allow users access to the database without using SQL directly, but these applications in turn must use SQL when executing the user's request. This chapter provides background information on SQL as used by most database systems. This chapter contains these topics: ■ History of SQL ■ SQL Standards ■ Recent Enhancements ■ Lexical Conventions ■ Tools Support History of SQL Dr. E. F. Codd published the paper, "A Relational Model of Data for Large Shared Data Banks", in June 1970 in the Association of Computer Machinery (ACM) journal, Communications of the ACM. Codd's model is now accepted as the definitive model for relational database management systems (RDBMS). The language, Structured English Query Language (SEQUEL) was developed by IBM Corporation, Inc., to use Codd's model. SEQUEL later became SQL (still pronounced "sequel"). In 1979, Relational Software, Inc. (now Oracle) introduced the first commercially available implementation of SQL. Today, SQL is accepted as the standard RDBMS language. SQL Standards Oracle strives to comply with industry-accepted standards and participates actively in SQL standards committees. Industry-accepted committees are the American National Standards Institute (ANSI) and the International Organization for Standardization (ISO), which is affiliated with the International Electrotechnical Commission (IEC). Both ANSI and the ISO/IEC have accepted SQL as the standard language for relational databases. When a new SQL standard is simultaneously published by these organizations, the names of the standards conform to conventions used by the organization, but the standards are technically identical. The latest SQL standard was adopted in July 2003 and is often called SQL:2003. The formal names of this standard are: ■ ANSI/ISO/IEC 9075:2003, "Database Language SQL", Parts 1 ("SQL/Framework"), 2 ("SQL/Foundation"), 3 ("SQL/CLI"), 4 ("SQL/PSM"), 9
- 32. SQL Standards 1-2 Oracle Database SQL Reference ("SQL/MED"), 10 ("SQL/OLB"), 11 ("SQL/Schemata"), 13 ("SQL/JRT") and 14 ("SQL/XML") ■ ISO/IEC 9075:2003, "Database Language SQL", Parts 1 ("SQL/Framework"), 2 ("SQL/Foundation"), 3 ("SQL/CLI"), 4 ("SQL/PSM"), 9 ("SQL/MED"), 10 ("SQL/OLB"), 11 ("SQL/Schemata"), 13 ("SQL/JRT") and 14 ("SQL/XML") At this writing, the next edition of Part 14, SQL/XML (ISO/IEC 9075-14) is in the process of final approval as an International Standard, with adoption expected in the final quarter of 2005. How SQL Works The strengths of SQL provide benefits for all types of users, including application programmers, database administrators, managers, and end users. Technically speaking, SQL is a data sublanguage. The purpose of SQL is to provide an interface to a relational database such as Oracle Database, and all SQL statements are instructions to the database. In this SQL differs from general-purpose programming languages like C and BASIC. Among the features of SQL are the following: ■ It processes sets of data as groups rather than as individual units. ■ It provides automatic navigation to the data. ■ It uses statements that are complex and powerful individually, and that therefore stand alone. Flow-control statements were not part of SQL originally, but they are found in the recently accepted optional part of SQL, ISO/IEC 9075-5: 1996. Flow-control statements are commonly known as "persistent stored modules" (PSM), and the PL/SQL extension to Oracle SQL is similar to PSM. SQL lets you work with data at the logical level. You need to be concerned with the implementation details only when you want to manipulate the data. For example, to retrieve a set of rows from a table, you define a condition used to filter the rows. All rows satisfying the condition are retrieved in a single step and can be passed as a unit to the user, to another SQL statement, or to an application. You need not deal with the rows one by one, nor do you have to worry about how they are physically stored or retrieved. All SQL statements use the optimizer, a part of Oracle Database that determines the most efficient means of accessing the specified data. Oracle also provides techniques that you can use to make the optimizer perform its job better. SQL provides statements for a variety of tasks, including: ■ Querying data ■ Inserting, updating, and deleting rows in a table ■ Creating, replacing, altering, and dropping objects ■ Controlling access to the database and its objects ■ Guaranteeing database consistency and integrity SQL unifies all of the preceding tasks in one consistent language. See Also: Appendix B, "Oracle and Standard SQL" for a detailed description of Oracle Database conformance to the SQL:2003 standards
- 33. Lexical Conventions Introduction to Oracle SQL 1-3 Common Language for All Relational Databases All major relational database management systems support SQL, so you can transfer all skills you have gained with SQL from one database to another. In addition, all programs written in SQL are portable. They can often be moved from one database to another with very little modification. Recent Enhancements The Oracle Database SQL engine is the underpinning of all Oracle Database applications. Oracle SQL continually evolves to meet the growing demands of database applications and to support emerging computing architectures, APIs, and network protocols. In addition to traditional structured data, SQL is capable of storing, retrieving, and processing more complex data: ■ Object types, collection types, and REF types provide support for complex structured data. A number of standard-compliant multiset operators are now supported for the nested table collection type. ■ Large objects (LOBs) provide support for both character and binary unstructured data. A single LOB can reach a size of 8 to 128 terabytes, depending on database block size. ■ The XMLType datatype provides support for semistructured XML data. Native support of standards-based capabilities includes the following features: ■ Native regular expression support lets you perform pattern searches on and manipulate loosely formatted, free-form text within the database. ■ Native floating-point datatypes based on the IEEE754 standard improve the floating-point processing common in XML and Java standards and reduce the storage space required for numeric data. ■ Built-in SQL aggregate and analytic functions facilitate access to and manipulation of data in data warehouses and data marts. Ongoing enhancements in Oracle SQL will continue to provide comprehensive support for the development of versatile, scalable, high-performance database applications. Lexical Conventions The following lexical conventions for issuing SQL statements apply specifically to the Oracle Database implementation of SQL, but are generally acceptable in other SQL implementations. When you issue a SQL statement, you can include one or more tabs, carriage returns, spaces, or comments anywhere a space occurs within the definition of the statement. Thus, Oracle Database evaluates the following two statements in the same manner: SELECT last_name,salary*12,MONTHS_BETWEEN(hire_date, SYSDATE) FROM employees WHERE department_id = 30 ORDER BY last_name; SELECT last_name, salary * 12, MONTHS_BETWEEN( hire_date, SYSDATE )
- 34. Tools Support 1-4 Oracle Database SQL Reference FROM employees ORDER BY last_name; Case is insignificant in reserved words, keywords, identifiers and parameters. However, case is significant in text literals and quoted names. Please refer to "Text Literals" on page 2-45 for a syntax description of text literals. Tools Support Oracle provides a number of utilities to facilitate your SQL development process: ■ SQL*Plus is an interactive and batch query tool that is installed with every Oracle Database server or client installation. It has a command-line user interface and a web-based user interface called iSQL*Plus. ■ Oracle JDeveloper is a multiple-platform integrated development environment supporting the complete lifecycle of development for Java, Web services, and SQL. It provides a graphical interface for executing and tuning SQL statements and a visual schema diagrammer (database modeler). It also supports editing, compiling, and debugging PL/SQL applications. ■ Oracle HTML DB is a hosted environment for developing and deploying database-related Web applications. SQL Workshop is a component of Oracle HTML DB that lets you view and manage database objects from a Web browser. SQL Workshop offers quick access to a SQL command processor and a SQL script repository. The Oracle Call Interface and Oracle precompilers let you embed standard SQL statements within a procedure programming language. ■ The Oracle Call Interface (OCI) lets you embed SQL statements in C programs. ■ The Oracle precompilers, Pro*C/C++ and Pro*COBOL, interpret embedded SQL statements and translate them into statements that can be understood by C/C++ and COBOL compilers, respectively. Most (but not all) Oracle tools also support all features of Oracle SQL. This reference describes the complete functionality of SQL. If the Oracle tool that you are using does not support this complete functionality, then you can find a discussion of the restrictions in the manual describing the tool, such as SQL*Plus User's Guide and Reference. See Also: SQL*Plus User's Guide and Reference and Oracle HTML DB User's Guide for more information on these products See Also: Oracle C++ Call Interface Programmer's Guide, Pro*COBOL Programmer's Guide, and Oracle Call Interface Programmer's Guide for additional information on the embedded SQL statements allowed in each product
- 35. Basic Elements of Oracle SQL 2-1 2 Basic Elements of Oracle SQL This chapter contains reference information on the basic elements of Oracle SQL. These elements are the simplest building blocks of SQL statements. Therefore, before using the statements described in Chapter 10 through Chapter 19, you should familiarize yourself with the concepts covered in this chapter. This chapter contains these sections: ■ Datatypes ■ Literals ■ Format Models ■ Nulls ■ Comments ■ Database Objects ■ Schema Object Names and Qualifiers ■ Syntax for Schema Objects and Parts in SQL Statements Datatypes Each value manipulated by Oracle Database has a datatype. The datatype of a value associates a fixed set of properties with the value. These properties cause Oracle to treat values of one datatype differently from values of another. For example, you can add values of NUMBER datatype, but not values of RAW datatype. When you create a table or cluster, you must specify a datatype for each of its columns. When you create a procedure or stored function, you must specify a datatype for each of its arguments. These datatypes define the domain of values that each column can contain or each argument can have. For example, DATE columns cannot accept the value February 29 (except for a leap year) or the values 2 or 'SHOE'. Each value subsequently placed in a column assumes the datatype of the column. For example, if you insert '01-JAN-98' into a DATE column, then Oracle treats the '01-JAN-98' character string as a DATE value after verifying that it translates to a valid date. Oracle Database provides a number of built-in datatypes as well as several categories for user-defined types that can be used as datatypes. The syntax of Oracle datatypes appears in the diagrams that follow. The text of this section is divided into the following sections: ■ Oracle Built-in Datatypes ■ ANSI, DB2, and SQL/DS Datatypes
- 36. Datatypes 2-2 Oracle Database SQL Reference ■ User-Defined Types ■ Oracle-Supplied Types ■ Datatype Comparison Rules ■ Data Conversion A datatype is either scalar or nonscalar. A scalar type contains an atomic value, whereas a nonscalar (sometimes called a "collection") contains a set of values. A large object (LOB) is a special form of scalar datatype representing a large scalar value of binary or character data. LOBs are subject to some restrictions that do not affect other scalar types because of their size. Those restrictions are documented in the context of the relevant SQL syntax. The Oracle precompilers recognize other datatypes in embedded SQL programs. These datatypes are called external datatypes and are associated with host variables. Do not confuse built-in datatypes and user-defined types with external datatypes. For information on external datatypes, including how Oracle converts between them and built-in datatypes or user-defined types, see Pro*COBOL Programmer's Guide, and Pro*C/C++ Programmer's Guide. datatypes::= Oracle_built_in_datatypes::= For descriptions of the Oracle built-in datatypes, please refer to "Oracle Built-in Datatypes" on page 2-6. Oracle_built_in_datatypes ANSI_supported_datatypes user_defined_types Oracle_supplied_types character_datatypes number_datatypes long_and_raw_datatypes datetime_datatypes large_object_datatypes rowid_datatypes
- 37. Datatypes Basic Elements of Oracle SQL 2-3 character_datatypes::= number_datatypes::= long_and_raw_datatypes::= datetime_datatypes::= large_object_datatypes::= CHAR ( size BYTE CHAR ) VARCHAR2 ( size BYTE CHAR ) NCHAR ( size ) NVARCHAR2 ( size ) NUMBER ( precision , scale ) BINARY_FLOAT BINARY_DOUBLE LONG LONG RAW RAW ( size ) DATE TIMESTAMP ( fractional_seconds_precision ) WITH LOCAL TIME ZONE INTERVAL YEAR ( year_precision ) TO MONTH INTERVAL DAY ( day_precision ) TO SECOND ( fractional_seconds_precision ) BLOB CLOB NCLOB BFILE
- 38. Datatypes 2-4 Oracle Database SQL Reference rowid_datatypes::= The ANSI-supported datatypes appear in the figure that follows. "ANSI, DB2, and SQL/DS Datatypes" on page 2-29 discusses the mapping of ANSI-supported datatypes to Oracle built-in datatypes. ANSI_supported_datatypes::= Oracle_supplied_types::= For a description of the expression_filter_type, please refer to "Expression Filter Type" on page 2-37. Other Oracle-supplied types follow: ROWID UROWID ( size ) CHARACTER VARYING ( size ) CHAR NCHAR VARYING ( size ) VARCHAR ( size ) NATIONAL CHARACTER CHAR VARYING ( size ) NUMERIC DECIMAL DEC ( precision , scale ) INTEGER INT SMALLINT FLOAT ( size ) DOUBLE PRECISION REAL any_types XML_types spatial_types media_types expression_filter_type
- 39. Datatypes Basic Elements of Oracle SQL 2-5 any_types::= For descriptions of the Any types, please refer to "Any Types" on page 2-32. XML_types::= For descriptions of the XML types, please refer to "XML Types" on page 2-33. spatial_types::= For descriptions of the spatial types, please refer to "Spatial Types" on page 2-34. media_types::= still_image_object_types::= For descriptions of the media types, please refer to "Media Types" on page 2-35. SYS.AnyData SYS.AnyType SYS.AnyDataSet XMLType URIType SDO_Geometry SDO_Topo_Geometry SDO_GeoRaster ORDAudio ORDImage ORDVideo ORDDoc OrdImageSignature still_image_object_types SI_StillImage SI_AverageColor SI_PositionalColor SI_ColorHistogram SI_Texture SI_FeatureList SI_Color
- 40. Datatypes 2-6 Oracle Database SQL Reference Oracle Built-in Datatypes The table that follows summarizes Oracle built-in datatypes. Please refer to the syntax in the preceding sections for the syntactic elements. The codes listed for the datatypes are used internally by Oracle Database. The datatype code of a column or object attribute is returned by the DUMP function. Table 2–1 Built-in Datatype Summary Code Datatype Description 1 VARCHAR2(size [BYTE | CHAR]) Variable-length character string having maximum length size bytes or characters. Maximum size is 4000 bytes or characters, and minimum is 1 byte or 1 character. You must specify size for VARCHAR2. BYTE indicates that the column will have byte length semantics; CHAR indicates that the column will have character semantics. 1 NVARCHAR2(size) Variable-length Unicode character string having maximum length size characters. The number of bytes can be up to two times size for AL16UTF16 encoding and three times size for UTF8 encoding. Maximum size is determined by the national character set definition, with an upper limit of 4000 bytes. You must specify size for NVARCHAR2. 2 NUMBER[(precision [, scale]]) Number having precision p and scale s. The precision p can range from 1 to 38. The scale s can range from -84 to 127. 8 LONG Character data of variable length up to 2 gigabytes, or 231 -1 bytes. Provided for backward compatibility. 12 DATE Valid date range from January 1, 4712 BC to December 31, 9999 AD. The default format is determined explicitly by the NLS_ DATE_FORMAT parameter or implicitly by the NLS_TERRITORY parameter. The size is fixed at 7 bytes. This datatype contains the datetime fields YEAR, MONTH, DAY, HOUR, MINUTE, and SECOND. It does not have fractional seconds or a time zone. 21 BINARY_FLOAT 32-bit floating point number. This datatype requires 5 bytes, including the length byte. 22 BINARY_DOUBLE 64-bit floating point number. This datatype requires 9 bytes, including the length byte. 180 TIMESTAMP [(fractional_ seconds)] Year, month, and day values of date, as well as hour, minute, and second values of time, where fractional_seconds_ precision is the number of digits in the fractional part of the SECOND datetime field. Accepted values of fractional_ seconds_precision are 0 to 9. The default is 6. The default format is determined explicitly by the NLS_DATE_FORMAT parameter or implicitly by the NLS_TERRITORY parameter. The sizes varies from 7 to 11 bytes, depending on the precision. This datatype contains the datetime fields YEAR, MONTH, DAY, HOUR, MINUTE, and SECOND. It contains fractional seconds but does not have a time zone. 181 TIMESTAMP [(fractional_ seconds)] WITH TIME ZONE All values of TIMESTAMP as well as time zone displacement value, where fractional_seconds_precision is the number of digits in the fractional part of the SECOND datetime field. Accepted values are 0 to 9. The default is 6. The default format is determined explicitly by the NLS_DATE_FORMAT parameter or implicitly by the NLS_TERRITORY parameter. The size is fixed at 13 bytes. This datatype contains the datetime fields YEAR, MONTH, DAY, HOUR, MINUTE, SECOND, TIMEZONE_ HOUR, and TIMEZONE_MINUTE. It has fractional seconds and an explicit time zone.
- 41. Datatypes Basic Elements of Oracle SQL 2-7 231 TIMESTAMP [(fractional_ seconds)] WITH LOCAL TIME ZONE All values of TIMESTAMP WITH TIME ZONE, with the following exceptions: ■ Data is normalized to the database time zone when it is stored in the database. ■ When the data is retrieved, users see the data in the session time zone. The default format is determined explicitly by the NLS_DATE_ FORMAT parameter or implicitly by the NLS_TERRITORY parameter. The sizes varies from 7 to 11 bytes, depending on the precision. 182 INTERVAL YEAR [(year_ precision)] TO MONTH Stores a period of time in years and months, where year_ precision is the number of digits in the YEAR datetime field. Accepted values are 0 to 9. The default is 2. The size is fixed at 5 bytes. 183 INTERVAL DAY [(day_precision)] TO SECOND [(fractional_ seconds)] Stores a period of time in days, hours, minutes, and seconds, where ■ day_precision is the maximum number of digits in the DAY datetime field. Accepted values are 0 to 9. The default is 2. ■ fractional_seconds_precision is the number of digits in the fractional part of the SECOND field. Accepted values are 0 to 9. The default is 6. The size is fixed at 11 bytes. 23 RAW(size) Raw binary data of length size bytes. Maximum size is 2000 bytes. You must specify size for a RAW value. 24 LONG RAW Raw binary data of variable length up to 2 gigabytes. 69 ROWID Base 64 string representing the unique address of a row in its table. This datatype is primarily for values returned by the ROWID pseudocolumn. 208 UROWID [(size)] Base 64 string representing the logical address of a row of an index-organized table. The optional size is the size of a column of type UROWID. The maximum size and default is 4000 bytes. 96 CHAR [(size [BYTE | CHAR])] Fixed-length character data of length size bytes. Maximum size is 2000 bytes or characters. Default and minimum size is 1 byte. BYTE and CHAR have the same semantics as for VARCHAR2. 96 NCHAR[(size)] Fixed-length character data of length size characters. The number of bytes can be up to two times size for AL16UTF16 encoding and three times size for UTF8 encoding. Maximum size is determined by the national character set definition, with an upper limit of 2000 bytes. Default and minimum size is 1 character. 112 CLOB A character large object containing single-byte or multibyte characters. Both fixed-width and variable-width character sets are supported, both using the database character set. Maximum size is (4 gigabytes - 1) * (database block size). Table 2–1 (Cont.) Built-in Datatype Summary Code Datatype Description
- 42. Datatypes 2-8 Oracle Database SQL Reference The sections that follow describe the Oracle datatypes as they are stored in Oracle Database. For information on specifying these datatypes as literals, please refer to "Literals" on page 2-44. Character Datatypes Character datatypes store character (alphanumeric) data, which are words and free-form text, in the database character set or national character set. They are less restrictive than other datatypes and consequently have fewer properties. For example, character columns can store all alphanumeric values, but NUMBER columns can store only numeric values. Character data is stored in strings with byte values corresponding to one of the character sets, such as 7-bit ASCII or EBCDIC, specified when the database was created. Oracle Database supports both single-byte and multibyte character sets. These datatypes are used for character data: ■ CHAR Datatype ■ NCHAR Datatype ■ NVARCHAR2 Datatype ■ VARCHAR2 Datatype For information on specifying character datatypes as literals, please refer to "Text Literals" on page 2-45. CHAR Datatype The CHAR datatype specifies a fixed-length character string. Oracle ensures that all values stored in a CHAR column have the length specified by size. If you insert a value that is shorter than the column length, then Oracle blank-pads the value to column length. If you try to insert a value that is too long for the column, then Oracle returns an error. The default length for a CHAR column is 1 byte and the maximum allowed is 2000 bytes. A 1-byte string can be inserted into a CHAR(10) column, but the string is blank-padded to 10 bytes before it is stored. When you create a table with a CHAR column, by default you supply the column length in bytes. The BYTE qualifier is the same as the default. If you use the CHAR qualifier, for example CHAR(10 CHAR), then you supply the column length in characters. A character is technically a code point of the database character set. Its size can range from 1 byte to 4 bytes, depending on the database character set. The BYTE and CHAR qualifiers override the semantics specified by the NLS_LENGTH_ 112 NCLOB A character large object containing Unicode characters. Both fixed-width and variable-width character sets are supported, both using the database national character set. Maximum size is (4 gigabytes - 1) * (database block size). Stores national character set data. 113 BLOB A binary large object. Maximum size is (4 gigabytes - 1) * (database block size). 114 BFILE Contains a locator to a large binary file stored outside the database. Enables byte stream I/O access to external LOBs residing on the database server. Maximum size is 4 gigabytes. Table 2–1 (Cont.) Built-in Datatype Summary Code Datatype Description
- 43. Datatypes Basic Elements of Oracle SQL 2-9 SEMANTICS parameter, which has a default of byte semantics. For performance reasons, Oracle recommends that you use the NLS_LENGTH_SEMANTICS parameter to set length semantics and that you use the BYTE and CHAR qualifiers only when necessary to override the parameter. To ensure proper data conversion between databases with different character sets, you must ensure that CHAR data consists of well-formed strings. See Oracle Database Globalization Support Guide for more information on character set support. NCHAR Datatype The NCHAR datatype is a Unicode-only datatype. When you create a table with an NCHAR column, you define the column length in characters. You define the national character set when you create your database. The maximum length of a column is determined by the national character set definition. Width specifications of character datatype NCHAR refer to the number of characters. The maximum column size allowed is 2000 bytes. If you insert a value that is shorter than the column length, then Oracle blank-pads the value to column length. You cannot insert a CHAR value into an NCHAR column, nor can you insert an NCHAR value into a CHAR column. The following example compares the translated_description column of the pm.product_descriptions table with a national character set string: SELECT translated_description FROM product_descriptions WHERE translated_name = N'LCD Monitor 11/PM'; Please refer to Oracle Database Globalization Support Guide for information on Unicode datatype support. NVARCHAR2 Datatype The NVARCHAR2 datatype is a Unicode-only datatype. When you create a table with an NVARCHAR2 column, you supply the maximum number of characters it can hold. Oracle subsequently stores each value in the column exactly as you specify it, provided the value does not exceed the maximum length of the column. The maximum length of the column is determined by the national character set definition. Width specifications of character datatype NVARCHAR2 refer to the number of characters. The maximum column size allowed is 4000 bytes. Please refer to Oracle Database Globalization Support Guide for information on Unicode datatype support. VARCHAR2 Datatype The VARCHAR2 datatype specifies a variable-length character string. When you create a VARCHAR2 column, you supply the maximum number of bytes or characters of data that it can hold. Oracle subsequently stores each value in the column exactly as you specify it, provided the value does not exceed the column's maximum length of the column. If you try to insert a value that exceeds the specified length, then Oracle returns an error. You must specify a maximum length for a VARCHAR2 column. This maximum must be at least 1 byte, although the actual string stored is permitted to be a zero-length string (''). You can use the CHAR qualifier, for example VARCHAR2(10 CHAR), to give the maximum length in characters instead of bytes. A character is technically a code point of the database character set. CHAR and BYTE qualifiers override the setting of the See Also: "Datatype Comparison Rules" on page 2-37 for information on comparison semantics
- 44. Datatypes 2-10 Oracle Database SQL Reference NLS_LENGTH_SEMANTICS parameter, which has a default of bytes. For performance reasons, Oracle recommends that you use the NLS_LENGTH_SEMANTICS parameter to set length semantics and that you use the BYTE and CHAR qualifiers only when necessary to override the parameter. The maximum length of VARCHAR2 data is 4000 bytes. Oracle compares VARCHAR2 values using nonpadded comparison semantics. To ensure proper data conversion between databases with different character sets, you must ensure that VARCHAR2 data consists of well-formed strings. See Oracle Database Globalization Support Guide for more information on character set support. VARCHAR Datatype Do not use the VARCHAR datatype. Use the VARCHAR2 datatype instead. Although the VARCHAR datatype is currently synonymous with VARCHAR2, the VARCHAR datatype is scheduled to be redefined as a separate datatype used for variable-length character strings compared with different comparison semantics. Numeric Datatypes The Oracle Database numeric datatypes store positive and negative fixed and floating-point numbers, zero, infinity, and values that are the undefined result of an operation (that is, is "not a number" or NAN). For information on specifying numeric datatypes as literals, please refer to "Numeric Literals" on page 2-46. NUMBER Datatype The NUMBER datatype stores zero as well as positive and negative fixed numbers with absolute values from 1.0 x 10-130 to (but not including) 1.0 x 10126 . If you specify an arithmetic expression whose value has an absolute value greater than or equal to 1.0 x 10126 , then Oracle returns an error. Each NUMBER value requires from 1 to 22 bytes. Specify a fixed-point number using the following form: NUMBER(p,s) where: ■ p is the precision, or the total number of significant decimal digits, where the most significant digit is the left-most nonzero digit, and the least significant digit is the right-most known digit. Oracle guarantees the portability of numbers with precision of up to 20 base-100 digits, which is equivalent to 39 or 40 decimal digits depending on the position of the decimal point. ■ s is the scale, or the number of digits from the decimal point to the least significant digit. The scale can range from -84 to 127. – Positive scale is the number of significant digits to the right of the decimal point to and including the least significant digit. – Negative scale is the number of significant digits to the left of the decimal point, to but not including the least significant digit. For negative scale the least significant digit is on the left side of the decimal point, because the actual data is rounded to the specified number of places to the left of the decimal point. For example, a specification of (10,-2) means to round to hundreds. Scale can be greater than precision, most commonly when e notation is used. When scale is greater than precision, the precision specifies the maximum number of significant digits to the right of the decimal point. For example, a column defined as See Also: "Datatype Comparison Rules" on page 2-37 for information on comparison semantics
- 45. Datatypes Basic Elements of Oracle SQL 2-11 NUMBER(4,5) requires a zero for the first digit after the decimal point and rounds all values past the fifth digit after the decimal point. It is good practice to specify the scale and precision of a fixed-point number column for extra integrity checking on input. Specifying scale and precision does not force all values to a fixed length. If a value exceeds the precision, then Oracle returns an error. If a value exceeds the scale, then Oracle rounds it. Specify an integer using the following form: NUMBER(p) This represents a fixed-point number with precision p and scale 0 and is equivalent to NUMBER(p,0). Specify a floating-point number using the following form: NUMBER The absence of precision and scale designators specifies the maximum range and precision for an Oracle number. Table 2–2 show how Oracle stores data using different precisions and scales. Floating-Point Numbers Floating-point numbers can have a decimal point anywhere from the first to the last digit or can have no decimal point at all. An exponent may optionally be used following the number to increase the range (for example, 1.777 e-20 ). A scale value is not applicable to floating-point numbers, because the number of digits that can appear after the decimal point is not restricted. Binary floating-point numbers differ from NUMBER in the way the values are stored internally by Oracle Database. Values are stored using decimal precision for NUMBER. See Also: "Floating-Point Numbers" on page 2-11 Table 2–2 Storage of Scale and Precision Actual Data Specified As Stored As 123.89 NUMBER 123.89 123.89 NUMBER(3) 124 123.89 NUMBER(6,2) 123.89 123.89 NUMBER(6,1) 123.9 123.89 NUMBER(3) exceeds precision 123.89 NUMBER(4,2) exceeds precision 123.89 NUMBER(6,-2) 100 .01234 NUMBER(4,5) .01234 .00012 NUMBER(4,5) .00012 .000127 NUMBER(4,5) .00013 .0000012 NUMBER(2,7) .0000012 .00000123 NUMBER(2,7) .0000012 1.2e-4 NUMBER(2,5) 0.00012 1.2e-5 NUMBER(2,5) 0.00001
- 46. Datatypes 2-12 Oracle Database SQL Reference All literals that are within the range and precision supported by NUMBER are stored exactly as NUMBER. Literals are stored exactly because literals are expressed using decimal precision (the digits 0 through 9). Binary floating-point numbers are stored using binary precision (the digits 0 and 1). Such a storage scheme cannot represent all values using decimal precision exactly. Frequently, the error that occurs when converting a value from decimal to binary precision is undone when the value is converted back from binary to decimal precision. The literal 0.1 is such an example. Oracle Database provides two numeric datatypes exclusively for floating-point numbers: BINARY_FLOAT BINARY_FLOAT is a 32-bit, single-precision floating-point number datatype. Each BINARY_FLOAT value requires 5 bytes, including a length byte. BINARY_DOUBLE BINARY_DOUBLE is a 64-bit, double-precision floating-point number datatype. Each BINARY_DOUBLE value requires 9 bytes, including a length byte. In a NUMBER column, floating point numbers have decimal precision. In a BINARY_ FLOAT or BINARY_DOUBLE column, floating-point numbers have binary precision. The binary floating-point numbers support the special values infinity and NaN (not a number). You can specify floating-point numbers within the limits listed in Table 2–3 on page 2-12. The format for specifying floating-point numbers is defined in "Numeric Literals" on page 2-46. Oracle Database also supports the ANSI datatype FLOAT. You can specify this datatype using one of these syntactic forms: FLOAT FLOAT(n) The number n indicates the number of bits of precision that the value can store. The value for n can range from 1 to 126. To convert from binary to decimal precision, multiply n by 0.30103. To convert from decimal to binary precision, multiply the decimal precision by 3.32193. The maximum of 126 digits of binary precision is roughly equivalent to 38 digits of decimal precision. IEEE754 Conformance The Oracle implementation of floating-point datatypes conforms substantially with the Institute of Electrical and Electronics Engineers (IEEE) Standard for Binary Floating-Point Arithmetic, IEEE Standard 754-1985 (IEEE754). The new datatypes conform to IEEE754 in the following areas: ■ The SQL function SQRT implements square root. See SQRT on page 5-158. ■ The SQL function REMAINDER implements remainder. See REMAINDER on page 5-147. ■ Arithmetic operators conform. See "Arithmetic Operators" on page 4-3. ■ Comparison operators conform, except for comparisons with NaN. Oracle orders NaN greatest with respect to all other values, and evaluates NaN equal to NaN. See "Floating-Point Conditions" on page 7-7. Table 2–3 Floating Point Number Limits Value Binary-Float Binary-Double Maximum positive finite value 3.40282E+38F 1.79769313486231E+308 Minimum positive finite value 1.17549E-38F 2.22507485850720E-308
- 47. Datatypes Basic Elements of Oracle SQL 2-13 ■ Conversion operators conform. See "Conversion Functions" on page 5-5. ■ The default rounding mode is supported. ■ The default exception handling mode is supported. ■ The special values INF, -INF, and NaN are supported. See "Floating-Point Conditions" on page 7-7. ■ Rounding of BINARY_FLOAT and BINARY_DOUBLE values to integer-valued BINARY_FLOAT and BINARY_DOUBLE values is provided by the SQL functions ROUND, TRUNC, CEIL, and FLOOR. ■ Rounding of BINARY_FLOAT/BINARY_DOUBLE to decimal and decimal to BINARY_FLOAT/BINARY_DOUBLE is provided by the SQL functions TO_CHAR, TO_NUMBER, TO_NCHAR, TO_BINARY_FLOAT, TO_BINARY_DOUBLE, and CAST. The new datatypes do not conform to IEEE754 in the following areas: ■ -0 is coerced to +0. ■ Comparison with NaN is not supported. ■ All NaN values are coerced to either BINARY_FLOAT_NAN or BINARY_DOUBLE_ NAN. ■ Non-default rounding modes are not supported. ■ Non-default exception handling mode are not supported. Numeric Precedence Numeric precedence determines, for operations that support numeric datatypes, the datatype Oracle uses if the arguments to the operation have different datatypes. BINARY_DOUBLE has the highest numeric precedence, followed by BINARY_FLOAT, and finally by NUMBER. Therefore, in any operation on multiple numeric values: ■ If any of the operands is BINARY_DOUBLE, then Oracle attempts to convert all the operands implicitly to BINARY_DOUBLE before performing the operation. ■ If none of the operands is BINARY_DOUBLE but any of the operands is BINARY_ FLOAT, then Oracle attempts to convert all the operands implicitly to BINARY_ FLOAT before performing the operation. ■ Otherwise, Oracle attempts to convert all the operands to NUMBER before performing the operation. If any implicit conversion is needed and fails, then the operation fails. Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion. In the context of other datatypes, numeric datatypes have lower precedence than the datetime/interval datatypes and higher precedence than character and all other datatypes. LONG Datatype LONG columns store variable-length character strings containing up to 2 gigabytes -1, or 231 -1 bytes. LONG columns have many of the characteristics of VARCHAR2 columns. You can use LONG columns to store long text strings. The length of LONG values may be limited by the memory available on your computer. LONG literals are formed as described for "Text Literals" on page 2-45. Do not create tables with LONG columns. Use LOB columns (CLOB, NCLOB, BLOB) instead. LONG columns are supported only for backward compatibility.
- 48. Datatypes 2-14 Oracle Database SQL Reference Oracle also recommends that you convert existing LONG columns to LOB columns. LOB columns are subject to far fewer restrictions than LONG columns. Further, LOB functionality is enhanced in every release, whereas LONG functionality has been static for several releases. See the modify_col_properties clause of ALTER TABLE on page 12-2 and TO_LOB on page 5-196 for more information on converting LONG columns to LOB. You can reference LONG columns in SQL statements in these places: ■ SELECT lists ■ SET clauses of UPDATE statements ■ VALUES clauses of INSERT statements The use of LONG values is subject to these restrictions: ■ A table can contain only one LONG column. ■ You cannot create an object type with a LONG attribute. ■ LONG columns cannot appear in WHERE clauses or in integrity constraints (except that they can appear in NULL and NOT NULL constraints). ■ LONG columns cannot be indexed. ■ LONG data cannot be specified in regular expressions. ■ A stored function cannot return a LONG value. ■ You can declare a variable or argument of a PL/SQL program unit using the LONG datatype. However, you cannot then call the program unit from SQL. ■ Within a single SQL statement, all LONG columns, updated tables, and locked tables must be located on the same database. ■ LONG and LONG RAW columns cannot be used in distributed SQL statements and cannot be replicated. ■ If a table has both LONG and LOB columns, then you cannot bind more than 4000 bytes of data to both the LONG and LOB columns in the same SQL statement. However, you can bind more than 4000 bytes of data to either the LONG or the LOB column. In addition, LONG columns cannot appear in these parts of SQL statements: ■ GROUP BY clauses, ORDER BY clauses, or CONNECT BY clauses or with the DISTINCT operator in SELECT statements ■ The UNIQUE operator of a SELECT statement ■ The column list of a CREATE CLUSTER statement ■ The CLUSTER clause of a CREATE MATERIALIZED VIEW statement ■ SQL built-in functions, expressions, or conditions ■ SELECT lists of queries containing GROUP BY clauses ■ SELECT lists of subqueries or queries combined by the UNION, INTERSECT, or MINUS set operators ■ SELECT lists of CREATE TABLE ... AS SELECT statements ■ ALTER TABLE ... MOVE statements ■ SELECT lists in subqueries in INSERT statements Triggers can use the LONG datatype in the following manner:
- 49. Datatypes Basic Elements of Oracle SQL 2-15 ■ A SQL statement within a trigger can insert data into a LONG column. ■ If data from a LONG column can be converted to a constrained datatype (such as CHAR and VARCHAR2), then a LONG column can be referenced in a SQL statement within a trigger. ■ Variables in triggers cannot be declared using the LONG datatype. ■ :NEW and :OLD cannot be used with LONG columns. You can use Oracle Call Interface functions to retrieve a portion of a LONG value from the database. Datetime and Interval Datatypes The datetime datatypes are DATE, TIMESTAMP, TIMESTAMP WITH TIME ZONE, and TIMESTAMP WITH LOCAL TIME ZONE. Values of datetime datatypes are sometimes called datetimes. The interval datatypes are INTERVAL YEAR TO MONTH and INTERVAL DAY TO SECOND. Values of interval datatypes are sometimes called intervals. For information on expressing datetime and interval values as literals, please refer to "Datetime Literals" on page 2-49 and "Interval Literals" on page 2-51. Both datetimes and intervals are made up of fields. The values of these fields determine the value of the datatype. Table 2–4 lists the datetime fields and their possible values for datetimes and intervals. To avoid unexpected results in your DML operations on datetime data, you can verify the database and session time zones by querying the built-in SQL functions DBTIMEZONE and SESSIONTIMEZONE. If the time zones have not been set manually, Oracle Database uses the operating system time zone by default. If the operating system time zone is not a valid Oracle time zone, then Oracle uses UTC as the default value. See Also: Oracle Call Interface Programmer's Guide Table 2–4 Datetime Fields and Values Datetime Field Valid Values for Datetime Valid Values for INTERVAL YEAR -4712 to 9999 (excluding year 0) Any positive or negative integer MONTH 01 to 12 0 to 11 DAY 01 to 31 (limited by the values of MONTH and YEAR, according to the rules of the current NLS calendar parameter) Any positive or negative integer HOUR 00 to 23 0 to 23 MINUTE 00 to 59 0 to 59 SECOND 00 to 59.9(n), where 9(n) is the precision of time fractional seconds. The 9(n) portion is not applicable for DATE. 0 to 59.9(n), where 9(n) is the precision of interval fractional seconds TIMEZONE_HOUR -12 to 14 (This range accommodates daylight saving time changes.) Not applicable for DATE or TIMESTAMP. Not applicable
- 50. Datatypes 2-16 Oracle Database SQL Reference Note: TIMEZONE_HOUR and TIMEZONE_MINUTE are specified together and interpreted as an entity in the format +|- hh:mm, with values ranging from -12:59 to +14:00. Please refer to Oracle Data Provider for .NET Developer's Guide for information on specifying time zone values for that API. DATE Datatype The DATE datatype stores date and time information. Although date and time information can be represented in both character and number datatypes, the DATE datatype has special associated properties. For each DATE value, Oracle stores the following information: century, year, month, date, hour, minute, and second. You can specify a DATE value as a literal, or you can convert a character or numeric value to a date value with the TO_DATE function. For examples of expressing DATE values in both these ways, please refer to "Datetime Literals" on page 2-49. Using Julian Days A Julian day number is the number of days since January 1, 4712 BC. Julian days allow continuous dating from a common reference. You can use the date format model "J" with date functions TO_DATE and TO_CHAR to convert between Oracle DATE values and their Julian equivalents. The default date values are determined as follows: ■ The year is the current year, as returned by SYSDATE. ■ The month is the current month, as returned by SYSDATE. ■ The day is 01 (the first day of the month). ■ The hour, minute, and second are all 0. These default values are used in a query that requests date values where the date itself is not specified, as in the following example, which is issued in the month of May: SELECT TO_DATE(’2005’, ’YYYY’) FROM DUAL; TIMEZONE_MINUTE (See note at end of table) 00 to 59. Not applicable for DATE or TIMESTAMP. Not applicable TIMEZONE_REGION Query the TZNAME column of the V$TIMEZONE_ NAMES data dictionary view. Not applicable for DATE or TIMESTAMP. For a complete listing of all timezone regions, refer to Oracle Database Globalization Support Guide. Not applicable TIMEZONE_ABBR Query the TZABBREV column of the V$TIMEZONE_ NAMES data dictionary view. Not applicable for DATE or TIMESTAMP. Not applicable Note: Oracle Database uses the astronomical system of calculating Julian days, in which the year 4713 BC is specified as -4712. The historical system of calculating Julian days, in contrast, specifies 4713 BC as -4713. If you are comparing Oracle Julian days with values calculated using the historical system, then take care to allow for the 365-day difference in BC dates. For more information, see http://aa.usno.navy.mil/faq/docs/millennium.html. Table 2–4 (Cont.) Datetime Fields and Values Datetime Field Valid Values for Datetime Valid Values for INTERVAL
- 51. Datatypes Basic Elements of Oracle SQL 2-17 TO_DATE(' --------- 01-MAY-05 Example This statement returns the Julian equivalent of January 1, 1997: SELECT TO_CHAR(TO_DATE('01-01-1997', 'MM-DD-YYYY'),'J') FROM DUAL; TO_CHAR -------- 2450450 TIMESTAMP Datatype The TIMESTAMP datatype is an extension of the DATE datatype. It stores the year, month, and day of the DATE datatype, plus hour, minute, and second values. This datatype is useful for storing precise time values. Specify the TIMESTAMP datatype as follows: TIMESTAMP [(fractional_seconds_precision)] where fractional_seconds_precision optionally specifies the number of digits Oracle stores in the fractional part of the SECOND datetime field. When you create a column of this datatype, the value can be a number in the range 0 to 9. The default is 6. TIMESTAMP WITH TIME ZONE Datatype TIMESTAMP WITH TIME ZONE is a variant of TIMESTAMP that includes a time zone offset in its value. The time zone offset is the difference (in hours and minutes) between local time and UTC (Coordinated Universal Time—formerly Greenwich Mean Time). This datatype is useful for collecting and evaluating date information across geographic regions. Specify the TIMESTAMP WITH TIME ZONE datatype as follows: TIMESTAMP [(fractional_seconds_precision)] WITH TIME ZONE where fractional_seconds_precision optionally specifies the number of digits Oracle stores in the fractional part of the SECOND datetime field. When you create a column of this datatype, the value can be a number in the range 0 to 9. The default is 6. Oracle time zone data is derived from the public domain information available at ftp://elsie.nci.nih.gov/pub/. Oracle time zone data may not reflect the most recent data available at this site. See Also: "Selecting from the DUAL Table" for a description of the DUAL table See Also: TO_TIMESTAMP on page 5-201 for information on converting character data to TIMESTAMP data
- 52. Datatypes 2-18 Oracle Database SQL Reference TIMESTAMP WITH LOCAL TIME ZONE Datatype TIMESTAMP WITH LOCAL TIME ZONE is another variant of TIMESTAMP that includes a time zone offset in its value. It differs from TIMESTAMP WITH TIME ZONE in that data stored in the database is normalized to the database time zone, and the time zone offset is not stored as part of the column data. When a user retrieves the data, Oracle returns it in the user's local session time zone. The time zone offset is the difference (in hours and minutes) between local time and UTC (Coordinated Universal Time—formerly Greenwich Mean Time). This datatype is useful for displaying date information in the time zone of the client system in a two-tier application. Specify the TIMESTAMP WITH LOCAL TIME ZONE datatype as follows: TIMESTAMP [(fractional_seconds_precision)] WITH LOCAL TIME ZONE where fractional_seconds_precision optionally specifies the number of digits Oracle stores in the fractional part of the SECOND datetime field. When you create a column of this datatype, the value can be a number in the range 0 to 9. The default is 6. Oracle time zone data is derived from the public domain information available at ftp://elsie.nci.nih.gov/pub/. Oracle time zone data may not reflect the most recent data available at this site. INTERVAL YEAR TO MONTH Datatype INTERVAL YEAR TO MONTH stores a period of time using the YEAR and MONTH datetime fields. This datatype is useful for representing the difference between two datetime values when only the year and month values are significant. Specify INTERVAL YEAR TO MONTH as follows: INTERVAL YEAR [(year_precision)] TO MONTH where year_precision is the number of digits in the YEAR datetime field. The default value of year_precision is 2. You have a great deal of flexibility when specifying interval values as literals. Please refer to "Interval Literals" on page 2-51 for detailed information on specify interval See Also: ■ Oracle Database Globalization Support Guide for more information on Oracle time zone data ■ "Support for Daylight Saving Times" on page 2-21 and Table 2–15, " Datetime Format Elements" on page 2-59 for information on daylight saving support ■ TO_TIMESTAMP_TZ on page 5-202 for information on converting character data to TIMESTAMP WITH TIME ZONE data ■ ALTER SESSION on page 11-45 for information on the ERROR_ ON_OVERLAP_TIME session parameter See Also: ■ Oracle Database Globalization Support Guide for more information on Oracle time zone data ■ Oracle Database Application Developer's Guide - Fundamentals for examples of using this datatype and CAST on page 5-24 for information on converting character data to TIMESTAMP WITH LOCAL TIME ZONE
- 53. Datatypes Basic Elements of Oracle SQL 2-19 values as literals. Also see "Datetime and Interval Examples" on page 2-22 for an example using intervals. INTERVAL DAY TO SECOND Datatype INTERVAL DAY TO SECOND stores a period of time in terms of days, hours, minutes, and seconds. This datatype is useful for representing the precise difference between two datetime values. Specify this datatype as follows: INTERVAL DAY [(day_precision)] TO SECOND [(fractional_seconds_precision)] where ■ day_precision is the number of digits in the DAY datetime field. Accepted values are 0 to 9. The default is 2. ■ fractional_seconds_precision is the number of digits in the fractional part of the SECOND datetime field. Accepted values are 0 to 9. The default is 6. You have a great deal of flexibility when specifying interval values as literals. Please refer to "Interval Literals" on page 2-51 for detailed information on specify interval values as literals. Also see "Datetime and Interval Examples" on page 2-22 for an example using intervals. Datetime/Interval Arithmetic You can perform a number of arithmetic operations on date (DATE), timestamp (TIMESTAMP, TIMESTAMP WITH TIME ZONE, and TIMESTAMP WITH LOCAL TIME ZONE) and interval (INTERVAL DAY TO SECOND and INTERVAL YEAR TO MONTH) data. Oracle calculates the results based on the following rules: ■ You can use NUMBER constants in arithmetic operations on date and timestamp values, but not interval values. Oracle internally converts timestamp values to date values and interprets NUMBER constants in arithmetic datetime and interval expressions as numbers of days. For example, SYSDATE + 1 is tomorrow. SYSDATE - 7 is one week ago. SYSDATE + (10/1440) is ten minutes from now. Subtracting the hire_date column of the sample table employees from SYSDATE returns the number of days since each employee was hired. You cannot multiply or divide date or timestamp values. ■ Oracle implicitly converts BINARY_FLOAT and BINARY_DOUBLE operands to NUMBER. ■ Each DATE value contains a time component, and the result of many date operations include a fraction. This fraction means a portion of one day. For example, 1.5 days is 36 hours. These fractions are also returned by Oracle built-in functions for common operations on DATE data. For example, the MONTHS_ BETWEEN function returns the number of months between two dates. The fractional portion of the result represents that portion of a 31-day month. ■ If one operand is a DATE value or a numeric value (neither of which contains time zone or fractional seconds components), then: – Oracle implicitly converts the other operand to DATE data. (The exception is multiplication of a numeric value times an interval, which returns an interval.) – If the other operand has a time zone value, then Oracle uses the session time zone in the returned value.
- 54. Datatypes 2-20 Oracle Database SQL Reference – If the other operand has a fractional seconds value, then the fractional seconds value is lost. ■ When you pass a timestamp, interval, or numeric value to a built-in function that was designed only for the DATE datatype, Oracle implicitly converts the non-DATE value to a DATE value. Please refer to "Datetime Functions" on page 5-4 for information on which functions cause implicit conversion to DATE. ■ When interval calculations return a datetime value, the result must be an actual datetime value or the database returns an error. For example, the next two statements return errors: SELECT TO_DATE('31-AUG-2004','DD-MON-YYYY') + TO_YMINTERVAL('0-1') FROM DUAL; SELECT TO_DATE('29-FEB-2004','DD-MON-YYYY') + TO_YMINTERVAL('1-0') FROM DUAL; The first fails because adding one month to a 31-day month would result in September 31, which is not a valid date. The second fails because adding one year to a date that exists only every four years is not valid. However, the next statement succeeds, because adding four years to a February 29 date is valid: SELECT TO_DATE('29-FEB-2004', 'DD-MON-YYYY') + TO_YMINTERVAL('4-0') FROM DUAL; TO_DATE(' --------- 29-FEB-08 ■ Oracle performs all timestamp arithmetic in UTC time. For TIMESTAMP WITH LOCAL TIME ZONE, Oracle converts the datetime value from the database time zone to UTC and converts back to the database time zone after performing the arithmetic. For TIMESTAMP WITH TIME ZONE, the datetime value is always in UTC, so no conversion is necessary. Table 2–5 is a matrix of datetime arithmetic operations. Dashes represent operations that are not supported. Table 2–5 Matrix of Datetime Arithmetic Operand & Operator DATE TIMESTAMP INTERVAL Numeric DATE — — — — + — — DATE DATE - DATE DATE DATE DATE * — — — — / — — — — TIMESTAMP — — — — + — — TIMESTAMP — - INTERVAL INTERVAL TIMESTAMP TIMESTAMP * — — — — / — — — — INTERVAL — — — — + DATE TIMESTAMP INTERVAL — - — — INTERVAL — * — — — INTERVAL
- 55. Datatypes Basic Elements of Oracle SQL 2-21 Examples You can add an interval value expression to a start time. Consider the sample table oe.orders with a column order_date. The following statement adds 30 days to the value of the order_date column: SELECT order_id, order_date + INTERVAL '30' DAY FROM orders; Support for Daylight Saving Times Oracle Database automatically determines, for any given time zone region, whether daylight saving is in effect and returns local time values accordingly. The datetime value is sufficient for Oracle to determine whether daylight saving time is in effect for a given region in all cases except boundary cases. A boundary case occurs during the period when daylight saving goes into or comes out of effect. For example, in the US-Pacific region, when daylight saving goes into effect, the time changes from 2:00 a.m. to 3:00 a.m. The one hour interval between 2 and 3 a.m. does not exist. When daylight saving goes out of effect, the time changes from 2:00 a.m. back to 1:00 a.m., and the one-hour interval between 1 and 2 a.m. is repeated. To resolve these boundary cases, Oracle uses the TZR and TZD format elements, as described in Table 2–15. TZR represents the time zone region in datetime input strings. Examples are 'Australia/North', 'UTC', and 'Singapore'. TZD represents an abbreviated form of the time zone region with daylight saving information. Examples are 'PST' for US/Pacific standard time and 'PDT' for US/Pacific daylight time. To see a listing of valid values for the TZR and TZD format elements, query the TZNAME and TZABBREV columns of the V$TIMEZONE_NAMES dynamic performance view. Timezone region names are needed by the daylight saving feature. The region names are stored in two time zone files. The default time zone file is the complete (larger) file containing all time zones. The other time zone file is a small file containing only the most common time zones to maximize performance. If your time zone is in the small file, and you want to maximize performance, then you must provide a path to the small file by way of the ORA_TZFILE environment variable. Please refer to Oracle Database Administrator's Guide for more information about setting the ORA_TZFILE environment variable. For a complete listing of the timezone region names in both files, please refer to Oracle Database Globalization Support Guide. Oracle time zone data is derived from the public domain information available at ftp://elsie.nci.nih.gov/pub/. Oracle time zone data may not reflect the most recent data available at this site. / — — — INTERVAL Numeric — — — — + DATE DATE — NA - — — — NA * — — INTERVAL NA / — — — NA Table 2–5 (Cont.) Matrix of Datetime Arithmetic Operand & Operator DATE TIMESTAMP INTERVAL Numeric
- 56. Datatypes 2-22 Oracle Database SQL Reference Datetime and Interval Examples The following example shows how to declare some datetime and interval datatypes. CREATE TABLE time_table ( start_time TIMESTAMP, duration_1 INTERVAL DAY (6) TO SECOND (5), duration_2 INTERVAL YEAR TO MONTH); The start_time column is of type TIMESTAMP. The implicit fractional seconds precision of TIMESTAMP is 6. The duration_1 column is of type INTERVAL DAY TO SECOND. The maximum number of digits in field DAY is 6 and the maximum number of digits in the fractional second is 5. The maximum number of digits in all other datetime fields is 2. The duration_2 column is of type INTERVAL YEAR TO MONTH. The maximum number of digits of the value in each field (YEAR and MONTH) is 2. Interval datatypes do not have format models. Therefore, to adjust their presentation, you must combine character functions such as EXTRACT and concatenate the components. For example, the following examples query the hr.employees and oe.orders tables, respectively, and change interval output from the form "yy-mm" to "yy years mm months" and from "dd-hh" to "dddd days hh hours": SELECT last_name, EXTRACT(YEAR FROM (SYSDATE - hire_date) YEAR TO MONTH ) || ' years ' || EXTRACT(MONTH FROM (SYSDATE - hire_date) YEAR TO MONTH ) || ' months' "Interval" FROM employees ; LAST_NAME Interval ------------------------- -------------------- King 17 years 11 months Kochhar 15 years 8 months De Haan 12 years 4 months Hunold 15 years 4 months Ernst 14 years 0 months Austin 7 years 11 months Pataballa 7 years 3 months Lorentz 6 years 3 months Greenberg 10 years 9 months . . . SELECT order_id, EXTRACT(DAY FROM (SYSDATE - order_date) DAY TO SECOND ) || ' days ' || EXTRACT(HOUR FROM (SYSDATE - order_date) DAY TO SECOND ) || ' hours' "Interval" FROM orders; See Also: ■ "Datetime Format Models" on page 2-58 for information on the format elements and the session parameter ERROR_ON_ OVERLAP_TIME on page 11-53. ■ Oracle Database Globalization Support Guide for more information on Oracle time zone data ■ Oracle Database Reference for information on the dynamic performance views
- 57. Datatypes Basic Elements of Oracle SQL 2-23 ORDER_ID Interval ---------- -------------------- 2458 2095 days 18 hours 2397 2000 days 17 hours 2454 2048 days 16 hours 2354 1762 days 16 hours 2358 1950 days 15 hours 2381 1823 days 13 hours 2440 2080 days 12 hours 2357 2680 days 11 hours 2394 1917 days 10 hours 2435 2078 days 10 hours . . . RAW and LONG RAW Datatypes The RAW and LONG RAW datatypes store data that is not to be interpreted (that is, not explicitly converted when moving data between different systems) by Oracle Database. These datatypes are intended for binary data or byte strings. For example, you can use LONG RAW to store graphics, sound, documents, or arrays of binary data, for which the interpretation is dependent on the use. Oracle strongly recommends that you convert LONG RAW columns to binary LOB (BLOB) columns. LOB columns are subject to far fewer restrictions than LONG columns. See TO_LOB on page 5-196 for more information. RAW is a variable-length datatype like VARCHAR2, except that Oracle Net (which connects user sessions to the instance) and the Import and Export utilities do not perform character conversion when transmitting RAW or LONG RAW data. In contrast, Oracle Net and Import/Export automatically convert CHAR, VARCHAR2, and LONG data from the database character set to the user session character set (which you can set with the NLS_LANGUAGE parameter of the ALTER SESSION statement), if the two character sets are different. When Oracle automatically converts RAW or LONG RAW data to and from CHAR data, the binary data is represented in hexadecimal form, with one hexadecimal character representing every four bits of RAW data. For example, one byte of RAW data with bits 11001011 is displayed and entered as CB. Large Object (LOB) Datatypes The built-in LOB datatypes BLOB, CLOB, and NCLOB (stored internally) and BFILE (stored externally) can store large and unstructured data such as text, image, video, and spatial data. The size of BLOB, CLOB, and NCLOB data can be up to (4 gigabytes -1) * (the value of the CHUNK parameter of LOB storage). If the tablespaces in your database are of standard block size, and if you have used the default value of the CHUNK parameter of LOB storage when creating a LOB column, then this is equivalent to (4 gigabytes - 1) * (database block size). BFILE data can be up to 232 -1 bytes, although your operating system may impose restrictions on this maximum. When creating a table, you can optionally specify different tablespace and storage characteristics for LOB columns or LOB object attributes from those specified for the table. LOB columns contain LOB locators that can refer to in-line (in the database) or out-of-line (outside the database) LOB values. Selecting a LOB from a table actually returns the LOB locator and not the entire LOB value. The DBMS_LOB package and Oracle Call Interface (OCI) operations on LOBs are performed through these locators.
- 58. Datatypes 2-24 Oracle Database SQL Reference LOBs are similar to LONG and LONG RAW types, but differ in the following ways: ■ LOBs can be attributes of an object type (user-defined datatype). ■ The LOB locator is stored in the table column, either with or without the actual LOB value. BLOB, NCLOB, and CLOB values can be stored in separate tablespaces. BFILE data is stored in an external file on the server. ■ When you access a LOB column, the locator is returned. ■ A LOB can be up to (4 gigabytes - 1)*(database block size) in size. BFILE data can be up to 232 -1 bytes, although your operating system may impose restrictions on this maximum. Preceding corrected; thomas.chang, 8/26/04. ■ LOBs permit efficient, random, piece-wise access to and manipulation of data. ■ You can define more than one LOB column in a table. ■ With the exception of NCLOB, you can define one or more LOB attributes in an object. ■ You can declare LOB bind variables. ■ You can select LOB columns and LOB attributes. ■ You can insert a new row or update an existing row that contains one or more LOB columns or an object with one or more LOB attributes. In update operations, you can set the internal LOB value to NULL, empty, or replace the entire LOB with data. You can set the BFILE to NULL or make it point to a different file. ■ You can update a LOB row-column intersection or a LOB attribute with another LOB row-column intersection or LOB attribute. ■ You can delete a row containing a LOB column or LOB attribute and thereby also delete the LOB value. For BFILEs, the actual operating system file is not deleted. You can access and populate rows of an in-line LOB column (a LOB column stored in the database) or a LOB attribute (an attribute of an object type column stored in the database) simply by issuing an INSERT or UPDATE statement. Restrictions on LOB Columns LOB columns are subject to the following restrictions: ■ You cannot specify a LOB as a primary key column. ■ Oracle Database has limited support for remote LOBs. Remote LOBs are supported in three ways.. 1. Create table as select or insert as select. CREATE TABLE t AS SELECT * FROM table1@remote_site; INSERT INTO t SELECT * FROM table1@remote_site; UPDATE t SET lobcol = (SELECT lobcol FROM table1@remote_site); INSERT INTO table1@remote_site SELECT * FROM local_table; UPDATE table1@remote_site SET lobcol = (SELECT lobcol FROM local_table); DELETE FROM table1@remote_site <WHERE clause involving non_lob_columns> In statements structured like the preceding examples, only standalone LOB columns are allowed in the select list. 2. Functions on remote LOBs returning scalars. SQL and PL/SQL functions having a LOB parameter and returning a scalar datatype are supported. Other SQL functions and DBMS_LOB APIs are not supported for use with remote LOB columns. For example, the following statement is supported:
- 59. Datatypes Basic Elements of Oracle SQL 2-25 CREATE TABLE tab AS SELECT DBMS_LOB.GETLENGTH@dbs2(clob_col) len FROM tab@dbs2; CREATE TABLE tab AS SELECT LENGTH(clob_col) len FROM tab@dbs2; However, the following statement is not supported because DBMS_LOB.SUBSTR returns a LOB: CREATE TABLE tab AS SELECT DBMS_LOB.SUBSTR(clob_col) from tab@dbs2; 3. Data Interface for remote LOBs. You can insert a character or binary buffer into a remote CLOB or BLOB, and select a remote CLOB or BLOB into a character or binary buffer. For example (in PL/SQL): SELECT clobcol1, type1.blobattr INTO varchar_buf1, raw_buf2 FROM table1@remote_site; INSERT INTO table1@remotesite (clobcol1, type1.blobattr) VALUES varchar_buf1, raw_buf2; INSERT INTO table1@remotesite (lobcol) VALUES (’test’); UPDATE table1 SET lobcol = ’xxx’; These are the only supported syntax involving LOBs in remote tables. No other usage is supported. ■ Clusters cannot contain LOBs, either as key or non-key columns. ■ The following data structures are supported only as temporary instances. You cannot store these instances in database tables: – VARRAY of any LOB type – VARRAY of any type containing a LOB type, such as an object type with a LOB attribute – ANYDATA of any LOB type – ANYDATA of any type containing a LOB ■ You cannot specify LOB columns in the ORDER BY clause of a query, or in the GROUP BY clause of a query or in an aggregate function. ■ You cannot specify a LOB column in a SELECT... DISTINCT or SELECT... UNIQUE statement or in a join. However, you can specify a LOB attribute of an object type column in a SELECT... DISTINCT statement or in a query that uses the UNION or MINUS set operator if the column's object type has a MAP or ORDER function defined on it. ■ You cannot specify LOB columns in ANALYZE... COMPUTE or ANALYZE... ESTIMATE statements. ■ The first (INITIAL) extent of a LOB segment must contain at least three database blocks. ■ When creating an UPDATE DML trigger, you cannot specify a LOB column in the UPDATE OF clause. ■ You cannot specify a LOB column as part of an index key. However, you can specify a LOB column in the indextype specification of a domain index. In addition, Oracle Text lets you define an index on a CLOB column. ■ In an INSERT... AS SELECT operation, you can bind up to 4000 bytes of data to LOB columns and attributes. ■ If a table has both LONG and LOB columns, you cannot bind more than 4000 bytes of data to both the LONG and LOB columns in the same SQL statement. However, you can bind more than 4000 bytes of data to either the LONG or the LOB column.
- 60. Datatypes 2-26 Oracle Database SQL Reference BFILE Datatype The BFILE datatype enables access to binary file LOBs that are stored in file systems outside Oracle Database. A BFILE column or attribute stores a BFILE locator, which serves as a pointer to a binary file on the server file system. The locator maintains the directory name and the filename. You can change the filename and path of a BFILE without affecting the base table by using the BFILENAME function. Please refer to BFILENAME on page 5-21 for more information on this built-in SQL function. Correction in last sentence below; thomas.chang, 8/26/04. Binary file LOBs do not participate in transactions and are not recoverable. Rather, the underlying operating system provides file integrity and durability. BFILE data can be up to 232 -1 bytes, although your operating system may impose restrictions on this maximum. The database administrator must ensure that the external file exists and that Oracle processes have operating system read permissions on the file. The BFILE datatype enables read-only support of large binary files. You cannot modify or replicate such a file. Oracle provides APIs to access file data. The primary interfaces that you use to access file data are the DBMS_LOB package and the Oracle Call Interface (OCI). BLOB Datatype The BLOB datatype stores unstructured binary large objects. BLOB objects can be thought of as bitstreams with no character set semantics. BLOB objects can store binary data up to (4 gigabytes -1) * (the value of the CHUNK parameter of LOB storage). If the tablespaces in your database are of standard block size, and if you have used the default value of the CHUNK parameter of LOB storage when creating a LOB column, then this is equivalent to (4 gigabytes - 1) * (database block size). BLOB objects have full transactional support. Changes made through SQL, the DBMS_ LOB package, or the Oracle Call Interface (OCI) participate fully in the transaction. BLOB value manipulations can be committed and rolled back. However, you cannot save a BLOB locator in a PL/SQL or OCI variable in one transaction and then use it in another transaction or session. Note: For a table on which you have defined a DML trigger, if you use OCI functions or DBMS_LOB routines to change the value of a LOB column or the LOB attribute of an object type column, then the database does not fire the DML trigger. See Also: ■ Oracle Database PL/SQL Packages and Types Reference and Oracle Call Interface Programmer's Guide for more information about these interfaces and LOBs ■ the modify_col_properties clause of ALTER TABLE on page 12-2 and TO_LOB on page 5-196 for more information on converting LONG columns to LOB columns See Also: Oracle Database Application Developer's Guide - Large Objects and Oracle Call Interface Programmer's Guide for more information about LOBs and CREATE DIRECTORY on page 14-42
- 61. Datatypes Basic Elements of Oracle SQL 2-27 CLOB Datatype The CLOB datatype stores single-byte and multibyte character data. Both fixed-width and variable-width character sets are supported, and both use the database character set. CLOB objects can store up to (4 gigabytes -1) * (the value of the CHUNK parameter of LOB storage) of character data. If the tablespaces in your database are of standard block size, and if you have used the default value of the CHUNK parameter of LOB storage when creating a LOB column, then this is equivalent to (4 gigabytes - 1) * (database block size). CLOB objects have full transactional support. Changes made through SQL, the DBMS_ LOB package, or the Oracle Call Interface (OCI) participate fully in the transaction. CLOB value manipulations can be committed and rolled back. However, you cannot save a CLOB locator in a PL/SQL or OCI variable in one transaction and then use it in another transaction or session. NCLOB Datatype The NCLOB datatype stores Unicode data. Both fixed-width and variable-width character sets are supported, and both use the national character set. NCLOB objects can store up to (4 gigabytes -1) * (the value of the CHUNK parameter of LOB storage) of character text data. If the tablespaces in your database are of standard block size, and if you have used the default value of the CHUNK parameter of LOB storage when creating a LOB column, then this is equivalent to (4 gigabytes - 1) * (database block size)(4 gigabytes-1) * (database block size). NCLOB objects have full transactional support. Changes made through SQL, the DBMS_ LOB package, or the OCI participate fully in the transaction. NCLOB value manipulations can be committed and rolled back. However, you cannot save an NCLOB locator in a PL/SQL or OCI variable in one transaction and then use it in another transaction or session. ROWID Datatype Each row in the database has an address. You can examine a row address by querying the pseudocolumn ROWID. Values of this pseudocolumn are strings representing the address of each row. These strings have the datatype ROWID. You can also create tables and clusters that contain actual columns having the ROWID datatype. Oracle Database does not guarantee that the values of such columns are valid rowids. Please refer to Chapter 3, "Pseudocolumns" for more information on the ROWID pseudocolumn. Restricted Rowids Beginning with Oracle8, Oracle SQL incorporated an extended format for rowids to efficiently support partitioned tables and indexes and tablespace-relative data block addresses (DBAs) without ambiguity. Character values representing rowids in Oracle7 and earlier releases are called restricted rowids. Their format is as follows: block.row.file where: ■ block is a hexadecimal string identifying the data block of the datafile containing the row. The length of this string depends on your operating system. See Also: Oracle Database Globalization Support Guide for information on Unicode datatype support
- 62. Datatypes 2-28 Oracle Database SQL Reference ■ row is a four-digit hexadecimal string identifying the row in the data block. The first row of the block has a digit of 0. ■ file is a hexadecimal string identifying the database file containing the row. The first datafile has the number 1. The length of this string depends on your operating system. Extended Rowids The extended ROWID datatype stored in a user column includes the data in the restricted rowid plus a data object number. The data object number is an identification number assigned to every database segment. You can retrieve the data object number from the data dictionary views USER_OBJECTS, DBA_OBJECTS, and ALL_OBJECTS. Objects that share the same segment (clustered tables in the same cluster, for example) have the same object number. Extended rowids are stored as base 64 values that can contain the characters A-Z, a-z, 0-9, and the plus sign (+) and forward slash (/). Extended rowids are not available directly. You can use a supplied package, DBMS_ROWID, to interpret extended rowid contents. The package functions extract and provide information that would be available directly from a restricted rowid as well as information specific to extended rowids. Compatibility and Migration The restricted form of a rowid is still supported in this release for backward compatibility, but all tables return rowids in the extended format. UROWID Datatype Each row in a database has an address. However, the rows of some tables have addresses that are not physical or permanent or were not generated by Oracle Database. For example, the row addresses of index-organized tables are stored in index leaves, which can move. Rowids of foreign tables (such as DB2 tables accessed through a gateway) are not standard Oracle rowids. Oracle uses universal rowids (urowids) to store the addresses of index-organized and foreign tables. Index-organized tables have logical urowids and foreign tables have foreign urowids. Both types of urowid are stored in the ROWID pseudocolumn (as are the physical rowids of heap-organized tables). Oracle creates logical rowids based on the primary key of the table. The logical rowids do not change as long as the primary key does not change. The ROWID pseudocolumn of an index-organized table has a datatype of UROWID. You can access this pseudocolumn as you would the ROWID pseudocolumn of a heap-organized table (that is, using a SELECT ... ROWID statement). If you want to store the rowids of an index-organized table, then you can define a column of type UROWID for the table and retrieve the value of the ROWID pseudocolumn into that column. See Also: Oracle Database PL/SQL Packages and Types Reference for information on the functions available with the DBMS_ROWID package and how to use them See Also: Oracle Database Upgrade Guide for information regarding compatibility and migration issues
- 63. Datatypes Basic Elements of Oracle SQL 2-29 ANSI, DB2, and SQL/DS Datatypes SQL statements that create tables and clusters can also use ANSI datatypes and datatypes from the IBM products SQL/DS and DB2. Oracle recognizes the ANSI or IBM datatype name that differs from the Oracle Database datatype name, records it as the name of the datatype of the column, and then stores the column data in an Oracle datatype based on the conversions shown in the tables that follow. Notes: a. The NUMERIC and DECIMAL datatypes can specify only fixed-point numbers. For those datatypes, s defaults to 0. b. The FLOAT datatype is a floating-point number with a binary precision b. The default precision for this datatypes is 126 binary, or 38 decimal. c. The DOUBLE PRECISION datatype is a floating-point number with binary precision 126. d. The REAL datatype is a floating-point number with a binary precision of 63, or 18 decimal. Note: Heap-organized tables have physical rowids. Oracle does not recommend that you specify a column of datatype UROWID for a heap-organized table. See Also: Oracle Database Concepts for more information on universal rowids and "ROWID Datatype" on page 2-27 for a discussion of the address of database rows Table 2–6 ANSI Datatypes Converted to Oracle Datatypes ANSI SQL Datatype Oracle Datatype CHARACTER(n) CHAR(n) CHAR(n) CHARACTER VARYING(n) CHAR VARYING(n) VARCHAR(n) NATIONAL CHARACTER(n) NATIONAL CHAR(n) NCHAR(n) NCHAR(n) NATIONAL CHARACTER VARYING(n) NATIONAL CHAR VARYING(n) NCHAR VARYING(n) NVARCHAR2(n) NUMERIC(p,s) DECIMAL(p,s) (a) NUMBER(p,s) INTEGER INT SMALLINT NUMBER(38) FLOAT (b) DOUBLE PRECISION (c) REAL (d) NUMBER
- 64. Datatypes 2-30 Oracle Database SQL Reference Notes: a. The DECIMAL datatype can specify only fixed-point numbers. For this datatype, s defaults to 0.. b. The FLOAT datatype is a floating-point number with a binary precision b. The default precision for this datatype is 126 binary or 38 decimal. Do not define columns with the following SQL/DS and DB2 datatypes, because they have no corresponding Oracle datatype: ■ GRAPHIC ■ LONG VARGRAPHIC ■ VARGRAPHIC ■ TIME Note that data of type TIME can also be expressed as Oracle datetime data. User-Defined Types User-defined datatypes use Oracle built-in datatypes and other user-defined datatypes as the building blocks of object types that model the structure and behavior of data in applications. The sections that follow describe the various categories of user-defined types. Object Types Object types are abstractions of the real-world entities, such as purchase orders, that application programs deal with. An object type is a schema object with three kinds of components: ■ A name, which identifies the object type uniquely within that schema. Table 2–7 SQL/DS and DB2 Datatypes Converted to Oracle Datatypes SQL/DS or DB2 Datatype Oracle Datatype CHARACTER(n) CHAR(n) VARCHAR(n) VARCHAR(n) LONG VARCHAR(n) LONG DECIMAL(p,s) (a) NUMBER(p,s) INTEGER SMALLINT NUMBER(38) FLOAT (b) NUMBER See Also: Datatypes in Oracle Database SQL Reference See Also: ■ Oracle Database Concepts for information about Oracle built-in datatypes ■ CREATE TYPE on page 17-3 and the CREATE TYPE BODY on page 17-21 for information about creating user-defined types ■ Oracle Database Application Developer's Guide - Fundamentals for information about using user-defined types
- 65. Datatypes Basic Elements of Oracle SQL 2-31 ■ Attributes, which are built-in types or other user-defined types. Attributes model the structure of the real-world entity. ■ Methods, which are functions or procedures written in PL/SQL and stored in the database, or written in a language like C or Java and stored externally. Methods implement operations the application can perform on the real-world entity. REF Datatypes An object identifier (represented by the keyword OID) uniquely identifies an object and enables you to reference the object from other objects or from relational tables. A datatype category called REF represents such references. A REF datatype is a container for an object identifier. REF values are pointers to objects. When a REF value points to a nonexistent object, the REF is said to be "dangling". A dangling REF is different from a null REF. To determine whether a REF is dangling or not, use the condition IS [NOT] DANGLING. For example, given object view oc_ orders in the sample schema oe, the column customer_ref is of type REF to type customer_typ, which has an attribute cust_email: SELECT o.customer_ref.cust_email FROM oc_orders o WHERE o.customer_ref IS NOT DANGLING; Varrays An array is an ordered set of data elements. All elements of a given array are of the same datatype. Each element has an index, which is a number corresponding to the position of the element in the array. The number of elements in an array is the size of the array. Oracle arrays are of variable size, which is why they are called varrays. You must specify a maximum size when you declare the varray. When you declare a varray, it does not allocate space. It defines a type, which you can use as: ■ The datatype of a column of a relational table ■ An object type attribute ■ A PL/SQL variable, parameter, or function return type Oracle normally stores an array object either in line (that is, as part of the row data) or out of line (in a LOB), depending on its size. However, if you specify separate storage characteristics for a varray, then Oracle stores it out of line, regardless of its size. Please refer to the varray_col_properties of CREATE TABLE on page 16-34 for more information about varray storage. Nested Tables A nested table type models an unordered set of elements. The elements may be built-in types or user-defined types. You can view a nested table as a single-column table or, if the nested table is an object type, as a multicolumn table, with a column for each attribute of the object type. A nested table definition does not allocate space. It defines a type, which you can use to declare: ■ The datatype of a column of a relational table ■ An object type attribute
- 66. Datatypes 2-32 Oracle Database SQL Reference ■ A PL/SQL variable, parameter, or function return type When a nested table appears as the type of a column in a relational table or as an attribute of the underlying object type of an object table, Oracle stores all of the nested table data in a single table, which it associates with the enclosing relational or object table. Oracle-Supplied Types Oracle provides SQL-based interfaces for defining new types when the built-in or ANSI-supported types are not sufficient. The behavior for these types can be implemented in C/C++, Java, or PL/ SQL. Oracle Database automatically provides the low-level infrastructure services needed for input-output, heterogeneous client-side access for new datatypes, and optimizations for data transfers between the application and the database. These interfaces can be used to build user-defined (or object) types and are also used by Oracle to create some commonly useful datatypes. Several such datatypes are supplied with the server, and they serve both broad horizontal application areas (for example, the Any types) and specific vertical ones (for example, the spatial types). The Oracle-supplied types, along with cross-references to the documentation of their implementation and use, are described in the following sections: ■ Any Types ■ XML Types ■ Spatial Types ■ Media Types Any Types The Any types provide highly flexible modeling of procedure parameters and table columns where the actual type is not known. These datatypes let you dynamically encapsulate and access type descriptions, data instances, and sets of data instances of any other SQL type. These types have OCI and PL/SQL interfaces for construction and access. ANYTYPE This type can contain a type description of any named SQL type or unnamed transient type. ANYDATA This type contains an instance of a given type, with data, plus a description of the type. ANYDATA can be used as a table column datatype and lets you store heterogeneous values in a single column. The values can be of SQL built-in types as well as user-defined types. ANYDATASET This type contains a description of a given type plus a set of data instances of that type. ANYDATASET can be used as a procedure parameter datatype where such flexibility is needed. The values of the data instances can be of SQL built-in types as well as user-defined types.
- 67. Datatypes Basic Elements of Oracle SQL 2-33 XML Types Extensible Markup Language (XML) is a standard format developed by the World Wide Web Consortium (W3C) for representing structured and unstructured data on the World Wide Web. Universal resource identifiers (URIs) identify resources such as Web pages anywhere on the Web. Oracle provides types to handle XML and URI data, as well as a class of URIs called DBURIRef types to access data stored within the database itself. It also provides a new set of types to store and access both external and internal URIs from within the database. XMLType This Oracle-supplied type can be used to store and query XML data in the database. XMLType has member functions you can use to access, extract, and query the XML data using XPath expressions. XPath is another standard developed by the W3C committee to traverse XML documents. Oracle XMLType functions support many W3C XPath expressions. Oracle also provides a set of SQL functions and PL/SQL packages to create XMLType values from existing relational or object-relational data. XMLType is a system-defined type, so you can use it as an argument of a function or as the datatype of a table or view column. You can also create tables and views of XMLType. When you create an XMLType column in a table, you can choose to store the XML data in a CLOB column or object relationally. You can also register the schema (using the DBMS_XMLSCHEMA package) and create a table or column conforming to the registered schema. In this case Oracle stores the XML data in underlying object-relational columns by default, but you can specify storage in a CLOB column even for schema-based data. Queries and DML on XMLType columns operate the same regardless of the storage mechanism. URI Datatypes Oracle supplies a family of URI types—URIType, DBURIType, XDBURIType, and HTTPURIType—which are related by an inheritance hierarchy. URIType is an object type and the others are subtypes of URIType. Since URIType is the supertype, you can create columns of this type and store DBURIType or HTTPURIType type instances in this column. HTTPURIType You can use HTTPURIType to store URLs to external Web pages or to files. Oracle accesses these files using HTTP (Hypertext Transfer Protocol). XDBURIType You can use XDBURIType to expose documents in the XML database hierarchy as URIs that can be embedded in any URIType column in a table. The XDBURIType consists of a URL, which comprises the hierarchical name of the XML document to which it refers and an optional fragment representing the XPath syntax. The fragment is separated from the URL part by a pound sign (#). The following lines are examples of XDBURIType: /home/oe/doc1.xml /home/oe/doc1.xml#/orders/order_item See Also: Oracle Database PL/SQL Packages and Types Reference for information on the ANYTYPE, ANYDATA, and ANYDATASET types See Also: Oracle XML DB Developer's Guide for information about using XMLType columns
- 68. Datatypes 2-34 Oracle Database SQL Reference DBURIType DBURIType can be used to store DBURIRef values, which reference data inside the database. Storing DBURIRef values lets you reference data stored inside or outside the database and access the data consistently. DBURIRef values use an XPath-like representation to reference data inside the database. If you imagine the database as an XML tree, then you would see the tables, rows, and columns as elements in the XML document. For example, the sample human resources user hr would see the following XML tree: <HR> <EMPLOYEES> <ROW> <EMPLOYEE_ID>205</EMPLOYEE_ID> <LAST_NAME>Higgins</LAST_NAME> <SALARY>12000</SALARY> .. <!-- other columns --> </ROW> ... <!-- other rows --> </EMPLOYEES> <!-- other tables..--> </HR> <!-- other user schemas on which you have some privilege on..--> The DBURIRef is an XPath expression over this virtual XML document. So to reference the SALARY value in the EMPLOYEES table for the employee with employee number 205, we can write a DBURIRef as, /HR/EMPLOYEES/ROW[EMPLOYEE_ID=205]/SALARY Using this model, you can reference data stored in CLOB columns or other columns and expose them as URLs to the external world. URIFactory Package Oracle also provides the URIFactory package, which can create and return instances of the various subtypes of the URITypes. The package analyzes the URL string, identifies the type of URL (HTTP, DBURI, and so on), and creates an instance of the subtype. To create a DBURI instance, the URL must start with the prefix /oradb. For example, URIFactory.getURI('/oradb/HR/EMPLOYEES') would create a DBURIType instance and URIFactory.getUri('/sys/schema') would create an XDBURIType instance. Spatial Types Oracle Spatial is designed to make spatial data management easier and more natural to users of location-enabled applications, geographic information system (GIS) applications, and geoimaging applications. After the spatial data is stored in an Oracle See Also: ■ Oracle Database Application Developer's Guide - Object-Relational Features for general information on object types and type inheritance ■ Oracle XML Developer's Kit Programmer's Guide for more information about these supplied types and their implementation ■ Oracle Streams Advanced Queuing User's Guide and Reference for information about using XMLType with Oracle Advanced Queuing
- 69. Datatypes Basic Elements of Oracle SQL 2-35 database, you can easily manipulate, retrieve, and relate it to all the other data stored in the database. The following datatypes are not available unless you have installed Oracle Spatial. SDO_GEOMETRY The geometric description of a spatial object is stored in a single row, in a single column of object type SDO_GEOMETRY in a user-defined table. Any table that has a column of type SDO_GEOMETRY must have another column, or set of columns, that defines a unique primary key for that table. Tables of this sort are sometimes called geometry tables. The SDO_GEOMETRY object type has the following definition: CREATE TYPE SDO_GEOMETRY AS OBJECT ( sgo_gtype NUMBER, sdo_srid NUMBER, sdo_point SDO_POINT_TYPE, sdo_elem_info SDO_ELEM_INFO_ARRAY, sdo_ordinates SDO_ORDINATE_ARRAY); SDO_TOPO_GEOMETRY This type describes a topology geometry, which is stored in a single row, in a single column of object type SDO_TOPO_GEOMETRY in a user-defined table. The SDO_TOPO_GEOMETRY object type has the following definition: CREATE TYPE SDO_TOPO_GEOMETRY AS OBJECT ( tg_type NUMBER, tg_id NUMBER, tg_layer_id NUMBER, topology_id NUMBER); SDO_GEORASTER In the GeoRaster object-relational model, a raster grid or image object is stored in a single row, in a single column of object type SDO_GEORASTER in a user-defined table. Tables of this sort are called GeoRaster tables. The SDO_GEORASTER object type has the following definition: CREATE TYPE SDO_GEORASTER AS OBJECT ( rasterType NUMBER, spatialExtent SDO_GEOMETRY, rasterDataTable VARCHAR2(32), rasterID NUMBER, metadata XMLType); Media Types Oracle interMedia uses object types, similar to Java or C++ classes, to describe multimedia data. An instance of these object types consists of attributes, including metadata and the media data, and methods. The interMedia datatypes are created in the ORDSYS schema. Public synonyms exist for all the datatypes, so you can access them without specifying the schema name. See Also: Oracle Spatial User's Guide and Reference, Oracle Spatial Topology and Network Data Models, and Oracle Spatial GeoRaster for information on the full implementation of the spatial datatypes and guidelines for using them
- 70. Datatypes 2-36 Oracle Database SQL Reference ORDAudio The ORDAUDIO object type supports the storage and management of audio data. ORDImage The ORDIMAGE object type supports the storage and management of image data. ORDImageSignature The ORDImageSignature object type supports a compact representation of the color, texture, and shape information of image data. ORDVideo The ORDVIDEO object type supports the storage and management of video data. ORDDoc The ORDDOC object type supports storage and management of any type of media data, including audio, image and video data. Use this type when you want all media to be stored in a single column. The following datatypes provide compliance with the ISO-IEC 13249-5 Still Image standard, commonly referred to as SQL/MM StillImage. SI_StillImage The SI_StillImage object type represents digital images with inherent image characteristics such as height, width, and format. SI_Color The SI_Color object type encapsulates color values. SI_AverageColor The SI_AverageColor object type represents a feature that characterizes an image by its average color. SI_ColorHistogram The SI_ColorHistogram object type represents a feature that characterizes an image by the relative frequencies of the colors exhibited by samples of the raw image. SI_PositionalColor Given an image divided into n by m rectangles, the SI_PositionalColor object type represents the feature that characterizes an image by the n by m most significant colors of the rectangles. SI_Texture The SI_Texture object type represents a feature that characterizes an image by the size of repeating items (coarseness), brightness variations (contrast), and predominant direction (directionality). See Also: Oracle interMedia Reference for information on the implementation of these types and guidelines for using them
- 71. Datatype Comparison Rules Basic Elements of Oracle SQL 2-37 SI_FeatureList The SI_FeatureList object type is a list containing up to four of the image features represented by the preceding object types (SI_AverageColor, SI_ ColorHistogram, SI_PositionalColor, and SI_Texture), where each feature is associated with a feature weight. Expression Filter Type The Oracle Expression Filter allows application developers to manage and evaluate conditional expressions that describe users' interests in data. The Expression Filter includes the following datatype: Expression Expression Filter uses a virtual datatype called Expression to manage and evaluate conditional expressions as data in database tables. The Expression Filter creates a column of Expression datatype from a VARCHAR2 column by assigning an attribute set to the column. This assignment enables a data constraint that ensures the validity of expressions stored in the column. You can define conditions using the EVALUATE operator on an Expression datatype to evaluate the expressions stored in a column for some data. If you are using Enterprise Edition, then you can also define an Expression Filter index on a column of Expression datatype to process queries using the EVALUATE operator. Datatype Comparison Rules This section describes how Oracle Database compares values of each datatype. Numeric Values A larger value is considered greater than a smaller one. All negative numbers are less than zero and all positive numbers. Thus, -1 is less than 100; -100 is less than -1. The floating-point value NaN (not a number) is greater than any other numeric value and is equal to itself. Date Values A later date is considered greater than an earlier one. For example, the date equivalent of '29-MAR-1997' is less than that of '05-JAN-1998' and '05-JAN-1998 1:35pm' is greater than '05-JAN-1998 10:09am'. Character Values Character values are compared on the basis of two measures: ■ Binary or linguistic sorting ■ Blank-padded or nonpadded comparison semantics See Also: Oracle Database Application Developer's Guide - Rules Manager and Expression Filter for more information on the Expression Filter See Also: "Numeric Precedence" on page 2-13 and "Floating-Point Numbers" on page 2-11 for more information on comparison semantics
- 72. Datatype Comparison Rules 2-38 Oracle Database SQL Reference The following subsections describe the two measures. Binary and Linguistic Sorting In binary sorting, which is the default, Oracle compares character strings according to the concatenated value of the numeric codes of the characters in the database character set. One character is greater than another if it has a greater numeric value than the other in the character set. Oracle considers blanks to be less than any character, which is true in most character sets. Linguistic sorting is useful if the binary sequence of numeric codes does not match the linguistic sequence of the characters you are comparing. Linguistic sorting is used if the NLS_COMP parameter is set to LINGUISTIC. In linguistic sorting, all SQL sorting and comparison are based on the linguistic rule specified by NLS_SORT. Blank-Padded and Nonpadded Comparison Semantics With blank-padded semantics, if the two values have different lengths, then Oracle first adds blanks to the end of the shorter one so their lengths are equal. Oracle then compares the values character by character up to the first character that differs. The value with the greater character in the first differing position is considered greater. If two values have no differing characters, then they are considered equal. This rule means that two values are equal if they differ only in the number of trailing blanks. Oracle uses blank-padded comparison semantics only when both values in the comparison are either expressions of datatype CHAR, NCHAR, text literals, or values returned by the USER function. With nonpadded semantics, Oracle compares two values character by character up to the first character that differs. The value with the greater character in that position is considered greater. If two values of different length are identical up to the end of the shorter one, then the longer value is considered greater. If two values of equal length have no differing characters, then the values are considered equal. Oracle uses nonpadded comparison semantics whenever one or both values in the comparison have the datatype VARCHAR2 or NVARCHAR2. The results of comparing two character values using different comparison semantics may vary. The table that follows shows the results of comparing five pairs of character values using each comparison semantic. Usually, the results of blank-padded and nonpadded comparisons are the same. The last comparison in the table illustrates the differences between the blank-padded and nonpadded comparison semantics. These are some common character sets: ■ 7-bit ASCII (American Standard Code for Information Interchange) ■ EBCDIC Code (Extended Binary Coded Decimal Interchange Code) See Also: Oracle Database Globalization Support Guide for more information about linguistic sorting Blank-Padded Nonpadded 'ac' > 'ab' 'ac' > 'ab' 'ab' > 'a ' 'ab' > 'a ' 'ab' > 'a' 'ab' > 'a' 'ab' = 'ab' 'ab' = 'ab' 'a ' = 'a' 'a ' > 'a'
- 73. Datatype Comparison Rules Basic Elements of Oracle SQL 2-39 ■ ISO 8859/1 (International Standards Organization) ■ JEUC Japan Extended UNIX Portions of the ASCII and EBCDIC character sets appear in Table 2–8 and Table 2–9. Uppercase and lowercase letters are not equivalent. The numeric values for the characters of a character set may not match the linguistic sequence for a particular language. Table 2–8 ASCII Character Set Symbol Decimal value Symbol Decimal value blank 32 ; 59 ! 33 < 60 " 34 = 61 # 35 > 62 $ 36 ? 63 % 37 @ 64 & 38 A-Z 65-90 ’ 39 [ 91 ( 40 92 ) 41 ] 93 * 42 ^ 94 + 43 _ 95 , 44 ‘ 96 - 45 a-z 97-122 . 46 { 123 / 47 | 124 0-9 48-57 } 125 : 58 ~ 126 Table 2–9 EBCDIC Character Set Symbol Decimal value Symbol Decimal value blank 64 % 108 ¢ 74 _ 109 . 75 > 110 < 76 ? 111 ( 77 : 122 + 78 # 123 | 79 @ 124 & 80 ' 125 ! 90 = 126 $ 91 " 127
- 74. Datatype Comparison Rules 2-40 Oracle Database SQL Reference Object Values Object values are compared using one of two comparison functions: MAP and ORDER. Both functions compare object type instances, but they are quite different from one another. These functions must be specified as part of any object type that will be compared with other object types. Varrays and Nested Tables Comparison of nested tables is described in "Comparison Conditions" on page 7-4. Datatype Precedence Oracle uses datatype precedence to determine implicit datatype conversion, which is discussed in the section that follows. Oracle datatypes take the following precedence: ■ Datetime and interval datatypes ■ BINARY_DOUBLE ■ BINARY_FLOAT ■ NUMBER ■ Character datatypes ■ All other built-in datatypes Data Conversion Generally an expression cannot contain values of different datatypes. For example, an expression cannot multiply 5 by 10 and then add 'JAMES'. However, Oracle supports both implicit and explicit conversion of values from one datatype to another. Implicit and Explicit Data Conversion Oracle recommends that you specify explicit conversions, rather than rely on implicit or automatic conversions, for these reasons: ■ SQL statements are easier to understand when you use explicit datatype conversion functions. ■ Implicit datatype conversion can have a negative impact on performance, especially if the datatype of a column value is converted to that of a constant rather than the other way around. * 92 a-i 129-137 ) 93 j-r 145-153 ; 94 s-z 162-169 ÿ 95 A-I 193-201 - 96 J-R 209-217 / 97 S-Z 226-233 See Also: CREATE TYPE on page 17-3 for a description of MAP and ORDER methods and the values they return Table 2–9 (Cont.) EBCDIC Character Set Symbol Decimal value Symbol Decimal value
- 75. Datatype Comparison Rules Basic Elements of Oracle SQL 2-41 ■ Implicit conversion depends on the context in which it occurs and may not work the same way in every case. For example, implicit conversion from a datetime value to a VARCHAR2 value may return an unexpected year depending on the value of the NLS_DATE_FORMAT parameter. ■ Algorithms for implicit conversion are subject to change across software releases and among Oracle products. Behavior of explicit conversions is more predictable. Implicit Data Conversion Oracle Database automatically converts a value from one datatype to another when such a conversion makes sense. Implicit conversion to character datatypes follows these rules: Table 2–10 is a matrix of Oracle implicit conversions. The table shows all possible conversions, without regard to the direction of the conversion or the context in which it is made. The rules governing these details follow the table. The following rules govern the direction in which Oracle Database makes implicit datatype conversions: ■ During INSERT and UPDATE operations, Oracle converts the value to the datatype of the affected column. ■ During SELECT FROM operations, Oracle converts the data from the column to the type of the target variable. ■ When manipulating numeric values, Oracle usually adjusts precision and scale to allow for maximum capacity. In such cases, the numeric datatype resulting from Table 2–10 Implicit Type Conversion Matrix CHAR VARCHAR2 NCHAR NVARCHAR2 DATE DATETIME/ INTERVAL NUMBER BINARY_FLOAT BINARY_DOUBLE LONG RAW ROWID CLOB BLOB NCLOB CHAR -- X X X X X X X X X X -- X X X VARCHAR2 X -- X X X X X X X X X X X -- X NCHAR X X -- X X X X X X X X X X -- X NVARCHAR2 X X X -- X X X X X X X X X -- X DATE X X X X -- -- -- -- -- -- -- -- -- -- -- DATETIME/ INTERVAL X X X X -- -- -- -- -- X -- -- -- -- -- NUMBER X X X X -- -- -- X X -- -- -- -- -- -- BINARY_ FLOAT X X X X -- -- X -- X -- -- -- -- -- -- BINARY_ DOUBLE X X X X -- -- X X -- -- -- -- -- -- -- LONG X X X X -- X -- -- -- -- X -- X -- X RAW X X X X -- -- -- -- -- X -- -- -- X -- ROWID -- X X X -- -- -- -- -- -- -- -- -- -- -- CLOB X X X X -- -- -- -- -- X -- -- -- -- X BLOB -- -- -- -- -- -- -- -- -- -- X -- -- -- -- NCLOB X X X X -- -- -- -- -- X -- -- X -- --
- 76. Datatype Comparison Rules 2-42 Oracle Database SQL Reference such operations can differ from the numeric datatype found in the underlying tables. ■ When comparing a character value with a numeric value, Oracle converts the character data to a numeric value. ■ Conversions between character values or NUMBER values and floating-point number values can be inexact, because the character types and NUMBER use decimal precision to represent the numeric value, and the floating-point numbers use binary precision. ■ When converting a CLOB value into a character datatype such as VARCHAR2, or converting BLOB to RAW data, if the data to be converted is larger than the target datatype, then the database returns an error. ■ Conversions from BINARY_FLOAT to BINARY_DOUBLE are exact. ■ Conversions from BINARY_DOUBLE to BINARY_FLOAT are inexact if the BINARY_ DOUBLE value uses more bits of precision that supported by the BINARY_FLOAT. ■ When comparing a character value with a DATE value, Oracle converts the character data to DATE. ■ When you use a SQL function or operator with an argument of a datatype other than the one it accepts, Oracle converts the argument to the accepted datatype. ■ When making assignments, Oracle converts the value on the right side of the equal sign (=) to the datatype of the target of the assignment on the left side. ■ During concatenation operations, Oracle converts from noncharacter datatypes to CHAR or NCHAR. ■ During arithmetic operations on and comparisons between character and noncharacter datatypes, Oracle converts from any character datatype to a numeric, date, or rowid, as appropriate. In arithmetic operations between CHAR/VARCHAR2 and NCHAR/NVARCHAR2, Oracle converts to a NUMBER. ■ Comparisons between CHAR and VARCHAR2 and between NCHAR and NVARCHAR2 types may entail different character sets. The default direction of conversion in such cases is from the database character set to the national character set. Table 2–11 shows the direction of implicit conversions between different character types. ■ Most SQL character functions are enabled to accept CLOBs as parameters, and Oracle performs implicit conversions between CLOB and character types. Therefore, functions that are not yet enabled for CLOBs can accept CLOBs through implicit conversion. In such cases, Oracle converts the CLOBs to CHAR or VARCHAR2 before the function is invoked. If the CLOB is larger than 4000 bytes, then Oracle converts only the first 4000 bytes to CHAR. User-defined types such as collections cannot be implicitly converted, but must be explicitly converted using CAST ... MULTISET Table 2–11 Conversion Direction of Different Character Types to CHAR to VARCHAR2 to NCHAR to NVARCHAR2 from CHAR -- VARCHAR2 NCHAR NVARCHAR2 from VARCHAR2 VARCHAR2 -- NVARCHAR2 NVARCHAR2 from NCHAR NCHAR NCHAR -- NVARCHAR2 from NVARCHAR2 NVARCHAR2 NVARCHAR2 NVARCHAR2 --
- 77. Datatype Comparison Rules Basic Elements of Oracle SQL 2-43 Implicit Data Conversion Examples Text Literal Example The text literal '10' has datatype CHAR. Oracle implicitly converts it to the NUMBER datatype if it appears in a numeric expression as in the following statement: SELECT salary + '10' FROM employees; Character and Number Values Example When a condition compares a character value and a NUMBER value, Oracle implicitly converts the character value to a NUMBER value, rather than converting the NUMBER value to a character value. In the following statement, Oracle implicitly converts '200' to 200: SELECT last_name FROM employees WHERE employee_id = '200'; Date Example In the following statement, Oracle implicitly converts '03-MAR-97' to a DATE value using the default date format 'DD-MON-YY': SELECT last_name FROM employees WHERE hire_date = '03-MAR-97'; Rowid Example In the following statement, Oracle implicitly converts the text literal 'AAAGH6AADAAAAFGAAN' to a rowid value. (Rowids are unique within a database, so to use this example you must know an actual rowid in your database.) SELECT last_name FROM employees WHERE ROWID = 'AAAGH6AADAAAAFGAAN'; Explicit Data Conversion You can explicitly specify datatype conversions using SQL conversion functions. Table 2–12 shows SQL functions that explicitly convert a value from one datatype to another. You cannot specify LONG and LONG RAW values in cases in which Oracle can perform implicit datatype conversion. For example, LONG and LONG RAW values cannot appear in expressions with functions or operators. Please refer to "LONG Datatype" on page 2-13 for information on the limitations on LONG and LONG RAW datatypes.
- 78. Literals 2-44 Oracle Database SQL Reference Literals The terms literal and constant value are synonymous and refer to a fixed data value. For example, 'JACK', 'BLUE ISLAND', and '101' are all character literals; 5001 is a numeric literal. Character literals are enclosed in single quotation marks so that Oracle can distinguish them from schema object names. This section contains these topics: Table 2–12 Explicit Type Conversions toCHAR, VARCHAR2, NCHAR, NVARCHAR2 toNUMBER toDatetime/ Interval toRAW toROWID toLONG, LONGRAW toCLOB,NCLOB, BLOB toBINARY_FLOAT toBINARY_DOUBLE from CHAR, VARCHAR2, NCHAR, NVARCHAR2 TO_CHAR (char.) TO_NCHAR (char.) TO_ NUMBER TO_DATE TO_TIMESTAMP TO_ TIMESTAMP_TZ TO_ YMINTERVAL TO_ DSINTERVAL HEXTORAW CHARTO= ROWID -- TO_CLOB TO_NCLOB TO_ BINARY_ FLOAT TO_ BINARY_ DOUBLE from NUMBER TO_CHAR (number) TO_NCHAR (number) -- TO_DATE NUMTOYM- INTERVAL NUMTODS- INTERVAL -- -- -- -- TO_ BINARY_ FLOAT TO_ BINARY_ DOUBLE from Datetime/ Interval TO_CHAR (date) TO_NCHAR (datetime) -- -- -- -- -- -- -- -- from RAW RAWTOHEX RAWTONHEX -- -- -- -- -- TO_BLOB -- -- from ROWID ROWIDTOCHAR -- -- -- -- -- -- -- -- from LONG / LONG RAW -- -- -- -- -- -- TO_LOB -- -- from CLOB, NCLOB, BLOB TO_CHAR TO_NCHAR -- -- -- -- -- TO_CLOB TO_NCLOB -- -- from CLOB, NCLOB, BLOB TO_CHAR TO_NCHAR -- -- -- -- -- TO_CLOB TO_NCLOB -- -- from BINARY_ FLOAT TO_CHAR (char.) TO_NCHAR (char.) TO_ NUMBER -- -- -- -- -- TO_ BINARY_ FLOAT TO_ BINARY_ DOUBLE from BINARY_ DOUBLE TO_CHAR (char.) TO_NCHAR (char.) TO_ NUMBER -- -- -- -- -- TO_ BINARY_ FLOAT TO_ BINARY_ DOUBLE See Also: "Conversion Functions" on page 5-5 for details on all of the explicit conversion functions
- 79. Literals Basic Elements of Oracle SQL 2-45 ■ Text Literals ■ Numeric Literals ■ Datetime Literals ■ Interval Literals Many SQL statements and functions require you to specify character and numeric literal values. You can also specify literals as part of expressions and conditions. You can specify character literals with the 'text' notation, national character literals with the N'text' notation, and numeric literals with the integer, or number notation, depending on the context of the literal. The syntactic forms of these notations appear in the sections that follow. To specify a datetime or interval datatype as a literal, you must take into account any optional precisions included in the datatypes. Examples of specifying datetime and interval datatypes as literals are provided in the relevant sections of "Datatypes" on page 2-1. Text Literals Use the text literal notation to specify values whenever 'string' or appears in the syntax of expressions, conditions, SQL functions, and SQL statements in other parts of this reference. This reference uses the terms text literal, character literal, and string interchangeably. Text, character, and string literals are always surrounded by single quotation marks. If the syntax uses the term char, you can specify either a text literal or another expression that resolves to character data — for example, the last_name column of the hr.employees table. When char appears in the syntax, the single quotation marks are not used. The syntax of text literals is as follows: text::= where N or n specifies the literal using the national character set (NCHAR or NVARCHAR2 data). By default, text entered using this notation is translated into the national character set by way of the database character set when used by the server. To avoid potential loss of data during the text literal conversion to the database character set, set the environment variable ORA_NCHAR_LITERAL_REPLACE to TRUE. Doing so transparently replaces the n’ internally and preserves the text literal for SQL processing. In the top branch of the syntax: ■ c is any member of the user's character set. A single quotation mark (') within the literal must be preceded by an escape character. To represent one single quotation mark within a literal, enter two single quotation marks. ■ ' ' are two single quotation marks that begin and end text literals. See Also: Oracle Database Globalization Support Guide for more information about N-quoted literals N n ’ c ’ Q q ’ quote_delimiter c quote_delimiter ’
- 80. Literals 2-46 Oracle Database SQL Reference In the bottom branch of the syntax: ■ Q or q indicates that the alternative quoting mechanism will be used. This mechanism allows a wide range of delimiters for the text string. ■ The outermost ' ' are two single quotation marks that precede and follow, respectively, the opening and closing quote_delimiter. ■ c is any member of the user's character set. You can include quotation marks (") in the text literal made up of c characters. You can also include the quote_ delimiter, as long as it is not immediately followed by a single quotation mark. ■ quote_delimiter is any single- or multibyte character except space, tab, and return. The quote_delimiter can be a single quotation mark. However, if the quote_delimiter appears in the text literal itself, ensure that it is not immediately followed by a single quotation mark. If the opening quote_delimiter is one of [, {, <, or (, then the closing quote_ delimiter must be the corresponding ], }, >, or ). In all other cases, the opening and closing quote_delimiter must be the same character. Text literals have properties of both the CHAR and VARCHAR2 datatypes: ■ Within expressions and conditions, Oracle treats text literals as though they have the datatype CHAR by comparing them using blank-padded comparison semantics. ■ A text literal can have a maximum length of 4000 bytes. Here are some valid text literals: 'Hello' 'ORACLE.dbs' 'Jackie''s raincoat' '09-MAR-98' N'nchar literal' Here are some valid text literals using the alternative quoting mechanism: q'!name LIKE '%DBMS_%%'!' q'<'So,' she said, 'It's finished.'>' q'{SELECT * FROM employees WHERE last_name = 'Smith';}' nq'ï Ÿ1234 ï' q'"name like '['"' Numeric Literals Use numeric literal notation to specify fixed and floating-point numbers. Integer Literals You must use the integer notation to specify an integer whenever integer appears in expressions, conditions, SQL functions, and SQL statements described in other parts of this reference. The syntax of integer is as follows: See Also: "Blank-Padded Comparison Semantics" on page -HIDDEN
- 81. Literals Basic Elements of Oracle SQL 2-47 integer::= where digit is one of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. An integer can store a maximum of 38 digits of precision. Here are some valid integers: 7 +255 NUMBER and Floating-Point Literals You must use the number or floating-point notation to specify values whenever number or n appears in expressions, conditions, SQL functions, and SQL statements in other parts of this reference. The syntax of number is as follows: number::= where ■ + or - indicates a positive or negative value. If you omit the sign, then a positive value is the default. ■ digit is one of 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9. ■ e or E indicates that the number is specified in scientific notation. The digits after the E specify the exponent. The exponent can range from -130 to 125. ■ f or F indicates that the number is a 32-bit binary floating point number (of type BINARY_FLOAT). ■ d or D indicates that the number is a 64-bit binary floating point number (of type BINARY_DOUBLE) If you omit f or F and d or D, then the number is of type NUMBER. The suffixes f (F) and d (D) are supported only in floating-point number literals, not in character strings that are to be converted to NUMBER. That is, if Oracle is expecting a NUMBER and it encounters the string '9', then it converts the string to the number 9. However, if Oracle encounters the string '9f', then conversion fails and an error is returned. + – digit + – digit . digit . digit e + – digit f d
- 82. Literals 2-48 Oracle Database SQL Reference A number of type NUMBER can store a maximum of 38 digits of precision. If the literal requires more precision than provided by NUMBER, BINARY_FLOAT, or BINARY_ DOUBLE, then Oracle truncates the value. If the range of the literal exceeds the range supported by NUMBER, BINARY_FLOAT, or BINARY_DOUBLE, then Oracle raises an error. If you have established a decimal character other than a period (.) with the initialization parameter NLS_NUMERIC_CHARACTERS, then you must specify numeric literals with 'text' notation. In these cases, Oracle automatically converts the text literal to a numeric value. For example, if the NLS_NUMERIC_CHARACTERS parameter specifies a decimal character of comma, specify the number 5.123 as follows: '5,123' Here are some valid NUMBER literals: 25 +6.34 0.5 25e-03 -1 Here are some valid floating-point number literals: 25f +6.34F 0.5d -1D You can also use the following supplied floating-point literals in situations where a value cannot be expressed as a numeric literal: Note: You cannot use this notation for floating-point number literals. See Also: ALTER SESSION on page 11-45 and Oracle Database Reference Literal Meaning Example binary_float_nan A value of type BINARY_FLOAT for which the condition IS NAN is true SELECT COUNT(*) FROM employees WHERE TO_BINARY_FLOAT(commission_pct) != BINARY_FLOAT_NAN; binary_float_ infinity Single-precision positive infinity SELECT COUNT(*) FROM employees WHERE salary < BINARY_FLOAT_INFINITY; binary_double_nan A value of type BINARY_DOUBLE for which the condition IS NAN is true SELECT COUNT(*) FROM employees WHERE TO_BINARY_FLOAT(commission_pct) != BINARY_FLOAT_NAN; binary_double_ infinity Double-precision positive infinity SELECT COUNT(*) FROM employees WHERE salary < BINARY_FLOAT_INFINITY;
- 83. Literals Basic Elements of Oracle SQL 2-49 Datetime Literals Oracle Database supports four datetime datatypes: DATE, TIMESTAMP, TIMESTAMP WITH TIME ZONE, and TIMESTAMP WITH LOCAL TIME ZONE. Date Literals You can specify a DATE value as a string literal, or you can convert a character or numeric value to a date value with the TO_DATE function. DATE literals are the only case in which Oracle Database accepts a TO_DATE expression in place of a string literal. To specify a DATE value as a literal, you must use the Gregorian calendar. You can specify an ANSI literal, as shown in this example: DATE '1998-12-25' The ANSI date literal contains no time portion, and must be specified in exactly this format ('YYYY-MM-DD'). Alternatively you can specify an Oracle date value, as in the following example: TO_DATE('98-DEC-25 17:30','YY-MON-DD HH24:MI') The default date format for an Oracle DATE value is specified by the initialization parameter NLS_DATE_FORMAT. This example date format includes a two-digit number for the day of the month, an abbreviation of the month name, the last two digits of the year, and a 24-hour time designation. Oracle automatically converts character values that are in the default date format into date values when they are used in date expressions. If you specify a date value without a time component, then the default time is midnight (00:00:00 or 12:00:00 for 24-hour and 12-hour clock time, respectively). If you specify a date value without a date, then the default date is the first day of the current month. Oracle DATE columns always contain both the date and time fields. Therefore, if you query a DATE column, then you must either specify the time field in your query or ensure that the time fields in the DATE column are set to midnight. Otherwise, Oracle may not return the query results you expect. You can use the TRUNC (date) function to set the time field to midnight, or you can include a greater-than or less-than condition in the query instead of an equality or inequality condition. Here are some examples that assume a table my_table with a number column row_ num and a DATE column datecol: INSERT INTO my_table VALUES (1, SYSDATE); INSERT INTO my_table VALUES (2, TRUNC(SYSDATE)); SELECT * FROM my_table; ROW_NUM DATECOL ---------- --------- 1 03-OCT-02 2 03-OCT-02 SELECT * FROM my_table WHERE datecol = TO_DATE('03-OCT-02','DD-MON-YY'); ROW_NUM DATECOL ---------- --------- 2 03-OCT-02
- 84. Literals 2-50 Oracle Database SQL Reference SELECT * FROM my_table WHERE datecol > TO_DATE('02-OCT-02', 'DD-MON-YY'); ROW_NUM DATECOL ---------- --------- 1 03-OCT-02 2 03-OCT-02 If you know that the time fields of your DATE column are set to midnight, then you can query your DATE column as shown in the immediately preceding example, or by using the DATE literal: SELECT * FROM my_table WHERE datecol = DATE '2002-10-03'; However, if the DATE column contains values other than midnight, then you must filter out the time fields in the query to get the correct result. For example: SELECT * FROM my_table WHERE TRUNC(datecol) = DATE '2002-10-03'; Oracle applies the TRUNC function to each row in the query, so performance is better if you ensure the midnight value of the time fields in your data. To ensure that the time fields are set to midnight, use one of the following methods during inserts and updates: ■ Use the TO_DATE function to mask out the time fields: INSERT INTO my_table VALUES (3, TO_DATE('3-OCT-2002','DD-MON-YYYY')); ■ Use the DATE literal: INSERT INTO my_table VALUES (4, '03-OCT-02'); ■ Use the TRUNC function: INSERT INTO my_table VALUES (5, TRUNC(SYSDATE)); The date function SYSDATE returns the current system date and time. The function CURRENT_DATE returns the current session date. For information on SYSDATE, the TO_* datetime functions, and the default date format, see "Datetime Functions" on page 5-4. TIMESTAMP Literals The TIMESTAMP datatype stores year, month, day, hour, minute, and second, and fractional second values. When you specify TIMESTAMP as a literal, the fractional_seconds_precision value can be any number of digits up to 9, as follows: TIMESTAMP ’1997-01-31 09:26:50.124’ TIMESTAMP WITH TIME ZONE Literals The TIMESTAMP WITH TIME ZONE datatype is a variant of TIMESTAMP that includes a time zone offset. When you specify TIMESTAMP WITH TIME ZONE as a literal, the fractional_seconds_precision value can be any number of digits up to 9. For example: TIMESTAMP '1997-01-31 09:26:56.66 +02:00' Two TIMESTAMP WITH TIME ZONE values are considered identical if they represent the same instant in UTC, regardless of the TIME ZONE offsets stored in the data. For example, TIMESTAMP '1999-04-15 8:00:00 -8:00'
- 85. Literals Basic Elements of Oracle SQL 2-51 is the same as TIMESTAMP '1999-04-15 11:00:00 -5:00' That is, 8:00 a.m. Pacific Standard Time is the same as 11:00 a.m. Eastern Standard Time. You can replace the UTC offset with the TZR (time zone region) format element. For example, the following example has the same value as the preceding example: TIMESTAMP '1999-04-15 8:00:00 US/Pacific' To eliminate the ambiguity of boundary cases when the daylight saving time switches, use both the TZR and a corresponding TZD format element. The following example ensures that the preceding example will return a daylight saving time value: TIMESTAMP '1999-10-29 01:30:00 US/Pacific PDT' You can also express the time zone offset using a datetime expression: SELECT TIMESTAMP ’1999-10-29 01:30:00’ AT TIME ZONE ’US/Pacific’ FROM DUAL; If you do not add the TZD format element, and the datetime value is ambiguous, then Oracle returns an error if you have the ERROR_ON_OVERLAP_TIME session parameter set to TRUE. If that parameter is set to FALSE, then Oracle interprets the ambiguous datetime as standard time in the specified region. TIMESTAMP WITH LOCAL TIME ZONE Literals The TIMESTAMP WITH LOCAL TIME ZONE datatype differs from TIMESTAMP WITH TIME ZONE in that data stored in the database is normalized to the database time zone. The time zone offset is not stored as part of the column data. There is no literal for TIMESTAMP WITH LOCAL TIME ZONE. Rather, you represent values of this datatype using any of the other valid datetime literals. The table that follows shows some of the formats you can use to insert a value into a TIMESTAMP WITH LOCAL TIME ZONE column, along with the corresponding value returned by a query. Notice that if the value specified does not include a time component (either explicitly or implicitly, then the value returned defaults to midnight. Interval Literals An interval literal specifies a period of time. You can specify these differences in terms of years and months, or in terms of days, hours, minutes, and seconds. Oracle Database supports two types of interval literals, YEAR TO MONTH and DAY TO SECOND. See Also: "Datetime Expressions" on page 6-8 for more information Value Specified in INSERT Statement Value Returned by Query ’19-FEB-2004’ 19-FEB-2004.00.00.000000 AM SYSTIMESTAMP 19-FEB-04 02.54.36.497659 PM TO_TIMESTAMP(’19-FEB-2004’, ’DD-MON-YYYY’)); 19-FEB-04 12.00.00.000000 AM SYSDATE 19-FEB-04 02.55.29.000000 PM TO_DATE(’19-FEB-2004’, ’DD-MON-YYYY’)); 19-FEB-04 12.00.00.000000 AM TIMESTAMP’2004-02-19 8:00:00 US/Pacific’); 19-FEB-04 08.00.00.000000 AM
- 86. Literals 2-52 Oracle Database SQL Reference Each type contains a leading field and may contain a trailing field. The leading field defines the basic unit of date or time being measured. The trailing field defines the smallest increment of the basic unit being considered. For example, a YEAR TO MONTH interval considers an interval of years to the nearest month. A DAY TO MINUTE interval considers an interval of days to the nearest minute. If you have date data in numeric form, then you can use the NUMTOYMINTERVAL or NUMTODSINTERVAL conversion function to convert the numeric data into interval values. Interval literals are used primarily with analytic functions. INTERVAL YEAR TO MONTH Specify YEAR TO MONTH interval literals using the following syntax: interval_year_to_month::= where ■ 'integer [-integer]' specifies integer values for the leading and optional trailing field of the literal. If the leading field is YEAR and the trailing field is MONTH, then the range of integer values for the month field is 0 to 11. ■ precision is the maximum number of digits in the leading field. The valid range of the leading field precision is 0 to 9 and its default value is 2. Restriction on the Leading Field If you specify a trailing field, it must be less significant than the leading field. For example, INTERVAL '0-1' MONTH TO YEAR is not valid. The following INTERVAL YEAR TO MONTH literal indicates an interval of 123 years, 2 months: INTERVAL '123-2' YEAR(3) TO MONTH Examples of the other forms of the literal follow, including some abbreviated versions: See Also: "Analytic Functions" on page 5-9, NUMTODSINTERVAL on page 5-108, NUMTOYMINTERVAL on page 5-109, and Oracle Database Data Warehousing Guide Form of Interval Literal Interpretation INTERVAL '123-2' YEAR(3) TO MONTH An interval of 123 years, 2 months. You must specify the leading field precision if it is greater than the default of 2 digits. INTERVAL '123' YEAR(3) An interval of 123 years 0 months. INTERVAL '300' MONTH(3) An interval of 300 months. INTERVAL ’ integer – integer ’ YEAR MONTH ( precision ) TO YEAR MONTH
- 87. Literals Basic Elements of Oracle SQL 2-53 You can add or subtract one INTERVAL YEAR TO MONTH literal to or from another to yield another INTERVAL YEAR TO MONTH literal. For example: INTERVAL '5-3' YEAR TO MONTH + INTERVAL'20' MONTH = INTERVAL '6-11' YEAR TO MONTH INTERVAL DAY TO SECOND Specify DAY TO SECOND interval literals using the following syntax: interval_day_to_second::= where ■ integer specifies the number of days. If this value contains more digits than the number specified by the leading precision, then Oracle returns an error. ■ time_expr specifies a time in the format HH[:MI[:SS[.n]]] or MI[:SS[.n]] or SS[.n], where n specifies the fractional part of a second. If n contains more digits than the number specified by fractional_seconds_precision, then n is rounded to the number of digits specified by the fractional_seconds_ precision value. You can specify time_expr following an integer and a space only if the leading field is DAY. INTERVAL '4' YEAR Maps to INTERVAL '4-0' YEAR TO MONTH and indicates 4 years. INTERVAL '50' MONTH Maps to INTERVAL '4-2' YEAR TO MONTH and indicates 50 months or 4 years 2 months. INTERVAL '123' YEAR Returns an error, because the default precision is 2, and '123' has 3 digits. Form of Interval Literal Interpretation INTERVAL ’ integer integer time_expr time_expr ’ DAY HOUR MINUTE ( leading_precision ) SECOND ( leading_precision , fractional_seconds_precision ) TO DAY HOUR MINUTE SECOND ( fractional_seconds_precision )
- 88. Format Models 2-54 Oracle Database SQL Reference ■ leading_precision is the number of digits in the leading field. Accepted values are 0 to 9. The default is 2. ■ fractional_seconds_precision is the number of digits in the fractional part of the SECOND datetime field. Accepted values are 1 to 9. The default is 6. Restriction on the Leading Field: If you specify a trailing field, it must be less significant than the leading field. For example, INTERVAL MINUTE TO DAY is not valid. As a result of this restriction, if SECOND is the leading field, the interval literal cannot have any trailing field. The valid range of values for the trailing field are as follows: ■ HOUR: 0 to 23 ■ MINUTE: 0 to 59 ■ SECOND: 0 to 59.999999999 Examples of the various forms of INTERVAL DAY TO SECOND literals follow, including some abbreviated versions: You can add or subtract one DAY TO SECOND interval literal from another DAY TO SECOND literal. For example. INTERVAL'20' DAY - INTERVAL'240' HOUR = INTERVAL'10-0' DAY TO SECOND Format Models A format model is a character literal that describes the format of datetime or numeric data stored in a character string. A format model does not change the internal representation of the value in the database. When you convert a character string into a date or number, a format model determines how Oracle Database interprets the string. Form of Interval Literal Interpretation INTERVAL '4 5:12:10.222' DAY TO SECOND(3) 4 days, 5 hours, 12 minutes, 10 seconds, and 222 thousandths of a second. INTERVAL '4 5:12' DAY TO MINUTE 4 days, 5 hours and 12 minutes. INTERVAL '400 5' DAY(3) TO HOUR 400 days 5 hours. INTERVAL '400' DAY(3) 400 days. INTERVAL '11:12:10.2222222' HOUR TO SECOND(7) 11 hours, 12 minutes, and 10.2222222 seconds. INTERVAL '11:20' HOUR TO MINUTE 11 hours and 20 minutes. INTERVAL '10' HOUR 10 hours. INTERVAL '10:22' MINUTE TO SECOND 10 minutes 22 seconds. INTERVAL '10' MINUTE 10 minutes. INTERVAL '4' DAY 4 days. INTERVAL '25' HOUR 25 hours. INTERVAL '40' MINUTE 40 minutes. INTERVAL '120' HOUR(3) 120 hours. INTERVAL '30.12345' SECOND(2,4) 30.1235 seconds. The fractional second '12345' is rounded to '1235' because the precision is 4.
- 89. Format Models Basic Elements of Oracle SQL 2-55 In SQL statements, you can use a format model as an argument of the TO_CHAR and TO_DATE functions to specify: ■ The format for Oracle to use to return a value from the database ■ The format for a value you have specified for Oracle to store in the database For example: ■ The datetime format model for the string '17:45:29' is 'HH24:MI:SS'. ■ The datetime format model for the string '11-Nov-1999' is 'DD-Mon-YYYY'. ■ The number format model for the string '$2,304.25' is '$9,999.99'. For lists of number and datetime format model elements, see Table 2–17, " Matching Character Data and Format Models with the FX Format Model Modifier" on page 2-66 and Table 2–19, " Attributes of the XMLFormat Object" on page 2-68. The values of some formats are determined by the value of initialization parameters. For such formats, you can specify the characters returned by these format elements implicitly using the initialization parameter NLS_TERRITORY. You can change the default date format for your session with the ALTER SESSION statement. This remainder of this section describes how to use: ■ Number Format Models ■ Datetime Format Models ■ Format Model Modifiers Number Format Models You can use number format models in the following functions: ■ In the TO_CHAR function to translate a value of NUMBER, BINARY_FLOAT, or BINARY_DOUBLE datatype to VARCHAR2 datatype ■ In the TO_NUMBER function to translate a value of CHAR or VARCHAR2 datatype to NUMBER datatype ■ In the TO_BINARY_FLOAT and TO_BINARY_DOUBLE functions to translate CHAR and VARCHAR2 expressions to BINARY_FLOAT or BINARY_DOUBLE values All number format models cause the number to be rounded to the specified number of significant digits. If a value has more significant digits to the left of the decimal place than are specified in the format, then pound signs (#) replace the value. This event typically occurs when you are using TO_CHAR with a restrictive number format string, causing a rounding operation. ■ If a positive NUMBER value is extremely large and cannot be represented in the specified format, then the infinity sign (~) replaces the value. Likewise, if a See Also: ■ ALTER SESSION on page 11-45 for information on changing the values of these parameters and Format Model Examples on page 2-65 for examples of using format models ■ TO_CHAR (datetime) on page 5-191, TO_CHAR (number) on page 5-193, and TO_DATE on page 5-195 ■ Oracle Database Reference and Oracle Database Globalization Support Guide for information on these parameters
- 90. Format Models 2-56 Oracle Database SQL Reference negative NUMBER value is extremely small and cannot be represented by the specified format, then the negative infinity sign replaces the value (-~). ■ If a BINARY_FLOAT or BINARY_DOUBLE value is converted to CHAR or NCHAR, and the input is either infinity or NaN (not a number), then Oracle always returns the pound signs to replace the value. Number Format Elements A number format model is composed of one or more number format elements. The tables that follow list the elements of a number format model and provide some examples. Negative return values automatically contain a leading negative sign and positive values automatically contain a leading space unless the format model contains the MI, S, or PR format element. Table 2–13 Number Format Elements Element Example Description , (comma) 9,999 Returns a comma in the specified position. You can specify multiple commas in a number format model. Restrictions: ■ A comma element cannot begin a number format model. ■ A comma cannot appear to the right of a decimal character or period in a number format model. . (period) 99.99 Returns a decimal point, which is a period (.) in the specified position. Restriction: You can specify only one period in a number format model. $ $9999 Returns value with a leading dollar sign. 0 0999 9990 Returns leading zeros. Returns trailing zeros. 9 9999 Returns value with the specified number of digits with a leading space if positive or with a leading minus if negative. Leading zeros are blank, except for a zero value, which returns a zero for the integer part of the fixed-point number. B B9999 Returns blanks for the integer part of a fixed-point number when the integer part is zero (regardless of zeros in the format model). C C999 Returns in the specified position the ISO currency symbol (the current value of the NLS_ISO_CURRENCY parameter). D 99D99 Returns in the specified position the decimal character, which is the current value of the NLS_NUMERIC_CHARACTER parameter. The default is a period (.). Restriction: You can specify only one decimal character in a number format model. EEEE 9.9EEEE Returns a value using in scientific notation. G 9G999 Returns in the specified position the group separator (the current value of the NLS_NUMERIC_CHARACTER parameter). You can specify multiple group separators in a number format model. Restriction: A group separator cannot appear to the right of a decimal character or period in a number format model. L L999 Returns in the specified position the local currency symbol (the current value of the NLS_CURRENCY parameter).
- 91. Format Models Basic Elements of Oracle SQL 2-57 Table 2–14 shows the results of the following query for different values of number and 'fmt': SELECT TO_CHAR(number, 'fmt') FROM DUAL; MI 9999MI Returns negative value with a trailing minus sign (-). Returns positive value with a trailing blank. Restriction: The MI format element can appear only in the last position of a number format model. PR 9999PR Returns negative value in <angle brackets>. Returns positive value with a leading and trailing blank. Restriction: The PR format element can appear only in the last position of a number format model. RN rn RN rn Returns a value as Roman numerals in uppercase. Returns a value as Roman numerals in lowercase. Value can be an integer between 1 and 3999. S S9999 9999S Returns negative value with a leading minus sign (-). Returns positive value with a leading plus sign (+). Returns negative value with a trailing minus sign (-). Returns positive value with a trailing plus sign (+). Restriction: The S format element can appear only in the first or last position of a number format model. TM TM The text minimum number format model returns (in decimal output) the smallest number of characters possible. This element is case insensitive. The default is TM9, which returns the number in fixed notation unless the output exceeds 64 characters. If the output exceeds 64 characters, then Oracle Database automatically returns the number in scientific notation. Restrictions: ■ You cannot precede this element with any other element. ■ You can follow this element only with one 9 or one E (or e), but not with any combination of these. The following statement returns an error: ■ SELECT TO_CHAR(1234, ’TM9e’) FROM DUAL; U U9999 Returns in the specified position the Euro (or other) dual currency symbol (the current value of the NLS_DUAL_CURRENCY parameter). V 999V99 Returns a value multiplied by 10n (and if necessary, round it up), where n is the number of 9’s after the V. X XXXX xxxx Returns the hexadecimal value of the specified number of digits. If the specified number is not an integer, then Oracle Database rounds it to an integer. Restrictions: ■ This element accepts only positive values or 0. Negative values return an error. ■ You can precede this element only with 0 (which returns leading zeroes) or FM. Any other elements return an error. If you specify neither 0 nor FM with X, then the return always has 1 leading blank. Table 2–13 (Cont.) Number Format Elements Element Example Description
- 92. Format Models 2-58 Oracle Database SQL Reference Datetime Format Models You can use datetime format models in the following functions: ■ In the TO_* datetime functions to translate a character value that is in a format other than the default format into a datetime value. (The TO_* datetime functions are TO_CHAR, TO_DATE, TO_TIMESTAMP, TO_TIMESTAMP_TZ, TO_YMINTERVAL, and TO_DSINTERVAL.) ■ In the TO_CHAR function to translate a datetime value that is in a format other than the default format into a string (for example, to print the date from an application) The total length of a datetime format model cannot exceed 22 characters. The default datetime formats are specified either explicitly with the initialization parameter NLS_DATE_FORMAT or implicitly with the initialization parameter NLS_ TERRITORY. You can change the default datetime formats for your session with the ALTER SESSION statement. Table 2–14 Results of Number Conversions number 'fmt' Result -1234567890 9999999999S '1234567890-' 0 99.99 ' .00' +0.1 99.99 ' .10' -0.2 99.99 ' -.20' 0 90.99 ' 0.00' +0.1 90.99 ' 0.10' -0.2 90.99 ' -0.20' 0 9999 ' 0' 1 9999 ' 1' 0 B9999 ' ' 1 B9999 ' 1' 0 B90.99 ' ' +123.456 999.999 ' 123.456' -123.456 999.999 '-123.456' +123.456 FM999.009 '123.456' +123.456 9.9EEEE ' 1.2E+02' +1E+123 9.9EEEE ' 1.0E+123' +123.456 FM9.9EEEE '1.2E+02' +123.45 FM999.009 '123.45' +123.0 FM999.009 '123.00' +123.45 L999.99 ' $123.45' +123.45 FML999.99 '$123.45' +1234567890 9999999999S '1234567890+' See Also: ALTER SESSION on page 11-45 and Oracle Database Globalization Support Guide for information on the NLS parameters
- 93. Format Models Basic Elements of Oracle SQL 2-59 Datetime Format Elements A datetime format model is composed of one or more datetime format elements as listed in Table 2–19, " Attributes of the XMLFormat Object" on page 2-68. ■ For input format models, format items cannot appear twice, and format items that represent similar information cannot be combined. For example, you cannot use 'SYYYY' and 'BC' in the same format string. ■ Some of the datetime format elements cannot be used in the TO_* datetime functions, as noted in Table 2–19. ■ The following datetime format elements can be used in timestamp and interval format models, but not in the original DATE format model: FF, TZD, TZH, TZM, and TZR. ■ Many datetime format elements are blank padded to a specific length. Please refer to the format model modifier FM on page 2-64 for more information. Uppercase Letters in Date Format Elements Capitalization in a spelled-out word, abbreviation, or Roman numeral follows capitalization in the corresponding format element. For example, the date format model 'DAY' produces capitalized words like 'MONDAY'; 'Day' produces 'Monday'; and 'day' produces 'monday'. Punctuation and Character Literals in Datetime Format Models You can include these characters in a date format model: ■ Punctuation such as hyphens, slashes, commas, periods, and colons ■ Character literals, enclosed in double quotation marks These characters appear in the return value in the same location as they appear in the format model. Table 2–15 Datetime Format Elements Element Specify in TO_* datetime functions? Description - / , . ; : "text" Yes Punctuation and quoted text is reproduced in the result. AD A.D. Yes AD indicator with or without periods. AM A.M. Yes Meridian indicator with or without periods. BC B.C. Yes BC indicator with or without periods. CC SCC No Century. ■ If the last 2 digits of a 4-digit year are between 01 and 99 (inclusive), then the century is one greater than the first 2 digits of that year. ■ If the last 2 digits of a 4-digit year are 00, then the century is the same as the first 2 digits of that year. For example, 2002 returns 21; 2000 returns 20.
- 94. Format Models 2-60 Oracle Database SQL Reference D Yes Day of week (1-7). DAY Yes Name of day, padded with blanks to display width of the widest name of day in the date language used for this element. DD Yes Day of month (1-31). DDD Yes Day of year (1-366). DL Yes Returns a value in the long date format, which is an extension of Oracle Database’s DATE format (the current value of the NLS_DATE_FORMAT parameter). Makes the appearance of the date components (day name, month number, and so forth) depend on the NLS_TERRITORY and NLS_LANGUAGE parameters. For example, in the AMERICAN_AMERICA locale, this is equivalent to specifying the format ’fmDay, Month dd, yyyy’. In the GERMAN_GERMANY locale, it is equivalent to specifying the format ’fmDay, dd. Month yyyy’. Restriction: You can specify this format only with the TS element, separated by white space. DS Yes Returns a value in the short date format. Makes the appearance of the date components (day name, month number, and so forth) depend on the NLS_ TERRITORY and NLS_LANGUAGE parameters. For example, in the AMERICAN_ AMERICA locale, this is equivalent to specifying the format ’MM/DD/RRRR’. In the ENGLISH_UNITED_KINGDOM locale, it is equivalent to specifying the format ’DD/MM/RRRR’. Restriction: You can specify this format only with the TS element, separated by white space. DY Yes Abbreviated name of day. E No Abbreviated era name (Japanese Imperial, ROC Official, and Thai Buddha calendars). EE No Full era name (Japanese Imperial, ROC Official, and Thai Buddha calendars). FF [1..9] Yes Fractional seconds; no radix character is printed (use the X format element to add the radix character). Use the numbers 1 to 9 after FF to specify the number of digits in the fractional second portion of the datetime value returned. If you do not specify a digit, then Oracle Database uses the precision specified for the datetime datatype or the datatype’s default precision. Examples: ’HH:MI:SS.FF’ SELECT TO_CHAR(SYSTIMESTAMP, ’SS.FF3’) from dual; FM Yes Returns a value with no leading or trailing blanks. See Also: Additional discussion on this format model modifier in the Oracle Database SQL Reference FX Yes Requires exact matching between the character data and the format model. See Also: Additional discussion on this format model modifier in the Oracle Database SQL Reference HH Yes Hour of day (1-12). HH12 No Hour of day (1-12). HH24 Yes Hour of day (0-23). IW No Week of year (1-52 or 1-53) based on the ISO standard. IYY IY I No Last 3, 2, or 1 digit(s) of ISO year. Table 2–15 (Cont.) Datetime Format Elements Element Specify in TO_* datetime functions? Description
- 95. Format Models Basic Elements of Oracle SQL 2-61 IYYY No 4-digit year based on the ISO standard. J Yes Julian day; the number of days since January 1, 4712 BC. Number specified with J must be integers. MI Yes Minute (0-59). MM Yes Month (01-12; January = 01). MON Yes Abbreviated name of month. MONTH Yes Name of month, padded with blanks to display width of the widest name of month in the date language used for this element. PM P.M. No Meridian indicator with or without periods. Q No Quarter of year (1, 2, 3, 4; January - March = 1). RM Yes Roman numeral month (I-XII; January = I). RR Yes Lets you store 20th century dates in the 21st century using only two digits. See Also: Additional discussion on RR datetime format element in the Oracle Database SQL Reference RRRR Yes Round year. Accepts either 4-digit or 2-digit input. If 2-digit, provides the same return as RR. If you do not want this functionality, then enter the 4-digit year. SS Yes Second (0-59). SSSSS Yes Seconds past midnight (0-86399). TS Yes Returns a value in the short time format. Makes the appearance of the time components (hour, minutes, and so forth) depend on the NLS_TERRITORY and NLS_LANGUAGE initialization parameters. Restriction: You can specify this format only with the DL or DS element, separated by white space. TZD Yes Daylight savings information. The TZD value is an abbreviated time zone string with daylight savings information. It must correspond with the region specified in TZR. Example: PST (for US/Pacific standard time); PDT (for US/Pacific daylight time). TZH Yes Time zone hour. (See TZM format element.) Example: ’HH:MI:SS.FFTZH:TZM’. TZM Yes Time zone minute. (See TZH format element.) Example: ’HH:MI:SS.FFTZH:TZM’. TZR Yes Time zone region information. The value must be one of the time zone regions supported in the database. Example: US/Pacific WW No Week of year (1-53) where week 1 starts on the first day of the year and continues to the seventh day of the year. W No Week of month (1-5) where week 1 starts on the first day of the month and ends on the seventh. X Yes Local radix character. Example: ’HH:MI:SSXFF’. Y,YYY Yes Year with comma in this position. Table 2–15 (Cont.) Datetime Format Elements Element Specify in TO_* datetime functions? Description
- 96. Format Models 2-62 Oracle Database SQL Reference Oracle returns an error if an alphanumeric character is found in the date string where a punctuation character is found in the format string. For example, the following format string returns an error: TO_CHAR (TO_DATE('0297','MM/YY'), 'MM/YY') Datetime Format Elements and Globalization Support The functionality of some datetime format elements depends on the country and language in which you are using Oracle Database. For example, these datetime format elements return spelled values: ■ MONTH ■ MON ■ DAY ■ DY ■ BC or AD or B.C. or A.D. ■ AM or PM or A.M or P.M. The language in which these values are returned is specified either explicitly with the initialization parameter NLS_DATE_LANGUAGE or implicitly with the initialization parameter NLS_LANGUAGE. The values returned by the YEAR and SYEAR datetime format elements are always in English. The datetime format element D returns the number of the day of the week (1-7). The day of the week that is numbered 1 is specified implicitly by the initialization parameter NLS_TERRITORY. ISO Standard Date Format Elements Oracle calculates the values returned by the datetime format elements IYYY, IYY, IY, I, and IW according to the ISO standard. For information on the differences between these values and those returned by the datetime format elements YYYY, YYY, YY, Y, and WW, see the discussion of globalization support in Oracle Database Globalization Support Guide. YEAR SYEAR No Year, spelled out; S prefixes BC dates with a minus sign (-). YYYY SYYYY Yes 4-digit year; S prefixes BC dates with a minus sign. YYY YY Y Yes Last 3, 2, or 1 digit(s) of year. See Also: Oracle Database Reference and Oracle Database Globalization Support Guide for information on globalization support initialization parameters Table 2–15 (Cont.) Datetime Format Elements Element Specify in TO_* datetime functions? Description
- 97. Format Models Basic Elements of Oracle SQL 2-63 The RR Datetime Format Element The RR datetime format element is similar to the YY datetime format element, but it provides additional flexibility for storing date values in other centuries. The RR datetime format element lets you store 20th century dates in the 21st century by specifying only the last two digits of the year. If you use the TO_DATE function with the YY datetime format element, then the year returned always has the same first 2 digits as the current year. If you use the RR datetime format element instead, then the century of the return value varies according to the specified two-digit year and the last two digits of the current year. That is: ■ If the specified two-digit year is 00 to 49, then – If the last two digits of the current year are 00 to 49, then the returned year has the same first two digits as the current year. – If the last two digits of the current year are 50 to 99, then the first 2 digits of the returned year are 1 greater than the first 2 digits of the current year. ■ If the specified two-digit year is 50 to 99, then – If the last two digits of the current year are 00 to 49, then the first 2 digits of the returned year are 1 less than the first 2 digits of the current year. – If the last two digits of the current year are 50 to 99, then the returned year has the same first two digits as the current year. The following examples demonstrate the behavior of the RR datetime format element. RR Datetime Format Examples Assume these queries are issued between 1950 and 1999: SELECT TO_CHAR(TO_DATE('27-OCT-98', 'DD-MON-RR') ,'YYYY') "Year" FROM DUAL; Year ---- 1998 SELECT TO_CHAR(TO_DATE('27-OCT-17', 'DD-MON-RR') ,'YYYY') "Year" FROM DUAL; Year ---- 2017 Now assume these queries are issued between 2000 and 2049: SELECT TO_CHAR(TO_DATE('27-OCT-98', 'DD-MON-RR') ,'YYYY') "Year" FROM DUAL; Year ---- 1998 SELECT TO_CHAR(TO_DATE('27-OCT-17', 'DD-MON-RR') ,'YYYY') "Year" FROM DUAL; Year ----
- 98. Format Models 2-64 Oracle Database SQL Reference 2017 Note that the queries return the same values regardless of whether they are issued before or after the year 2000. The RR datetime format element lets you write SQL statements that will return the same values from years whose first two digits are different. Datetime Format Element Suffixes Table 2–16 lists suffixes that can be added to datetime format elements: Notes on date format element suffixes: ■ When you add one of these suffixes to a datetime format element, the return value is always in English. ■ Datetime suffixes are valid only to format output. You cannot use them to insert a date into the database. Format Model Modifiers The FM and FX modifiers, used in format models in the TO_CHAR function, control blank padding and exact format checking. A modifier can appear in a format model more than once. In such a case, each subsequent occurrence toggles the effects of the modifier. Its effects are enabled for the portion of the model following its first occurrence, and then disabled for the portion following its second, and then reenabled for the portion following its third, and so on. FM Fill mode. Oracle uses blank characters to fill format elements to a constant width equal to the largest element for the relevant format model in the current session language. For example, when NLS_LANGUAGE is AMERICAN, the largest element for MONTH is SEPTEMBER, so all values of the MONTH format element are padded to 9 display characters. This modifier suppresses blank padding in the return value of the TO_CHAR function: ■ In a datetime format element of a TO_CHAR function, this modifier suppresses blanks in subsequent character elements (such as MONTH) and suppresses leading zeroes for subsequent number elements (such as MI) in a date format model. Without FM, the result of a character element is always right padded with blanks to a fixed length, and leading zeroes are always returned for a number element. With FM, which suppresses blank padding, the length of the return value may vary. ■ In a number format element of a TO_CHAR function, this modifier suppresses blanks added to the left of the number, so that the result is left-justified in the output buffer. Without FM, the result is always right-justified in the buffer, resulting in blank-padding to the left of the number. FX Format exact. This modifier specifies exact matching for the character argument and datetime format model of a TO_DATE function: Table 2–16 Date Format Element Suffixes Suffix Meaning Example Element Example Value TH Ordinal Number DDTH 4TH SP Spelled Number DDSP FOUR SPTH or THSP Spelled, ordinal number DDSPTH FOURTH
- 99. Format Models Basic Elements of Oracle SQL 2-65 ■ Punctuation and quoted text in the character argument must exactly match (except for case) the corresponding parts of the format model. ■ The character argument cannot have extra blanks. Without FX, Oracle ignores extra blanks. ■ Numeric data in the character argument must have the same number of digits as the corresponding element in the format model. Without FX, numbers in the character argument can omit leading zeroes. When FX is enabled, you can disable this check for leading zeroes by using the FM modifier as well. If any portion of the character argument violates any of these conditions, then Oracle returns an error message. Format Model Examples The following statement uses a date format model to return a character expression: SELECT TO_CHAR(SYSDATE, 'fmDDTH')||' of '||TO_CHAR (SYSDATE, 'fmMonth')||', '||TO_CHAR(SYSDATE, 'YYYY') "Ides" FROM DUAL; Ides ------------------ 3RD of April, 1998 The preceding statement also uses the FM modifier. If FM is omitted, then the month is blank-padded to nine characters: SELECT TO_CHAR(SYSDATE, 'DDTH')||' of '|| TO_CHAR(SYSDATE, 'Month')||', '|| TO_CHAR(SYSDATE, 'YYYY') "Ides" FROM DUAL; Ides ----------------------- 03RD of April , 1998 The following statement places a single quotation mark in the return value by using a date format model that includes two consecutive single quotation marks: SELECT TO_CHAR(SYSDATE, 'fmDay')||'''s Special' "Menu" FROM DUAL; Menu ----------------- Tuesday's Special Two consecutive single quotation marks can be used for the same purpose within a character literal in a format model. Table 2–17 shows whether the following statement meets the matching conditions for different values of char and 'fmt' using FX (the table named table has a column date_column of datatype DATE): UPDATE table SET date_column = TO_DATE(char, 'fmt');
- 100. Format Models 2-66 Oracle Database SQL Reference Format of Return Values: Examples You can use a format model to specify the format for Oracle to use to return values from the database to you. The following statement selects the salaries of the employees in Department 80 and uses the TO_CHAR function to convert these salaries into character values with the format specified by the number format model '$99,990.99' SELECT last_name employee, TO_CHAR(salary, '$99,990.99') FROM employees WHERE department_id = 80; Because of this format model, Oracle returns salaries with leading dollar signs, commas every three digits, and two decimal places. The following statement selects the date on which each employee from Department 20 was hired and uses the TO_CHAR function to convert these dates to character strings with the format specified by the date format model 'fmMonth DD, YYYY': SELECT last_name employee, TO_CHAR(hire_date,'fmMonth DD, YYYY') hiredate FROM employees WHERE department_id = 20; With this format model, Oracle returns the hire dates without blank padding (as specified by fm), two digits for the day, and the century included in the year. Supplying the Correct Format Model: Examples When you insert or update a column value, the datatype of the value that you specify must correspond to the column datatype of the column. You can use format models to specify the format of a value that you are converting from one datatype to another datatype required for a column. For example, a value that you insert into a DATE column must be a value of the DATE datatype or a character string in the default date format (Oracle implicitly converts character strings in the default date format to the DATE datatype). If the value is in another format, then you must use the TO_DATE function to convert the value to the DATE datatype. You must also use a format model to specify the format of the character string. Table 2–17 Matching Character Data and Format Models with the FX Format Model Modifier char 'fmt' Match or Error? '15/ JAN /1998' 'DD-MON-YYYY' Match ' 15! JAN % /1998' 'DD-MON-YYYY' Error '15/JAN/1998' 'FXDD-MON-YYYY' Error '15-JAN-1998' 'FXDD-MON-YYYY' Match '1-JAN-1998' 'FXDD-MON-YYYY' Error '01-JAN-1998' 'FXDD-MON-YYYY' Match '1-JAN-1998' 'FXFMDD-MON-YYYY' Match See Also: "Format Model Modifiers" on page 2-64 for a description of the fm format element
- 101. Format Models Basic Elements of Oracle SQL 2-67 The following statement updates Hunold's hire date using the TO_DATE function with the format mask 'YYYY MM DD' to convert the character string '1998 05 20' to a DATE value: UPDATE employees SET hire_date = TO_DATE('1998 05 20','YYYY MM DD') WHERE last_name = 'Hunold'; String-to-Date Conversion Rules The following additional formatting rules apply when converting string values to date values (unless you have used the FX or FXFM modifiers in the format model to control exact format checking): ■ You can omit punctuation included in the format string from the date string if all the digits of the numerical format elements, including leading zeros, are specified. In other words, specify 02 and not 2 for two-digit format elements such as MM, DD, and YY. ■ You can omit time fields found at the end of a format string from the date string. ■ If a match fails between a datetime format element and the corresponding characters in the date string, then Oracle attempts alternative format elements, as shown in Table 2–18. XML Format Model The SYS_XMLGEN function returns an instance of type XMLType containing an XML document. Oracle provides the XMLFormat object, which lets you format the output of the SYS_XMLGEN function. Table 2–19 lists and describes the attributes of the XMLFormat object. The function that implements this type follows the table. Table 2–18 Oracle Format Matching Original Format Element Additional Format Elements to Try in Place of the Original 'MM' 'MON' and 'MONTH' 'MON 'MONTH' 'MONTH' 'MON' 'YY' 'YYYY' 'RR' 'RRRR' See Also: ■ SYS_XMLGEN on page 5-185 for information on the SYS_XMLGEN function ■ Oracle XML Developer's Kit Programmer's Guide for more information on the implementation of the XMLFormat object and its use
- 102. Nulls 2-68 Oracle Database SQL Reference The function that implements the XMLFormat object follows: STATIC FUNCTION createFormat( enclTag IN varchar2 := 'ROWSET', schemaType IN varchar2 := 'NO_SCHEMA', schemaName IN varchar2 := null, targetNameSpace IN varchar2 := null, dburlPrefix IN varchar2 := null, processingIns IN varchar2 := null) RETURN XMLGenFormatType deterministic parallel_enable, MEMBER PROCEDURE genSchema (spec IN varchar2), MEMBER PROCEDURE setSchemaName(schemaName IN varchar2), MEMBER PROCEDURE setTargetNameSpace(targetNameSpace IN varchar2), MEMBER PROCEDURE setEnclosingElementName(enclTag IN varchar2), MEMBER PROCEDURE setDbUrlPrefix(prefix IN varchar2), MEMBER PROCEDURE setProcessingIns(pi IN varchar2), CONSTRUCTOR FUNCTION XMLGenFormatType ( enclTag IN varchar2 := 'ROWSET', schemaType IN varchar2 := 'NO_SCHEMA', schemaName IN varchar2 := null, targetNameSpace IN varchar2 := null, dbUrlPrefix IN varchar2 := null, processingIns IN varchar2 := null) RETURN SELF AS RESULT deterministic parallel_enable . . . Nulls If a column in a row has no value, then the column is said to be null, or to contain null. Nulls can appear in columns of any datatype that are not restricted by NOT NULL or PRIMARY KEY integrity constraints. Use a null when the actual value is not known or when a value would not be meaningful. Do not use null to represent a value of zero, because they are not equivalent. Table 2–19 Attributes of the XMLFormat Object Attribute Datatype Purpose enclTag VARCHAR2(100) The name of the enclosing tag for the result of the SYS_XMLGEN function. If the input to the function is a column name, the default is the column name. Otherwise the default is ROW. When schemaType is set to USE_GIVEN_SCHEMA, this attribute also gives the name of the XMLSchema element. schemaType VARCHAR2(100) The type of schema generation for the output document. Valid values are 'NO_SCHEMA' and 'USE_GIVEN_SCHEMA'. The default is 'NO_ SCHEMA'. schemaName VARCHAR2(4000) The name of the target schema Oracle uses if the value of the schemaType is 'USE_GIVEN_SCHEMA'. If you specify schemaName, then Oracle uses the enclosing tag as the element name. targetNameSpace VARCHAR2(4000) The target namespace if the schema is specified (that is, schemaType is GEN_SCHEMA_*, or USE_GIVEN_SCHEMA) dburl VARCHAR2(2000) The URL to the database to use if WITH_SCHEMA is specified. If this attribute is not specified, then Oracle declares the URL to the types as a relative URL reference. processingIns VARCHAR2(4000) User-provided processing instructions, which are appended to the top of the function output before the element.
- 103. Nulls Basic Elements of Oracle SQL 2-69 Any arithmetic expression containing a null always evaluates to null. For example, null added to 10 is null. In fact, all operators (except concatenation) return null when given a null operand. Nulls in SQL Functions All scalar functions (except REPLACE, NVL, and CONCAT) return null when given a null argument. You can use the NVL function to return a value when a null occurs. For example, the expression NVL(commission_pct,0) returns 0 if commission_pct is null or the value of commission_pct if it is not null. Most aggregate functions ignore nulls. For example, consider a query that averages the five values 1000, null, null, null, and 2000. Such a query ignores the nulls and calculates the average to be (1000+2000)/2 = 1500. Nulls with Comparison Conditions To test for nulls, use only the comparison conditions IS NULL and IS NOT NULL. If you use any other condition with nulls and the result depends on the value of the null, then the result is UNKNOWN. Because null represents a lack of data, a null cannot be equal or unequal to any value or to another null. However, Oracle considers two nulls to be equal when evaluating a DECODE function. Please refer to DECODE on page 5-51 for syntax and additional information. Oracle also considers two nulls to be equal if they appear in compound keys. That is, Oracle considers identical two compound keys containing nulls if all the non-null components of the keys are equal. Nulls in Conditions A condition that evaluates to UNKNOWN acts almost like FALSE. For example, a SELECT statement with a condition in the WHERE clause that evaluates to UNKNOWN returns no rows. However, a condition evaluating to UNKNOWN differs from FALSE in that further operations on an UNKNOWN condition evaluation will evaluate to UNKNOWN. Thus, NOT FALSE evaluates to TRUE, but NOT UNKNOWN evaluates to UNKNOWN. Table 2–20 shows examples of various evaluations involving nulls in conditions. If the conditions evaluating to UNKNOWN were used in a WHERE clause of a SELECT statement, then no rows would be returned for that query. Note: Oracle Database currently treats a character value with a length of zero as null. However, this may not continue to be true in future releases, and Oracle recommends that you do not treat empty strings the same as nulls.
- 104. Comments 2-70 Oracle Database SQL Reference For the truth tables showing the results of logical conditions containing nulls, see Table 7–5 on page 7-8, Table 7–6 on page 7-8, and Table 7–7 on page 7-8. Comments You can associate comments with SQL statements and schema objects. Comments Within SQL Statements Comments can make your application easier for you to read and maintain. For example, you can include a comment in a statement that describes the purpose of the statement within your application. With the exception of hints, comments within SQL statements do not affect the statement execution. Please refer to "Using Hints" on page 2-71 on using this particular form of comment. A comment can appear between any keywords, parameters, or punctuation marks in a statement. You can include a comment in a statement in two ways: ■ Begin the comment with a slash and an asterisk (/*). Proceed with the text of the comment. This text can span multiple lines. End the comment with an asterisk and a slash (*/). The opening and terminating characters need not be separated from the text by a space or a line break. ■ Begin the comment with -- (two hyphens). Proceed with the text of the comment. This text cannot extend to a new line. End the comment with a line break. Some of the tools used to enter SQL have additional restrictions. For example, if you are using SQL*Plus, by default you cannot have a blank line inside a multiline comment. For more information, please refer to the documentation for the tool you use as an interface to the database. A SQL statement can contain multiple comments of both styles. The text of a comment can contain any printable characters in your database character set. Example These statements contain many comments: SELECT last_name, salary + NVL(commission_pct, 0), job_id, e.department_id /* Select all employees whose compensation is greater than that of Pataballa.*/ Table 2–20 Conditions Containing Nulls Condition Value of A Evaluation a IS NULL 10 FALSE a IS NOT NULL 10 TRUE a IS NULL NULL TRUE a IS NOT NULL NULL FALSE a = NULL 10 UNKNOWN a != NULL 10 UNKNOWN a = NULL NULL UNKNOWN a != NULL NULL UNKNOWN a = 10 NULL UNKNOWN a != 10 NULL UNKNOWN
- 105. Comments Basic Elements of Oracle SQL 2-71 FROM employees e, departments d /*The DEPARTMENTS table is used to get the department name.*/ WHERE e.department_id = d.department_id AND salary + NVL(commission_pct,0) > /* Subquery: */ (SELECT salary + NVL(commission_pct,0) /* total compensation is salar + commission_pct */ FROM employees WHERE last_name = 'Pataballa'); SELECT last_name, -- select the name salary + NVL(commission_pct, 0),-- total compensation job_id, -- job e.department_id -- and department FROM employees e, -- of all employees departments d WHERE e.department_id = d.department_id AND salary + NVL(commission_pct, 0) > -- whose compensation -- is greater than (SELECT salary + NVL(commission_pct,0) -- the compensation FROM employees WHERE last_name = 'Pataballa') -- of Pataballa. ; Comments on Schema Objects You can associate a comment with a table, view, materialized view, or column using the COMMENT command. Comments associated with schema objects are stored in the data dictionary. Please refer to COMMENT on page 13-57 for a description of comments. Using Hints You can use comments in a SQL statement to pass instructions, or hints, to the Oracle Database optimizer. The optimizer uses these hints to choose an execution plan for the statement, unless some condition exists that prevents the optimizer from doing so. A statement block can have only one comment containing hints, and that comment must follow the SELECT, UPDATE, INSERT, MERGE, or DELETE keyword. Only two hints are used with INSERT statements: The APPEND hint always follows the INSERT keyword, and the PARALLEL hint can follow the INSERT keyword. The following syntax diagram shows hints contained in both styles of comments that Oracle supports within a statement block. The hint syntax must follow immediately after an INSERT, UPDATE, DELETE, SELECT, or MERGE keyword that begins the statement block. Note: Hints should be used sparingly, and only after you have collected statistics on the relevant tables and evaluated the optimizer plan without hints using the EXPLAIN PLAN statement. Changing database conditions as well as query performance enhancements in subsequent releases can have significant impact on how hints in your code affect performance.
- 106. Comments 2-72 Oracle Database SQL Reference hint::= where: ■ The plus sign (+) causes Oracle to interpret the comment as a list of hints. The plus sign must follow immediately after the comment delimiter. No space is permitted. ■ hint is one of the hints discussed in this section. The space between the plus sign and the hint is optional. If the comment contains multiple hints, then separate the hints by at least one space. ■ string is other commenting text that can be interspersed with the hints. The --+ syntax requires that the entire comment be on a single line. Oracle Database ignores hints and does not return an error under the following circumstances: ■ The hint contains misspellings or syntax errors. However, the database does consider other correctly specified hints in the same comment. ■ The comment containing the hint does not follow a DELETE, INSERT, MERGE, SELECT, or UPDATE keyword. ■ A combination of hints conflict with each other. However, the database does consider other hints in the same comment. ■ The database environment uses PL/SQL version 1, such as Forms version 3 triggers, Oracle Forms 4.5, and Oracle Reports 2.5. Many hints can apply both to specific tables or indexes and more globally to tables within a view or to columns that are part of indexes. The syntactic elements tablespec and indexspec define these global hints. tablespec::= You must specify the table to be accessed exactly as it appears in the statement. If the statement uses an alias for the table, then use the alias rather than the table name in the hint. However, do not include the schema name with the table name within the hint, even if the schema name appears in the statement. See Also: Oracle Database Performance Tuning Guide for information on the following topics: ■ When to use global hints and how Oracle interprets them ■ Using EXPLAIN PLAN to learn how the optimizer is executing a query ■ References in hints to tables within views /*+ hint string */ – – + hint string view . table
- 107. Comments Basic Elements of Oracle SQL 2-73 indexspec::= When tablespec is followed by indexspec in the specification of a hint, a comma separating the table name and index name is permitted but not required. Commas are also permitted, but not required, to separate multiple occurrences of indexspec. Specifying a Query Block in a Hint You can specify an optional query block name in many hints to specify the query block to which the hint applies. This syntax lets you specify in the outer query a hint that applies to an inline view. When you specify a hint in the query block itself to which the hint applies, you omit the @queryblock syntax. The syntax of the query block argument is of the form @queryblock, where queryblock is an identifier that specifies a query block in the query. The queryblock identifier can either be system-generated or user-specified. ■ The system-generated identifier can be obtained by using EXPLAIN PLAN for the query. Pretransformation query block names can be determined by running EXPLAIN PLAN for the query using the NO_QUERY_TRANSFORMATION hint. See "NO_QUERY_TRANSFORMATION Hint" on page 2-88. ■ The user-specified name can be set with the QB_NAME hint. See "QB_NAME Hint" on page 2-93. Table 2–21 lists the hints by functional category and contains cross-references to the syntax and semantics for each hint. An alphabetical listing of the hints follows the table. See Also: Oracle Database Performance Tuning Guide for information on: ■ using hints to optimize SQL statements and on detailed information about using the tablespec and indexspec syntax ■ specifying a query block in a hint ■ descriptions of hint categories and when to use them Table 2–21 Hints by Functional Category Hint Link to Syntax and Semantics Optimization Goals and Approaches ALL_ROWS Hint on page 2-75 FIRST_ROWS Hint on page 2-78 -- RULE Hint on page 2-94 Access Path Hints CLUSTER Hint on page 2-76 -- FULL Hint on page 2-78 -- HASH Hint on page 2-79 -- INDEX Hint on page 2-79 NO_INDEX Hint on page 2-85 index ( table . column )
- 108. Comments 2-74 Oracle Database SQL Reference -- INDEX_ASC Hint on page 2-80 INDEX_DESC Hint on page 2-80 -- INDEX_COMBINE Hint on page 2-80 -- INDEX_JOIN Hint on page 2-81 -- INDEX_FFS Hint on page 2-81 -- INDEX_SS Hint on page 2-81 -- INDEX_SS_ASC Hint on page 2-82 -- INDEX_SS_DESC Hint on page 2-82 -- NO_INDEX_FFS Hint on page 2-85 -- NO_INDEX_SS Hint on page 2-86 Join Order Hints ORDERED Hint on page 2-90 -- LEADING Hint on page 2-83 Join Operation Hints USE_HASH Hint on page 2-96 NO_USE_HASH Hint on page 2-89 -- USE_MERGE Hint on page 2-96 NO_USE_MERGE Hint on page 2-89 -- USE_NL Hint on page 2-96 USE_NL_WITH_INDEX Hint on page 2-97 NO_USE_NL Hint on page 2-89 Parallel Execution Hints PARALLEL Hint on page 2-90 NO_PARALLEL Hint on page 2-86 -- PARALLEL_INDEX Hint on page 2-91 NO_PARALLEL_INDEX Hint on page 2-87 -- PQ_DISTRIBUTE Hint on page 2-91 Query Transformation Hints FACT Hint on page 2-78 NO_FACT Hint on page 2-85 -- MERGE Hint on page 2-83 NO_MERGE Hint on page 2-86 -- NO_EXPAND Hint on page 2-84 USE_CONCAT Hint on page 2-95 -- REWRITE Hint on page 2-94 NO_REWRITE Hint on page 2-88 -- UNNEST Hint on page 2-95 NO_UNNEST Hint on page 2-88 -- STAR_TRANSFORMATION Hint on page 2-94 NO_STAR_TRANSFORMATION Hint on page 2-88 -- NO_QUERY_TRANSFORMATION Hint on page 2-88 Other Hints APPEND Hint on page 2-75 NOAPPEND Hint on page 2-84 Table 2–21 (Cont.) Hints by Functional Category Hint Link to Syntax and Semantics
- 109. Comments Basic Elements of Oracle SQL 2-75 Alphabetical Listing of Hints This section provides syntax and semantics for all hints in alphabetical order. ALL_ROWS Hint The ALL_ROWS hint instructs the optimizer to optimize a statement block with a goal of best throughput—that is, minimum total resource consumption. For example, the optimizer uses the query optimization approach to optimize this statement for best throughput: SELECT /*+ ALL_ROWS */ employee_id, last_name, salary, job_id FROM employees WHERE employee_id = 7566; If you specify either the ALL_ROWS or the FIRST_ROWS hint in a SQL statement, and if the data dictionary does not have statistics about tables accessed by the statement, then the optimizer uses default statistical values, such as allocated storage for such tables, to estimate the missing statistics and to subsequently choose an execution plan. These estimates might not be as accurate as those gathered by the DBMS_STATS package, so you should use the DBMS_STATS package to gather statistics. If you specify hints for access paths or join operations along with either the ALL_ROWS or FIRST_ROWS hint, then the optimizer gives precedence to the access paths and join operations specified by the hints. APPEND Hint -- CACHE Hint on page 2-76 NOCACHE Hint on page 2-84 -- CURSOR_SHARING_EXACT Hint on page 2-76 -- DRIVING_SITE Hint on page 2-77 -- DYNAMIC_SAMPLING Hint on page 2-77 -- PUSH_PRED Hint on page 2-92 NO_PUSH_PRED Hint on page 2-87 -- PUSH_SUBQ Hint on page 2-93 NO_PUSH_SUBQ Hint on page 2-87 -- PX_JOIN_FILTER Hint on page 2-93 NO_PX_JOIN_FILTER Hint on page 2-88 -- NO_XML_QUERY_REWRITE Hint on page 2-89 -- QB_NAME Hint on page 2-93 -- MODEL_MIN_ANALYSIS Hint on page 2-83 Table 2–21 (Cont.) Hints by Functional Category Hint Link to Syntax and Semantics /*+ ALL_ROWS */ /*+ APPEND */
- 110. Comments 2-76 Oracle Database SQL Reference The APPEND hint instructs the optimizer to use direct-path INSERT if your database is running in serial mode. Your database is in serial mode if you are not using Enterprise Edition. Conventional INSERT is the default in serial mode, and direct-path INSERT is the default in parallel mode. In direct-path INSERT, data is appended to the end of the table, rather than using existing space currently allocated to the table. As a result, direct-path INSERT can be considerably faster than conventional INSERT. CACHE Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The CACHE hint instructs the optimizer to place the blocks retrieved for the table at the most recently used end of the LRU list in the buffer cache when a full table scan is performed. This hint is useful for small lookup tables. In the following example, the CACHE hint overrides the default caching specification of the table: SELECT /*+ FULL (hr_emp) CACHE(hr_emp) */ last_name FROM employees hr_emp; The CACHE and NOCACHE hints affect system statistics table scans (long tables) and table scans (short tables), as shown in the V$SYSSTAT data dictionary view. CLUSTER Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The CLUSTER hint instructs the optimizer to use a cluster scan to access the specified table. This hint applies only to clustered tables. CURSOR_SHARING_EXACT Hint Oracle can replace literals in SQL statements with bind variables, when it is safe to do so. This replacement is controlled with the CURSOR_SHARING initialization parameter. The CURSOR_SHARING_EXACT hint instructs the optimizer to switch this behavior off. In other words, Oracle executes the SQL statement without any attempt to replace literals with bind variables. See Also: Oracle Database Administrator's Guide for information on direct-path inserts /*+ CACHE ( @ queryblock tablespec ) */ /*+ CLUSTER ( @ queryblock tablespec ) */ /*+ CURSOR_SHARING_EXACT */
- 111. Comments Basic Elements of Oracle SQL 2-77 DRIVING_SITE Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The DRIVING_SITE hint instructs the optimizer to execute the query at a different site than that selected by the database. This hint is useful if you are using distributed query optimization. For example: SELECT /*+ DRIVING_SITE(departments) */ * FROM employees, departments@rsite WHERE employees.department_id = departments.department_id; If this query is executed without the hint, then rows from departments are sent to the local site, and the join is executed there. With the hint, the rows from employees are sent to the remote site, and the query is executed there and the result set is returned to the local site. DYNAMIC_SAMPLING Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The DYNAMIC_SAMPLING hint instructs the optimizer how to control dynamic sampling to improve server performance by determining more accurate predicate selectivity and statistics for tables and indexes. You can set the value of DYNAMIC_SAMPLING to a value from 0 to 10. The higher the level, the more effort the compiler puts into dynamic sampling and the more broadly it is applied. Sampling defaults to cursor level unless you specify tablespec. The integer value is 0 to 10, indicating the degree of sampling. If a cardinality statistic already exists for the table, then the optimizer uses it. Otherwise, the optimizer enables dynamic sampling to estimate the cardinality statistic. If you specify tablespec and the cardinality statistic already exists, then: ■ If there is no single-table predicate (a WHERE clause that evaluates only one table), then the optimizer trusts the existing statistics and ignores this hint. For example, the following query will not result in any dynamic sampling if employees is analyzed: SELECT /*+ dynamic_sampling(e 1) */ count(*) FROM employees e; ■ If there is a single-table predicate, then the optimizer uses the existing cardinality statistic and estimates the selectivity of the predicate using the existing statistics. To apply dynamic sampling to a specific table, use the following form of the hint: SELECT /*+ dynamic_sampling(employees 1) */ * FROM employees WHERE .., /*+ DRIVING_SITE ( @ queryblock tablespec ) */ /*+ DYNAMIC_SAMPLING ( @ queryblock tablespec integer ) */
- 112. Comments 2-78 Oracle Database SQL Reference FACT Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The FACT hint is used in the context of the star transformation. It instructs the optimizer that the table specified in tablespec should be considered as a fact table. FIRST_ROWS Hint The FIRST_ROWS hint instructs Oracle to optimize an individual SQL statement for fast response, choosing the plan that returns the first n rows most efficiently. For integer, specify the number of rows to return. For example, the optimizer uses the query optimization approach to optimize the following statement for best response time: SELECT /*+ FIRST_ROWS(10) */ employee_id, last_name, salary, job_id FROM employees WHERE department_id = 20; In this example each department contains many employees. The user wants the first 10 employees of department 20 to be displayed as quickly as possible. The optimizer ignores this hint in DELETE and UPDATE statement blocks and in SELECT statement blocks that include any blocking operations, such as sorts or groupings. Such statements cannot be optimized for best response time, because Oracle Database must retrieve all rows accessed by the statement before returning the first row. If you specify this hint in any such statement, then the database optimizes for best throughput. FULL Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The FULL hint instructs the optimizer to perform a full table scan for the specified table. For example: See Also: Oracle Database Performance Tuning Guide for information about dynamic sampling and the sampling levels that you can set Note: The FIRST_ROWS hint specified without an argument, which optimizes for the best plan to return the first single row, is retained for backward compatibility and plan stability only. See Also: "ALL_ROWS Hint" on page 2-75 for additional information on the FIRST_ROWS hint and statistics /*+ FACT ( @ queryblock tablespec ) */ /*+ FIRST_ROWS ( integer ) */ /*+ FULL ( @ queryblock tablespec ) */
- 113. Comments Basic Elements of Oracle SQL 2-79 SELECT /*+ FULL(e) */ employee_id, last_name FROM hr.employees e WHERE last_name LIKE :b1; Oracle Database performs a full table scan on the employees table to execute this statement, even if there is an index on the last_name column that is made available by the condition in the WHERE clause. The employees table has alias e in the FROM clause, so the hint must refer to the table by its alias rather than by its name. Do not specify schema names in the hint even if they are specified in the FROM clause. HASH Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The HASH hint instructs the optimizer to use a hash scan to access the specified table. This hint applies only to tables stored in a table cluster. INDEX Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72, indexspec::= on page 2-73) The INDEX hint instructs the optimizer to use an index scan for the specified table. You can use the INDEX hint for function-based, domain, B-tree, bitmap, and bitmap join indexes. The behavior of the hint depends on the indexspec specification: ■ If the INDEX hint specifies a single available index, then the database performs a scan on this index. The optimizer does not consider a full table scan or a scan of another index on the table. ■ For a hint on a combination of multiple indexes, Oracle recommends using INDEX_COMBINE rather than INDEX, because it is a more versatile hint. If the INDEX hint specifies a list of available indexes, then the optimizer considers the cost of a scan on each index in the list and then performs the index scan with the lowest cost. The database can also choose to scan multiple indexes from this list and merge the results, if such an access path has the lowest cost. The database does not consider a full table scan or a scan on an index not listed in the hint. ■ If the INDEX hint specifies no indexes, then the optimizer considers the cost of a scan on each available index on the table and then performs the index scan with the lowest cost. The database can also choose to scan multiple indexes and merge the results, if such an access path has the lowest cost. The optimizer does not consider a full table scan. For example: SELECT /*+ INDEX (employees emp_department_ix)*/ employee_id, department_id FROM employees /*+ HASH ( @ queryblock tablespec ) */ /*+ INDEX ( @ queryblock tablespec indexspec ) */
- 114. Comments 2-80 Oracle Database SQL Reference WHERE department_id > 50; INDEX_ASC Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72, indexspec::= on page 2-73) The INDEX_ASC hint instructs the optimizer to use an index scan for the specified table. If the statement uses an index range scan, then Oracle Database scans the index entries in ascending order of their indexed values. Each parameter serves the same purpose as in "INDEX Hint" on page 2-79. The default behavior for a range scan is to scan index entries in ascending order of their indexed values, or in descending order for a descending index. This hint does not change the default order of the index, and therefore does not specify anything more than the INDEX hint. However, you can use the INDEX_ASC hint to specify ascending range scans explicitly should the default behavior change. INDEX_COMBINE Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72, indexspec::= on page 2-73) The INDEX_COMBINE hint instructs the optimizer to use a bitmap access path for the table. If indexspec is omitted from the INDEX_COMBINE hint, then the optimizer uses whatever Boolean combination of indexes has the best cost estimate for the table. If you specify indexspec, then the optimizer tries to use some Boolean combination of the specified indexes. Each parameter serves the same purpose as in "INDEX Hint" on page 2-79. For example: SELECT /*+ INDEX_COMBINE(e emp_manager_ix emp_department_ix) */ * FROM employees e WHERE manager_id = 108 OR department_id = 110; INDEX_DESC Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72, indexspec::= on page 2-73) The INDEX_DESC hint instructs the optimizer to use a descending index scan for the specified table. If the statement uses an index range scan and the index is ascending, then Oracle scans the index entries in descending order of their indexed values. In a partitioned index, the results are in descending order within each partition. For a descending index, this hint effectively cancels out the descending order, resulting in a /*+ INDEX_ASC ( @ queryblock tablespec indexspec ) */ /*+ INDEX_COMBINE ( @ queryblock tablespec indexspec ) */ /*+ INDEX_DESC ( @ queryblock tablespec indexspec ) */
- 115. Comments Basic Elements of Oracle SQL 2-81 scan of the index entries in ascending order. Each parameter serves the same purpose as in "INDEX Hint" on page 2-79. For example: SELECT /*+ INDEX_DESC(e emp_name_ix) */ * FROM employees e; INDEX_FFS Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72, indexspec::= on page 2-73) The INDEX_FFS hint instructs the optimizer to perform a fast full index scan rather than a full table scan. Each parameter serves the same purpose as in "INDEX Hint" on page 2-79. For example: SELECT /*+ INDEX_FFS(e emp_name_ix) */ first_name FROM employees e; INDEX_JOIN Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72, indexspec::= on page 2-73) The INDEX_JOIN hint instructs the optimizer to use an index join as an access path. For the hint to have a positive effect, a sufficiently small number of indexes must exist that contain all the columns required to resolve the query. Each parameter serves the same purpose as in "INDEX Hint" on page 2-79. For example, the following query uses an index join to access the manager_id and department_id columns, both of which are indexed in the employees table. SELECT /*+ INDEX_JOIN(e emp_manager_ix emp_department_ix) */ department_id FROM employees e WHERE manager_id < 110 AND department_id < 50; INDEX_SS Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72, indexspec::= on page 2-73) The INDEX_SS hint instructs the optimizer to perform an index skip scan for the specified table. If the statement uses an index range scan, then Oracle scans the index See Also: Oracle Database Performance Tuning Guide for information on full scans /*+ INDEX_FFS ( @ queryblock tablespec indexspec ) */ /*+ INDEX_JOIN ( @ queryblock tablespec indexspec ) */ /*+ INDEX_SS ( @ queryblock tablespec indexspec ) */
- 116. Comments 2-82 Oracle Database SQL Reference entries in ascending order of their indexed values. In a partitioned index, the results are in ascending order within each partition. Each parameter serves the same purpose as in "INDEX Hint" on page 2-79. For example: SELECT /*+ INDEX_SS(e emp_name_ix) */ last_name FROM employees e WHERE first_name = 'Steven'; INDEX_SS_ASC Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72, indexspec::= on page 2-73) The INDEX_SS_ASC hint instructs the optimizer to perform an index skip scan for the specified table. If the statement uses an index range scan, then Oracle Database scans the index entries in ascending order of their indexed values. In a partitioned index, the results are in ascending order within each partition. Each parameter serves the same purpose as in "INDEX Hint" on page 2-79. The default behavior for a range scan is to scan index entries in ascending order of their indexed values, or in descending order for a descending index. This hint does not change the default order of the index, and therefore does not specify anything more than the INDEX_SS hint. However, you can use the INDEX_SS_ASC hint to specify ascending range scans explicitly should the default behavior change. INDEX_SS_DESC Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72, indexspec::= on page 2-73) The INDEX_SS_DESC hint instructs the optimizer to perform an index skip scan for the specified table. If the statement uses an index range scan and the index is ascending, then Oracle scans the index entries in descending order of their indexed values. In a partitioned index, the results are in descending order within each partition. For a descending index, this hint effectively cancels out the descending order, resulting in a scan of the index entries in ascending order. Each parameter serves the same purpose as in the "INDEX Hint" on page 2-79. For example: SELECT /*+ INDEX_SS_DESC(e emp_name_ix) */ last_name FROM employees e WHERE first_name = ’Steven’; See Also: Oracle Database Performance Tuning Guide for information on index skip scans See Also: Oracle Database Performance Tuning Guide for information on index skip scans /*+ INDEX_SS_ASC ( @ queryblock tablespec indexspec ) */ /*+ INDEX_SS_DESC ( @ queryblock tablespec indexspec ) */
- 117. Comments Basic Elements of Oracle SQL 2-83 LEADING Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The LEADING hint instructs the optimizer to use the specified set of tables as the prefix in the execution plan. This hint is more versatile than the ORDERED hint. For example: SELECT /*+ LEADING(e j) */ * FROM employees e, departments d, job_history j WHERE e.department_id = d.department_id AND e.hire_date = j.start_date; The LEADING hint is ignored if the tables specified cannot be joined first in the order specified because of dependencies in the join graph. If you specify two or more conflicting LEADING hints, then all of them are ignored. If you specify the ORDERED hint, it overrides all LEADING hints. MERGE Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The MERGE hint lets you merge views in a query. If a view's query block contains a GROUP BY clause or DISTINCT operator in the SELECT list, then the optimizer can merge the view into the accessing statement only if complex view merging is enabled. Complex merging can also be used to merge an IN subquery into the accessing statement if the subquery is uncorrelated. For example: SELECT /*+ MERGE(v) */ e1.last_name, e1.salary, v.avg_salary FROM employees e1, (SELECT department_id, avg(salary) avg_salary FROM employees e2 GROUP BY department_id) v WHERE e1.department_id = v.department_id AND e1.salary > v.avg_salary; When the MERGE hint is used without an argument, it should be placed in the view query block. When MERGE is used with the view name as an argument, it should be placed in the surrounding query. MODEL_MIN_ANALYSIS Hint See Also: Oracle Database Performance Tuning Guide for information on index skip scans /*+ LEADING ( @ queryblock tablespec ) */ /*+ MERGE ( @ queryblock @ queryblock tablespec ) */ /*+ MODEL_MIN_ANALYSIS */
- 118. Comments 2-84 Oracle Database SQL Reference The MODEL_MIN_ANALYSIS hint instructs the optimizer to omit some compile-time optimizations of spreadsheet rules—primarily detailed dependency graph analysis. Other spreadsheet optimizations, such as creating filters to selectively populate spreadsheet access structures and limited rule pruning, are still used by the optimizer. This hint reduces compilation time because spreadsheet analysis can be lengthy if the number of spreadsheet rules is more than several hundreds. NOAPPEND Hint The NOAPPEND hint instructs the optimizer to use conventional INSERT by disabling parallel mode for the duration of the INSERT statement. Conventional INSERT is the default in serial mode, and direct-path INSERT is the default in parallel mode. NOCACHE Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The NOCACHE hint instructs the optimizer to place the blocks retrieved for the table at the least recently used end of the LRU list in the buffer cache when a full table scan is performed. This is the normal behavior of blocks in the buffer cache. For example: SELECT /*+ FULL(hr_emp) NOCACHE(hr_emp) */ last_name FROM employees hr_emp; The CACHE and NOCACHE hints affect system statistics table scans(long tables) and table scans(short tables), as shown in the V$SYSSTAT view. NO_EXPAND Hint (See "Specifying a Query Block in a Hint" on page 2-73) The NO_EXPAND hint instructs the optimizer not to consider OR-expansion for queries having OR conditions or IN-lists in the WHERE clause. Usually, the optimizer considers using OR expansion and uses this method if it decides that the cost is lower than not using it. For example: SELECT /*+ NO_EXPAND */ * FROM employees e, departments d WHERE e.manager_id = 108 OR d.department_id = 110; See Also: Oracle Database Performance Tuning Guide for information on automatic caching of tables, depending on their size /*+ NOAPPEND */ /*+ NOCACHE ( @ queryblock tablespec ) */ /*+ NO_EXPAND ( @ queryblock ) */
- 119. Comments Basic Elements of Oracle SQL 2-85 NO_FACT Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The NO_FACT hint is used in the context of the star transformation. It instruct the optimizer that the queried table should not be considered as a fact table. NO_INDEX Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72, indexspec::= on page 2-73) The NO_INDEX hint instructs the optimizer not to use one or more indexes for the specified table. For example: SELECT /*+ NO_INDEX(employees emp_empid) */ employee_id FROM employees WHERE employee_id > 200; Each parameter serves the same purpose as in "INDEX Hint" on page 2-79 with the following modifications: ■ If this hint specifies a single available index, then the optimizer does not consider a scan on this index. Other indexes not specified are still considered. ■ If this hint specifies a list of available indexes, then the optimizer does not consider a scan on any of the specified indexes. Other indexes not specified in the list are still considered. ■ If this hint specifies no indexes, then the optimizer does not consider a scan on any index on the table. This behavior is the same as a NO_INDEX hint that specifies a list of all available indexes for the table. The NO_INDEX hint applies to function-based, B-tree, bitmap, cluster, or domain indexes. If a NO_INDEX hint and an index hint (INDEX, INDEX_ASC, INDEX_DESC, INDEX_COMBINE, or INDEX_FFS) both specify the same indexes, then the database ignores both the NO_INDEX hint and the index hint for the specified indexes and considers those indexes for use during execution of the statement. NO_INDEX_FFS Hint See Also: ■ Oracle Database Performance Tuning Guide for a discussion of OR-expansion ■ the "USE_CONCAT Hint" on page 2-95, which is the opposite of this hint /*+ NO_FACT ( @ queryblock tablespec ) */ /*+ NO_INDEX ( @ queryblock tablespec indexspec ) */ /*+ NO_INDEX_FFS ( @ queryblock tablespec indexspec ) */
- 120. Comments 2-86 Oracle Database SQL Reference (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72, indexspec::= on page 2-73) The NO_INDEX_FFS hint instructs the optimizer to exclude a fast full index scan of the specified indexes on the specified table. Each parameter serves the same purpose as in the "INDEX Hint" on page 2-79. For example: SELECT /*+ NO_INDEX_FFS(items item_order_ix) */ order_id FROM order_items items; NO_INDEX_SS Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72, indexspec::= on page 2-73) The NO_INDEX_SS hint instructs the optimizer to exclude a skip scan of the specified indexes on the specified table. Each parameter serves the same purpose as in the "INDEX Hint" on page 2-79. NO_MERGE Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The NO_MERGE hint instructs the optimizer not to combine the outer query and any inline view queries into a single query. This hint lets you have more influence over the way in which the view is accessed. For example, the following statement causes view seattle_dept not to be merged.: SELECT /*+NO_MERGE(seattle_dept)*/ e1.last_name, seattle_dept.department_name FROM employees e1, (SELECT location_id, department_id, department_name FROM departments WHERE location_id = 1700) seattle_dept WHERE e1.department_id = seattle_dept.department_id; When you use the NO_MERGE hint in the view query block, specify it without an argument. When you specify NO_MERGE in the surrounding query, specify it with the view name as an argument. NO_PARALLEL Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) See Also: Oracle Database Performance Tuning Guide for information on index skip scans /*+ NO_INDEX_SS ( @ queryblock tablespec indexspec ) */ /*+ NO_MERGE ( @ queryblock @ queryblock tablespec ) */ /*+ NO_PARALLEL ( @ queryblock tablespec ) */
- 121. Comments Basic Elements of Oracle SQL 2-87 The NO_PARALLEL hint overrides a PARALLEL parameter in the DDL that created or altered the table. For example: SELECT /*+ NO_PARALLEL(hr_emp) */ last_name FROM employees hr_emp; NOPARALLEL Hint The NOPARALLEL hint has been deprecated. Use the NO_PARALLEL hint instead. NO_PARALLEL_INDEX Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72, indexspec::= on page 2-73) The NO_PARALLEL_INDEX hint overrides a PARALLEL parameter in the DDL that created or altered the index, thus avoiding a parallel index scan operation. NOPARALLEL_INDEX Hint The NOPARALLEL_INDEX hint has been deprecated. Use the NO_PARALLEL_INDEX hint instead. NO_PUSH_PRED Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The NO_PUSH_PRED hint instructs the optimizer not to push a join predicate into the view. For example: SELECT /*+ NO_MERGE(v) NO_PUSH_PRED(v) */ * FROM employees e, (SELECT manager_id FROM employees ) v WHERE e.manager_id = v.manager_id(+) AND e.employee_id = 100; NO_PUSH_SUBQ Hint (See "Specifying a Query Block in a Hint" on page 2-73) The NO_PUSH_SUBQ hint instructs the optimizer to evaluate nonmerged subqueries as the last step in the execution plan. Doing so can improve performance if the subquery is relatively expensive or does not reduce the number of rows significantly. /*+ NO_PARALLEL_INDEX ( @ queryblock tablespec indexspec ) */ /*+ NO_PUSH_PRED ( @ queryblock @ queryblock tablespec ) */ /*+ NO_PUSH_SUBQ ( @ queryblock ) */
- 122. Comments 2-88 Oracle Database SQL Reference NO_PX_JOIN_FILTER Hint This hint prevents the optimizer from using parallel join bitmap filtering. NO_REWRITE Hint (See "Specifying a Query Block in a Hint" on page 2-73) The NO_REWRITE hint instructs the optimizer to disable query rewrite for the query block, overriding the setting of the parameter QUERY_REWRITE_ENABLED. For example: SELECT /*+ NO_REWRITE */ sum(s.amount_sold) AS dollars FROM sales s, times t WHERE s.time_id = t.time_id GROUP BY t.calendar_month_desc; NOREWRITE Hint The NOREWRITE hint has been deprecated. Use the NO_REWRITE hint instead. NO_QUERY_TRANSFORMATION Hint The NO_QUERY_TRANSFORMATION hint instructs the optimizer to skip all query transformations, including but not limited to OR-expansion, view merging, subquery unnesting, star transformation, and materialized view rewrite. For example: SELECT /*+ NO_QUERY_TRANSFORMATION */ employee_id, last_name FROM (SELECT * FROM employees e) v WHERE v.last_name = ’Smith’; NO_STAR_TRANSFORMATION Hint (See "Specifying a Query Block in a Hint" on page 2-73) The NO_STAR_TRANSFORMATION hint instructs the optimizer not to perform star query transformation. NO_UNNEST Hint (See "Specifying a Query Block in a Hint" on page 2-73) Use of the NO_UNNEST hint turns off unnesting . /*+ NO_PX_JOIN_FILTER ( tablespec ) */ /*+ NO_REWRITE ( @ queryblock ) */ /*+ NO_QUERY_TRANSFORMATION */ /*+ NO_STAR_TRANSFORMATION ( @ queryblock ) */ /*+ NO_UNNEST ( @ queryblock ) */
- 123. Comments Basic Elements of Oracle SQL 2-89 NO_USE_HASH Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The NO_USE_HASH hint instructs the optimizer to exclude hash joins when joining each specified table to another row source using the specified table as the inner table. For example: SELECT /*+ NO_USE_HASH(e d) */ * FROM employees e, departments d WHERE e.department_id = d.department_id; NO_USE_MERGE Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The NO_USE_MERGE hint instructs the optimizer to exclude sort-merge joins when joining each specified table to another row source using the specified table as the inner table. For example: SELECT /*+ NO_USE_MERGE(e d) */ * FROM employees e, departments d WHERE e.department_id = d.department_id ORDER BY d.department_id; NO_USE_NL Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The NO_USE_NL hint instructs the optimizer to exclude nested loops joins when joining each specified table to another row source using the specified table as the inner table. For example: SELECT /*+ NO_USE_NL(l h) */ * FROM orders h, order_items l WHERE l.order_id = h.order_id AND l.order_id > 3500; When this hint is specified, only hash join and sort-merge joins are considered for the specified tables. However, in some cases tables can be joined only by using nested loops. In such cases, the optimizer ignores the hint for those tables. NO_XML_QUERY_REWRITE Hint The NO_XML_QUERY_REWRITE hint instructs the optimizer to prohibit the rewriting of XPath expressions in SQL statements. For example: /*+ NO_USE_HASH ( @ queryblock tablespec ) */ /*+ NO_USE_MERGE ( @ queryblock tablespec ) */ /*+ NO_USE_NL ( @ queryblock tablespec ) */ /*+ NO_XML_QUERY_REWRITE */
- 124. Comments 2-90 Oracle Database SQL Reference SELECT /*+NO_XML_QUERY_REWRITE*/ XMLQUERY(’<A/>’) FROM dual; ORDERED Hint The ORDERED hint instructs Oracle to join tables in the order in which they appear in the FROM clause. Oracle recommends that you use the LEADING hint, which is more versatile than the ORDERED hint. When you omit the ORDERED hint from a SQL statement requiring a join, the optimizer chooses the order in which to join the tables. You might want to use the ORDERED hint to specify a join order if you know something that the optimizer does not know about the number of rows selected from each table. Such information lets you choose an inner and outer table better than the optimizer could. The following query is an example of the use of the ORDERED hint: SELECT /*+ORDERED */ o.order_id, c.customer_id, l.unit_price * l.quantity FROM customers c, order_items l, orders o WHERE c.cust_last_name = :b1 AND o.customer_id = c.customer_id AND o.order_id = l.order_id; PARALLEL Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The PARALLEL hint instructs the optimizer to use the specified number of concurrent servers for a parallel operation. The hint applies to the SELECT, INSERT, MERGE, UPDATE, and DELETE portions of a statement, as well as to the table scan portion. If any parallel restrictions are violated, then the hint is ignored. The integer value specifies the degree of parallelism for the specified table. Specifying DEFAULT or no value signifies that the query coordinator should examine the settings of the initialization parameters to determine the default degree of parallelism. In the following example, the PARALLEL hint overrides the degree of parallelism specified in the employees table definition: SELECT /*+ FULL(hr_emp) PARALLEL(hr_emp, 5) */ last_name FROM employees hr_emp; In the next example, the PARALLEL hint overrides the degree of parallelism specified in the employees table definition and instructs the optimizer to use the default degree of parallelism determined by the initialization parameters. SELECT /*+ FULL(hr_emp) PARALLEL(hr_emp, DEFAULT) */ last_name Note: The number of servers that can be used is twice the value in the PARALLEL hint, if sorting or grouping operations also take place. /*+ ORDERED */ /*+ PARALLEL ( @ queryblock tablespec integer DEFAULT ) */
- 125. Comments Basic Elements of Oracle SQL 2-91 FROM employees hr_emp; Oracle ignores parallel hints on temporary tables. Please refer to CREATE TABLE on page 16-6 and Oracle Database Concepts for more information on parallel execution. PARALLEL_INDEX Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72, indexspec::= on page 2-73) The PARALLEL_INDEX hint instructs the optimizer to use the specified number of concurrent servers to parallelize index range scans for partitioned indexes. The integer value indicates the degree of parallelism for the specified index. Specifying DEFAULT or no value signifies that the query coordinator should examine the settings of the initialization parameters to determine the default degree of parallelism. For example, the following hint indicates three parallel execution processes are to be used: SELECT /*+ PARALLEL_INDEX(table1, index1, 3) */ PQ_DISTRIBUTE Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The PQ_DISTRIBUTE hint instructs the optimizer how to distribute rows of joined tables among producer and consumer query servers. Such distribution can improve the performance of parallel join operations. ■ outer_distribution is the distribution for the outer table. ■ inner_distribution is the distribution for the inner table. The values of the distributions are HASH, BROADCAST, PARTITION, and NONE. Only six combinations table distributions are valid, as described in Table 2–22: Table 2–22 Distribution Hint Combinations Distribution Description HASH, HASH The rows of each table are mapped to consumer query servers, using a hash function on the join keys. When mapping is complete, each query server performs the join between a pair of resulting partitions. This distribution is recommended when the tables are comparable in size and the join operation is implemented by hash-join or sort merge join. /*+ PARALLEL_INDEX ( @ queryblock tablespec indexspec integer DEFAULT ) */ /*+ PQ_DISTRIBUTE ( @ queryblock tablespec outer_distribution inner_distribution ) */
- 126. Comments 2-92 Oracle Database SQL Reference For example, given two tables r and s that are joined using a hash join, the following query contains a hint to use hash distribution: SELECT /*+ORDERED PQ_DISTRIBUTE(s HASH, HASH) USE_HASH (s)*/ column_list FROM r,s WHERE r.c=s.c; To broadcast the outer table r, the query is: SELECT /*+ORDERED PQ_DISTRIBUTE(s BROADCAST, NONE) USE_HASH (s) */ column_list FROM r,s WHERE r.c=s.c; PUSH_PRED Hint BROADCAST, NONE All rows of the outer table are broadcast to each query server. The inner table rows are randomly partitioned. This distribution is recommended when the outer table is very small compared with the inner table. As a general rule, use this distribution when the inner table size multiplied by the number of query servers is greater than the outer table size. NONE, BROADCAST All rows of the inner table are broadcast to each consumer query server. The outer table rows are randomly partitioned. This distribution is recommended when the inner table is very small compared with the outer table. As a general rule, use this distribution when the inner table size multiplied by the number of query servers is less than the outer table size. PARTITION, NONE The rows of the outer table are mapped using the partitioning of the inner table. The inner table must be partitioned on the join keys. This distribution is recommended when the number of partitions of the outer table is equal to or nearly equal to a multiple of the number of query servers; for example, 14 partitions and 15 query servers. Note: The optimizer ignores this hint if the inner table is not partitioned or not equijoined on the partitioning key. NONE, PARTITION The rows of the inner table are mapped using the partitioning of the outer table. The outer table must be partitioned on the join keys. This distribution is recommended when the number of partitions of the outer table is equal to or nearly equal to a multiple of the number of query servers; for example, 14 partitions and 15 query servers. Note: The optimizer ignores this hint if the outer table is not partitioned or not equijoined on the partitioning key. NONE, NONE Each query server performs the join operation between a pair of matching partitions, one from each table. Both tables must be equipartitioned on the join keys. See Also: Oracle Database Concepts for more information on how Oracle parallelizes join operations Table 2–22 (Cont.) Distribution Hint Combinations Distribution Description /*+ PUSH_PRED ( @ queryblock @ queryblock tablespec ) */
- 127. Comments Basic Elements of Oracle SQL 2-93 (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The PUSH_PRED hint instructs the optimizer to push a join predicate into the view. For example: SELECT /*+ NO_MERGE(v) PUSH_PRED(v) */ * FROM employees e, (SELECT manager_id FROM employees ) v WHERE e.manager_id = v.manager_id(+) AND e.employee_id = 100; PUSH_SUBQ Hint (See "Specifying a Query Block in a Hint" on page 2-73) The PUSH_SUBQ hint instructs the optimizer to evaluate nonmerged subqueries at the earliest possible step in the execution plan. Generally, subqueries that are not merged are executed as the last step in the execution plan. If the subquery is relatively inexpensive and reduces the number of rows significantly, then evaluating the subquery earlier can improve performance. This hint has no effect if the subquery is applied to a remote table or one that is joined using a merge join. PX_JOIN_FILTER Hint This hint forces the optimizer to use parallel join bitmap filtering. QB_NAME Hint (See "Specifying a Query Block in a Hint" on page 2-73) Use the QB_NAME hint to define a name for a query block. This name can then be used in a hint in the outer query or even in a hint in an inline view to affect query execution on the tables appearing in the named query block. If two or more query blocks have the same name, or if the same query block is hinted twice with different names, then the optimizer ignores all the names and the hints referencing that query block. Query blocks that are not named using this hint have unique system-generated names. These names can be displayed in the plan table and can also be used in hints within the query block, or in query block hints. For example: SELECT /*+ QB_NAME(qb) FULL(@qb e) */ employee_id, last_name FROM employees e WHERE last_name = ’Smith’; /*+ PUSH_SUBQ ( @ queryblock ) */ /*+ PX_JOIN_FILTER ( tablespec ) */ /*+ QB_NAME ( queryblock ) */
- 128. Comments 2-94 Oracle Database SQL Reference REWRITE Hint (See "Specifying a Query Block in a Hint" on page 2-73) The REWRITE hint instructs the optimizer to rewrite a query in terms of materialized views, when possible, without cost consideration. Use the REWRITE hint with or without a view list. If you use REWRITE with a view list and the list contains an eligible materialized view, then Oracle uses that view regardless of its cost. Oracle does not consider views outside of the list. If you do not specify a view list, then Oracle searches for an eligible materialized view and always uses it regardless of the cost of the final plan. RULE Hint The RULE hint disables the use of the optimizer. This hint is not supported and should not be used. STAR_TRANSFORMATION Hint (See "Specifying a Query Block in a Hint" on page 2-73) The STAR_TRANSFORMATION hint instructs the optimizer to use the best plan in which the transformation has been used. Without the hint, the optimizer could make a query optimization decision to use the best plan generated without the transformation, instead of the best plan for the transformed query. For example: SELECT /*+ STAR_TRANSFORMATION */ * FROM sales s, times t, products p, channels c WHERE s.time_id = t.time_id AND s.prod_id = p.product_id AND s.channel_id = c.channel_id AND p.product_status = 'obsolete'; Even if the hint is specified, there is no guarantee that the transformation will take place. The optimizer generates the subqueries only if it seems reasonable to do so. If no subqueries are generated, then there is no transformed query, and the best plan for the untransformed query is used, regardless of the hint. See Also: ■ Oracle Database Concepts and Oracle Database Advanced Replication for more information on materialized views ■ Oracle Database Data Warehousing Guide for more information on using REWRITE with materialized views /*+ REWRITE ( @ queryblock view ) */ /*+ RULE */ /*+ STAR_TRANSFORMATION ( @ queryblock ) */
- 129. Comments Basic Elements of Oracle SQL 2-95 UNNEST Hint (See "Specifying a Query Block in a Hint" on page 2-73) The UNNEST hint instructs the optimizer to unnest and merge the body of the subquery into the body of the query block that contains it, allowing the optimizer to consider them together when evaluating access paths and joins. Before a subquery is unnested, the optimizer first verifies whether the statement is valid. The statement must then must pass heuristic and query optimization tests. The UNNEST hint instructs the optimizer to check the subquery block for validity only. If the subquery block is valid, then subquery unnesting is enabled without checking the heuristics or costs. USE_CONCAT Hint (See "Specifying a Query Block in a Hint" on page 2-73) The USE_CONCAT hint instructs the optimizer to transform combined OR-conditions in the WHERE clause of a query into a compound query using the UNION ALL set operator. Without this hint, this transformation occurs only if the cost of the query using the concatenations is cheaper than the cost without them. The USE_CONCAT hint overrides the cost consideration. For example: SELECT /*+ USE_CONCAT */ * FROM employees e WHERE manager_id = 108 OR department_id = 110; See Also: ■ Oracle Database Data Warehousing Guide for a full discussion of star transformation. ■ Oracle Database Reference for more information on the STAR_ TRANSFORMATION_ENABLED initialization parameter. See Also: ■ "Collection Unnesting: Examples" on page 19-44 for more information on unnesting nested subqueries and the conditions that make a subquery block valid ■ Oracle Database Performance Tuning Guide for additional information on subquery unnesting See Also: the "NO_EXPAND Hint" on page 2-84, which is the opposite of this hint and Oracle Database Performance Tuning Guide for a discussion of OR-expansion /*+ UNNEST ( @ queryblock ) */ /*+ USE_CONCAT ( @ queryblock ) */
- 130. Comments 2-96 Oracle Database SQL Reference USE_HASH Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The USE_HASH hint instructs the optimizer to join each specified table with another row source using a hash join. For example: SELECT /*+ USE_HASH(l h) */ * FROM orders h, order_items l WHERE l.order_id = h.order_id AND l.order_id > 3500; USE_MERGE Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The USE_MERGE hint instructs the optimizer to join each specified table with another row source using a sort-merge join. For example: SELECT /*+ USE_MERGE(employees departments) */ * FROM employees, departments WHERE employees.department_id = departments.department_id; Use of the USE_NL and USE_MERGE hints is recommended with the LEADING and ORDERED hints. The optimizer uses those hints when the referenced table is forced to be the inner table of a join. The hints are ignored if the referenced table is the outer table. USE_NL Hint The USE_NL hint instructs the optimizer to join each specified table to another row source with a nested loops join, using the specified table as the inner table. (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72) The USE_NL hint instructs the optimizer to join each specified table to another row source with a nested loops join, using the specified table as the inner table. Use of the USE_NL and USE_MERGE hints is recommended with the LEADING and ORDERED hints. The optimizer uses those hints when the referenced table is forced to be the inner table of a join. The hints are ignored if the referenced table is the outer table. In the following example, where a nested loop is forced through a hint, orders is accessed through a full table scan and the filter condition l.order_id = h.order_ id is applied to every row. For every row that meets the filter condition, order_ items is accessed through the index order_id. SELECT /*+ USE_NL(l h) */ h.customer_id, l.unit_price * l.quantity FROM orders h ,order_items l WHERE l.order_id = h.order_id; /*+ USE_HASH ( @ queryblock tablespec ) */ /*+ USE_MERGE ( @ queryblock tablespec ) */ /*+ USE_NL ( @ queryblock tablespec ) */
- 131. Database Objects Basic Elements of Oracle SQL 2-97 Adding an INDEX hint to the query could avoid the full table scan on orders, resulting in an execution plan similar to one used on larger systems, even though it might not be particularly efficient here. USE_NL_WITH_INDEX Hint (See "Specifying a Query Block in a Hint" on page 2-73, tablespec::= on page 2-72, indexspec::= on page 2-73) The USE_NL_WITH_INDEX hint instructs the optimizer to join the specified table to another row source with a nested loops join using the specified table as the inner table. For example: SELECT /*+ USE_NL_WITH_INDEX(l item_product_ix) */ * FROM orders h, order_items l WHERE l.order_id = h.order_id AND l.order_id > 3500; The following conditions apply: ■ If no index is specified, then the optimizer must be able to use some index with at least one join predicate as the index key. ■ If an index is specified, then the optimizer must be able to use that index with at least one join predicate as the index key. Database Objects Oracle Database recognizes objects that are associated with a particular schema and objects that are not associated with a particular schema, as described in the sections that follow. Schema Objects A schema is a collection of logical structures of data, or schema objects. A schema is owned by a database user and has the same name as that user. Each user owns a single schema. Schema objects can be created and manipulated with SQL and include the following types of objects: Clusters Constraints Database links Database triggers Dimensions External procedure libraries Index-organized tables Indexes Indextypes Java classes, Java resources, Java sources Materialized views Materialized view logs Object tables Object types /*+ USE_NL_WITH_INDEX ( @ queryblock tablespec indexspec ) */
- 132. Schema Object Names and Qualifiers 2-98 Oracle Database SQL Reference Object views Operators Packages Sequences Stored functions, stored procedures Synonyms Tables Views Nonschema Objects Other types of objects are also stored in the database and can be created and manipulated with SQL but are not contained in a schema: Contexts Directories Parameter files (PFILEs) and server parameter files (SPFILEs) Profiles Roles Rollback segments Tablespaces Users In this reference, each type of object is briefly defined in Chapter 10 through Chapter 19, in the section describing the statement that creates the database object. These statements begin with the keyword CREATE. For example, for the definition of a cluster, see CREATE CLUSTER on page 14-2. You must provide names for most types of database objects when you create them. These names must follow the rules listed in the following sections. Schema Object Names and Qualifiers Some schema objects are made up of parts that you can or must name, such as the columns in a table or view, index and table partitions and subpartitions, integrity constraints on a table, and objects that are stored within a package, including procedures and stored functions. This section provides: ■ Rules for naming schema objects and schema object location qualifiers ■ Guidelines for naming schema objects and qualifiers Schema Object Naming Rules Every database object has a name. In a SQL statement, you represent the name of an object with a quoted identifier or a nonquoted identifier. ■ A quoted identifier begins and ends with double quotation marks ("). If you name a schema object using a quoted identifier, then you must use the double quotation marks whenever you refer to that object. ■ A nonquoted identifier is not surrounded by any punctuation. See Also: Oracle Database Concepts for an overview of database objects
- 133. Schema Object Names and Qualifiers Basic Elements of Oracle SQL 2-99 You can use either quoted or nonquoted identifiers to name any database object. However, database names, global database names, and database link names are always case insensitive and are stored as uppercase. If you specify such names as quoted identifiers, then the quotation marks are silently ignored. Please refer to CREATE USER on page 17-26 for additional rules for naming users and passwords. The following list of rules applies to both quoted and nonquoted identifiers unless otherwise indicated: 1. Names must be from 1 to 30 bytes long with these exceptions: ■ Names of databases are limited to 8 bytes. ■ Names of database links can be as long as 128 bytes. If an identifier includes multiple parts separated by periods, then each attribute can be up to 30 bytes long. Each period separator, as well as any surrounding double quotation marks, counts as one byte. For example, suppose you identify a column like this: "schema"."table"."column" The schema name can be 30 bytes, the table name can by 30 bytes, and the column name can be 30 bytes. Each of the quotation marks and periods is a single-byte character, so the total length of the identifier in this example can be up to 98 bytes. 2. Nonquoted identifiers cannot be Oracle Database reserved words. Quoted identifiers can be reserved words, although this is not recommended. Depending on the Oracle product you plan to use to access a database object, names might be further restricted by other product-specific reserved words. 3. The Oracle SQL language contains other words that have special meanings. These words include datatypes, schema names, function names, the dummy system table DUAL, and keywords (the uppercase words in SQL statements, such as DIMENSION, SEGMENT, ALLOCATE, DISABLE, and so forth). These words are not reserved. However, Oracle uses them internally in specific ways. Therefore, if you use these words as names for objects and object parts, then your SQL statements may be more difficult to read and may lead to unpredictable results. In particular, do not use words beginning with SYS_ as schema object names, and do not use the names of SQL built-in functions for the names of schema objects or user-defined functions. Note: The reserved word ROWID is an exception to this rule. You cannot use the uppercase word ROWID, either quoted or nonquoted, as a column name. However, you can use the uppercase word as a quoted identifier that is not a column name, and you can use the word with one or more lowercase letters (for example, "Rowid" or "rowid") as any quoted identifier, including a column name. See Also: ■ Appendix D, "Oracle Database Reserved Words" for a listing of all Oracle Database reserved words ■ The manual for a specific product, such as Oracle Database PL/SQL User's Guide and Reference, for a list of the reserved words of that product
- 134. Schema Object Names and Qualifiers 2-100 Oracle Database SQL Reference 4. You should use ASCII characters in database names, global database names, and database link names, because ASCII characters provide optimal compatibility across different platforms and operating systems. 5. Nonquoted identifiers must begin with an alphabetic character from your database character set. Quoted identifiers can begin with any character. 6. Nonquoted identifiers can contain only alphanumeric characters from your database character set and the underscore (_), dollar sign ($), and pound sign (#). Database links can also contain periods (.) and "at" signs (@). Oracle strongly discourages you from using $ and # in nonquoted identifiers. Quoted identifiers can contain any characters and punctuations marks as well as spaces. However, neither quoted nor nonquoted identifiers can contain double quotation marks or the null character (0). 7. Within a namespace, no two objects can have the same name. The following schema objects share one namespace: ■ Tables ■ Views ■ Sequences ■ Private synonyms ■ Stand-alone procedures ■ Stand-alone stored functions ■ Packages ■ Materialized views ■ User-defined types Each of the following schema objects has its own namespace: ■ Indexes ■ Constraints ■ Clusters ■ Database triggers ■ Private database links ■ Dimensions Because tables and views are in the same namespace, a table and a view in the same schema cannot have the same name. However, tables and indexes are in different namespaces. Therefore, a table and an index in the same schema can have the same name. See Also: "Datatypes" on page 2-1, "SQL Functions" on page 5-1, and "Selecting from the DUAL Table" on page 9-15 Note: Oracle recommends that user names and passwords be encoded in ASCII or EBCDIC characters only, depending on your platform. Please refer to Oracle Database Administrator's Guide for more information about this recommendation.
- 135. Schema Object Names and Qualifiers Basic Elements of Oracle SQL 2-101 Each schema in the database has its own namespaces for the objects it contains. This means, for example, that two tables in different schemas are in different namespaces and can have the same name. Each of the following nonschema objects also has its own namespace: ■ User roles ■ Public synonyms ■ Public database links ■ Tablespaces ■ Profiles ■ Parameter files (PFILEs) and server parameter files (SPFILEs) Because the objects in these namespaces are not contained in schemas, these namespaces span the entire database. 8. Nonquoted identifiers are not case sensitive. Oracle interprets them as uppercase. Quoted identifiers are case sensitive. By enclosing names in double quotation marks, you can give the following names to different objects in the same namespace: employees "employees" "Employees" "EMPLOYEES" Note that Oracle interprets the following names the same, so they cannot be used for different objects in the same namespace: employees EMPLOYEES "EMPLOYEES" 9. Columns in the same table or view cannot have the same name. However, columns in different tables or views can have the same name. 10. Procedures or functions contained in the same package can have the same name, if their arguments are not of the same number and datatypes. Creating multiple procedures or functions with the same name in the same package with different arguments is called overloading the procedure or function. Schema Object Naming Examples The following examples are valid schema object names: last_name horse hr.hire_date "EVEN THIS & THAT!" a_very_long_and_valid_name All of these examples adhere to the rules listed in "Schema Object Naming Rules" on page 2-98. The following example is not valid, because it exceeds 30 characters: a_very_very_long_and_valid_name
- 136. Syntax for Schema Objects and Parts in SQL Statements 2-102 Oracle Database SQL Reference Although column aliases, table aliases, usernames, and passwords are not objects or parts of objects, they must also follow these naming rules unless otherwise specified in the rules themselves. Schema Object Naming Guidelines Here are several helpful guidelines for naming objects and their parts: ■ Use full, descriptive, pronounceable names (or well-known abbreviations). ■ Use consistent naming rules. ■ Use the same name to describe the same entity or attribute across tables. When naming objects, balance the objective of keeping names short and easy to use with the objective of making names as descriptive as possible. When in doubt, choose the more descriptive name, because the objects in the database may be used by many people over a period of time. Your counterpart ten years from now may have difficulty understanding a table column with a name like pmdd instead of payment_due_date. Using consistent naming rules helps users understand the part that each table plays in your application. One such rule might be to begin the names of all tables belonging to the FINANCE application with fin_. Use the same names to describe the same things across tables. For example, the department number columns of the sample employees and departments tables are both named department_id. Syntax for Schema Objects and Parts in SQL Statements This section tells you how to refer to schema objects and their parts in the context of a SQL statement. This section shows you: ■ The general syntax for referring to an object ■ How Oracle resolves a reference to an object ■ How to refer to objects in schemas other than your own ■ How to refer to objects in remote databases ■ How to refer to table and index partitions and subpartitions The following diagram shows the general syntax for referring to an object or a part: database_object_or_part::= where: ■ object is the name of the object. ■ schema is the schema containing the object. The schema qualifier lets you refer to an object in a schema other than your own. You must be granted privileges to refer to objects in other schemas. If you omit schema, then Oracle assumes that you are referring to an object in your own schema. Only schema objects can be qualified with schema. Schema objects are shown with list item 7 on page 2-100. Nonschema objects, also shown with list item 7, cannot be qualified with schema because they are not schema objects. An schema . object . part @ dblink
- 137. Syntax for Schema Objects and Parts in SQL Statements Basic Elements of Oracle SQL 2-103 exception is public synonyms, which can optionally be qualified with "PUBLIC". The quotation marks are required. ■ part is a part of the object. This identifier lets you refer to a part of a schema object, such as a column or a partition of a table. Not all types of objects have parts. ■ dblink applies only when you are using the Oracle Database distributed functionality. This is the name of the database containing the object. The dblink qualifier lets you refer to an object in a database other than your local database. If you omit dblink, then Oracle assumes that you are referring to an object in your local database. Not all SQL statements allow you to access objects on remote databases. You can include spaces around the periods separating the components of the reference to the object, but it is conventional to omit them. How Oracle Database Resolves Schema Object References When you refer to an object in a SQL statement, Oracle considers the context of the SQL statement and locates the object in the appropriate namespace. After locating the object, Oracle performs the operation specified by the statement on the object. If the named object cannot be found in the appropriate namespace, then Oracle returns an error. The following example illustrates how Oracle resolves references to objects within SQL statements. Consider this statement that adds a row of data to a table identified by the name departments: INSERT INTO departments VALUES ( 280, 'ENTERTAINMENT_CLERK', 206, 1700); Based on the context of the statement, Oracle determines that departments can be: ■ A table in your own schema ■ A view in your own schema ■ A private synonym for a table or view ■ A public synonym Oracle always attempts to resolve an object reference within the namespaces in your own schema before considering namespaces outside your schema. In this example, Oracle attempts to resolve the name departments as follows: 1. First, Oracle attempts to locate the object in the namespace in your own schema containing tables, views, and private synonyms. If the object is a private synonym, then Oracle locates the object for which the synonym stands. This object could be in your own schema, another schema, or on another database. The object could also be another synonym, in which case Oracle locates the object for which this synonym stands. 2. If the object is in the namespace, then Oracle attempts to perform the statement on the object. In this example, Oracle attempts to add the row of data to departments. If the object is not of the correct type for the statement, then Oracle returns an error. In this example, departments must be a table, view, or a private synonym resolving to a table or view. If departments is a sequence, then Oracle returns an error. 3. If the object is not in any namespace searched in thus far, then Oracle searches the namespace containing public synonyms. If the object is in that namespace, then
- 138. Syntax for Schema Objects and Parts in SQL Statements 2-104 Oracle Database SQL Reference Oracle attempts to perform the statement on it. If the object is not of the correct type for the statement, then Oracle returns an error. In this example, if departments is a public synonym for a sequence, then Oracle returns an error. If a public synonym has any dependent tables or user-defined types, then you cannot create an object with the same name as the synonym in the same schema as the dependent objects. If a synonym does not have any dependent tables or user-defined types, then you can create an object with the same name in the same schema as the dependent objects. Oracle invalidates any dependent objects and attempts to revalidate them when they are next accessed. Referring to Objects in Other Schemas To refer to objects in schemas other than your own, prefix the object name with the schema name: schema.object For example, this statement drops the employees table in the sample schema hr: DROP TABLE hr.employees Referring to Objects in Remote Databases To refer to objects in databases other than your local database, follow the object name with the name of the database link to that database. A database link is a schema object that causes Oracle to connect to a remote database to access an object there. This section tells you: ■ How to create database links ■ How to use database links in your SQL statements Creating Database Links You create a database link with the statement CREATE DATABASE LINK on page 14-31. The statement lets you specify this information about the database link: ■ The name of the database link ■ The database connect string to access the remote database ■ The username and password to connect to the remote database Oracle stores this information in the data dictionary. Database Link Names When you create a database link, you must specify its name. Database link names are different from names of other types of objects. They can be as long as 128 bytes and can contain periods (.) and the "at" sign (@). The name that you give to a database link must correspond to the name of the database to which the database link refers and the location of that database in the hierarchy of database names. The following syntax diagram shows the form of the name of a database link: See Also: Oracle Database PL/SQL User's Guide and Reference for information about how PL/SQL resolves identifier names
- 139. Syntax for Schema Objects and Parts in SQL Statements Basic Elements of Oracle SQL 2-105 dblink::= where: ■ database should specify the name portion of the global name of the remote database to which the database link connects. This global name is stored in the data dictionary of the remote database; you can see this name in the GLOBAL_ NAME data dictionary view. ■ domain should specify the domain portion of the global name of the remote database to which the database link connects. If you omit domain from the name of a database link, then Oracle qualifies the database link name with the domain of your local database as it currently exists in the data dictionary. ■ connect_descriptor lets you further qualify a database link. Using connect descriptors, you can create multiple database links to the same database. For example, you can use connect descriptors to create multiple database links to different instances of the Real Application Clusters that access the same database. The combination database.domain is sometimes called the service name. Username and Password Oracle uses the username and password to connect to the remote database. The username and password for a database link are optional. Database Connect String The database connect string is the specification used by Oracle Net to access the remote database. For information on writing database connect strings, see the Oracle Net documentation for your specific network protocol. The database string for a database link is optional. Referring to Database Links Database links are available only if you are using Oracle distributed functionality. When you issue a SQL statement that contains a database link, you can specify the database link name in one of these forms: ■ The complete database link name as stored in the data dictionary, including the database, domain, and optional connect_descriptor components. ■ The partial database link name is the database and optional connect_ descriptor components, but not the domain component. Oracle performs these tasks before connecting to the remote database: 1. If the database link name specified in the statement is partial, then Oracle expands the name to contain the domain of the local database as found in the global database name stored in the data dictionary. (You can see the current global database name in the GLOBAL_NAME data dictionary view.) 2. Oracle first searches for a private database link in your own schema with the same name as the database link in the statement. Then, if necessary, it searches for a public database link with the same name. ■ Oracle always determines the username and password from the first matching database link (either private or public). If the first matching database link has an associated username and password, then Oracle uses it. If it does not have See Also: Oracle Database Net Services Administrator's Guide database . domain @ connect_descriptor
- 140. Syntax for Schema Objects and Parts in SQL Statements 2-106 Oracle Database SQL Reference an associated username and password, then Oracle uses your current username and password. ■ If the first matching database link has an associated database string, then Oracle uses it. Otherwise Oracle searches for the next matching (public) database link. If no matching database link is found, or if no matching link has an associated database string, then Oracle returns an error. 3. Oracle uses the database string to access the remote database. After accessing the remote database, if the value of the GLOBAL_NAMES parameter is true, then Oracle verifies that the database.domain portion of the database link name matches the complete global name of the remote database. If this condition is true, then Oracle proceeds with the connection, using the username and password chosen in Step 2. If not, Oracle returns an error. 4. If the connection using the database string, username, and password is successful, then Oracle attempts to access the specified object on the remote database using the rules for resolving object references and referring to objects in other schemas discussed earlier in this section. You can disable the requirement that the database.domain portion of the database link name must match the complete global name of the remote database by setting to false the initialization parameter GLOBAL_NAMES or the GLOBAL_NAMES parameter of the ALTER SYSTEM or ALTER SESSION statement. Referring to Partitioned Tables and Indexes Tables and indexes can be partitioned. When partitioned, these schema objects consist of a number of parts called partitions, all of which have the same logical attributes. For example, all partitions in a table share the same column and constraint definitions, and all partitions in an index share the same index columns. Partition-extended and subpartition-extended names let you perform some partition-level and subpartition-level operations, such as deleting all rows from a partition or subpartition, on only one partition or subpartition. Without extended names, such operations would require that you specify a predicate (WHERE clause). For range- and list-partitioned tables, trying to phrase a partition-level operation with a predicate can be cumbersome, especially when the range partitioning key uses more than one column. For hash partitions and subpartitions, using a predicate is more difficult still, because these partitions and subpartitions are based on a system-defined hash function. Partition-extended names let you use partitions as if they were tables. An advantage of this method, which is most useful for range-partitioned tables, is that you can build partition-level access control mechanisms by granting (or revoking) privileges on these views to (or from) other users or roles.To use a partition as a table, create a view by selecting data from a single partition, and then use the view as a table. You can specify partition-extended or subpartition-extended table names for the following DML statements: ■ DELETE ■ INSERT ■ LOCK TABLE ■ SELECT See Also: Oracle Database Administrator's Guide for more information on remote name resolution
- 141. Syntax for Schema Objects and Parts in SQL Statements Basic Elements of Oracle SQL 2-107 ■ UPDATE Syntax The basic syntax for using partition-extended and subpartition-extended table names is: partition_extended_name::= Restrictions on Extended Names Currently, the use of partition-extended and subpartition-extended table names has the following restrictions: ■ No remote tables: A partition-extended or subpartition-extended table name cannot contain a database link (dblink) or a synonym that translates to a table with a dblink. To use remote partitions and subpartitions, create a view at the remote site that uses the extended table name syntax and then refer to the remote view. ■ No synonyms: A partition or subpartition extension must be specified with a base table. You cannot use synonyms, views, or any other objects. Example In the following statement, sales is a partitioned table with partition sales_q1_2000. You can create a view of the single partition sales_q1_2000, and then use it as if it were a table. This example deletes rows from the partition. CREATE VIEW Q1_2000_sales AS SELECT * FROM sales PARTITION (SALES_Q1_2000); DELETE FROM Q1_2000_sales WHERE amount_sold < 0; Referring to Object Type Attributes and Methods To refer to object type attributes or methods in a SQL statement, you must fully qualify the reference with a table alias. Consider the following example from the sample schema oe, which contains a type cust_address_typ and a table customers with a cust_address column based on the cust_address_typ: CREATE TYPE cust_address_typ OID '82A4AF6A4CD1656DE034080020E0EE3D' AS OBJECT ( street_address VARCHAR2(40) , postal_code VARCHAR2(10) , city VARCHAR2(30) , state_province VARCHAR2(10) , country_id CHAR(2) ); / CREATE TABLE customers ( customer_id NUMBER(6) , cust_first_name VARCHAR2(20) CONSTRAINT cust_fname_nn NOT NULL , cust_last_name VARCHAR2(20) CONSTRAINT cust_lname_nn NOT NULL , cust_address cust_address_typ . . . schema . table view PARTITION ( partition ) SUBPARTITION ( subpartition )
- 142. Syntax for Schema Objects and Parts in SQL Statements 2-108 Oracle Database SQL Reference In a SQL statement, reference to the postal_code attribute must be fully qualified using a table alias, as illustrated in the following example: SELECT c.cust_address.postal_code FROM customers c; UPDATE customers c SET c.cust_address.postal_code = 'GU13 BE5' WHERE c.cust_address.city = 'Fleet'; To reference a member method that does not accept arguments, you must provide empty parentheses. For example, the sample schema oe contains an object table categories_tab, based on catalog_typ, which contains the member function getCatalogName. In order to call this method in a SQL statement, you must provide empty parentheses as shown in this example: SELECT TREAT(VALUE(c) AS catalog_typ).getCatalogName() "Catalog Type" FROM categories_tab c WHERE category_id = 90; Catalog Type ------------------------------------ online catalog See Also: Oracle Database Concepts for more information on user-defined datatypes
- 143. Pseudocolumns 3-1 3 Pseudocolumns A pseudocolumn behaves like a table column, but is not actually stored in the table. You can select from pseudocolumns, but you cannot insert, update, or delete their values. A pseudocolumn is also similar to a function without arguments (please refer to Chapter 5, "Functions". However, functions without arguments typically return the same value for every row in the result set, whereas pseudocolumns typically return a different value for each row. This chapter contains the following sections: ■ Hierarchical Query Pseudocolumns ■ Sequence Pseudocolumns ■ Version Query Pseudocolumns ■ COLUMN_VALUE Pseudocolumn ■ OBJECT_ID Pseudocolumn ■ OBJECT_VALUE Pseudocolumn ■ ORA_ROWSCN Pseudocolumn ■ ROWID Pseudocolumn ■ ROWNUM Pseudocolumn ■ XMLDATA Pseudocolumn Hierarchical Query Pseudocolumns The hierarchical query pseudocolumns are valid only in hierarchical queries. The hierarchical query pseudocolumns are: ■ CONNECT_BY_ISCYCLE Pseudocolumn ■ CONNECT_BY_ISLEAF Pseudocolumn ■ LEVEL Pseudocolumn CONNECT_BY_ISCYCLE Pseudocolumn The CONNECT_BY_ISCYCLE pseudocolumn returns 1 if the current row has a child which is also its ancestor. Otherwise it returns 0. You can specify CONNECT_BY_ISCYCLE only if you have specified the NOCYCLE parameter of the CONNECT BY clause. NOCYCLE enables Oracle to return the results of a query that would otherwise fail because of a CONNECT BY loop in the data.
- 144. Hierarchical Query Pseudocolumns 3-2 Oracle Database SQL Reference CONNECT_BY_ISLEAF Pseudocolumn The CONNECT_BY_ISLEAF pseudocolumn returns 1 if the current row is a leaf of the tree defined by the CONNECT BY condition. Otherwise it returns 0. This information indicates whether a given row can be further expanded to show more of the hierarchy. CONNECT_BY_ISLEAF Example The following example shows the first three levels of the hr.employees table, indicating for each row whether it is a leaf row (indicated by 1 in the IsLeaf column) or whether it has child rows (indicated by 0 in the IsLeaf column): SELECT last_name "Employee", CONNECT_BY_ISLEAF "IsLeaf", LEVEL, SYS_CONNECT_BY_PATH(last_name, '/') "Path" FROM employees WHERE LEVEL <= 3 AND department_id = 80 START WITH employee_id = 100 CONNECT BY PRIOR employee_id = manager_id AND LEVEL <= 4; Employee IsLeaf LEVEL Path --------------- ---------- ---------- ----------------------------------- Russell 0 2 /King/Russell Tucker 1 3 /King/Russell/Tucker Bernstein 1 3 /King/Russell/Bernstein Hall 1 3 /King/Russell/Hall Olsen 1 3 /King/Russell/Olsen Cambrault 1 3 /King/Russell/Cambrault Tuvault 1 3 /King/Russell/Tuvault Partners 0 2 /King/Partners King 1 3 /King/Partners/King Sully 1 3 /King/Partners/Sully McEwen 1 3 /King/Partners/McEwen Smith 1 3 /King/Partners/Smith Doran 1 3 /King/Partners/Doran Sewall 1 3 /King/Partners/Sewall Errazuriz 0 2 /King/Errazuriz Vishney 1 3 /King/Errazuriz/Vishney ... 34 rows selected. LEVEL Pseudocolumn For each row returned by a hierarchical query, the LEVEL pseudocolumn returns 1 for a root row, 2 for a child of a root, and so on. A root row is the highest row within an inverted tree. A child row is any nonroot row. A parent row is any row that has children. A leaf row is any row without children. Figure 3–1 shows the nodes of an inverted tree with their LEVEL values. See Also: "Hierarchical Queries" on page 9-2 for more information about the NOCYCLE parameter and "Hierarchical Query Examples" on page 9-5 for an example that uses the CONNECT_BY_ISCYCLE pseudocolumn See Also: "Hierarchical Queries" on page 9-2 and SYS_CONNECT_ BY_PATH on page 5-176
- 145. Sequence Pseudocolumns Pseudocolumns 3-3 Figure 3–1 Hierarchical Tree To define a hierarchical relationship in a query, you must use the START WITH and CONNECT BY clauses. Sequence Pseudocolumns A sequence is a schema object that can generate unique sequential values. These values are often used for primary and unique keys. You can refer to sequence values in SQL statements with these pseudocolumns: ■ CURRVAL: Returns the current value of a sequence ■ NEXTVAL: Increments the sequence and returns the next value You must qualify CURRVAL and NEXTVAL with the name of the sequence: sequence.CURRVAL sequence.NEXTVAL To refer to the current or next value of a sequence in the schema of another user, you must have been granted either SELECT object privilege on the sequence or SELECT ANY SEQUENCE system privilege, and you must qualify the sequence with the schema containing it: schema.sequence.CURRVAL schema.sequence.NEXTVAL To refer to the value of a sequence on a remote database, you must qualify the sequence with a complete or partial name of a database link: schema.sequence.CURRVAL@dblink schema.sequence.NEXTVAL@dblink Where to Use Sequence Values You can use CURRVAL and NEXTVAL in the following locations: See Also: "Hierarchical Queries" on page 9-2 for information on hierarchical queries in general and "IN Condition" on page 7-21 for restrictions on using the LEVEL pseudocolumn See Also: "Referring to Objects in Remote Databases" on page 2-104 for more information on referring to database links Level 1 Level 2 Level 3 Level 4 child/ leaf parent/ child root/ parent parent/ child child/ leaf child/ leaf child/ leaf child/ leaf parent/ child parent/ child
- 146. Sequence Pseudocolumns 3-4 Oracle Database SQL Reference ■ The select list of a SELECT statement that is not contained in a subquery, materialized view, or view ■ The select list of a subquery in an INSERT statement ■ The VALUES clause of an INSERT statement ■ The SET clause of an UPDATE statement Restrictions on Sequence Values You cannot use CURRVAL and NEXTVAL in the following constructs: ■ A subquery in a DELETE, SELECT, or UPDATE statement ■ A query of a view or of a materialized view ■ A SELECT statement with the DISTINCT operator ■ A SELECT statement with a GROUP BY clause or ORDER BY clause ■ A SELECT statement that is combined with another SELECT statement with the UNION, INTERSECT, or MINUS set operator ■ The WHERE clause of a SELECT statement ■ The DEFAULT value of a column in a CREATE TABLE or ALTER TABLE statement ■ The condition of a CHECK constraint Within a single SQL statement that uses CURRVAL or NEXTVAL, all referenced LONG columns, updated tables, and locked tables must be located on the same database. How to Use Sequence Values When you create a sequence, you can define its initial value and the increment between its values. The first reference to NEXTVAL returns the initial value of the sequence. Subsequent references to NEXTVAL increment the sequence value by the defined increment and return the new value. Any reference to CURRVAL always returns the current value of the sequence, which is the value returned by the last reference to NEXTVAL. Before you use CURRVAL for a sequence in your session, you must first initialize the sequence with NEXTVAL. Please refer to CREATE SEQUENCE on page 15-71 for information on sequences. Within a single SQL statement containing a reference to NEXTVAL, Oracle increments the sequence once: ■ For each row returned by the outer query block of a SELECT statement. Such a query block can appear in the following places: – A top-level SELECT statement – An INSERT ... SELECT statement (either single-table or multitable). For a multitable insert, the reference to NEXTVAL must appear in the VALUES clause, and the sequence is updated once for each row returned by the subquery, even though NEXTVAL may be referenced in multiple branches of the multitable insert. – A CREATE TABLE ... AS SELECT statement – A CREATE MATERIALIZED VIEW ... AS SELECT statement ■ For each row updated in an UPDATE statement ■ For each INSERT statement containing a VALUES clause
- 147. Version Query Pseudocolumns Pseudocolumns 3-5 ■ For each row merged by a MERGE statement. The reference to NEXTVAL can appear in the merge_insert_clause or the merge_update_clause or both. The NEXTVALUE value is incremented for each row updated and for each row inserted, even if the sequence number is not actually used in the update or insert operation. If NEXTVAL is specified more than once in any of these locations, then the sequence is incremented once for each row and returns the same value for all occurrences of NEXTVAL for that row. If any of these locations contains more than one reference to NEXTVAL, then Oracle increments the sequence once and returns the same value for all occurrences of NEXTVAL. If any of these locations contains references to both CURRVAL and NEXTVAL, then Oracle increments the sequence and returns the same value for both CURRVAL and NEXTVAL. A sequence can be accessed by many users concurrently with no waiting or locking. Finding the next value of a sequence: Example This example selects the next value of the employee sequence in the sample schema hr: SELECT employees_seq.nextval FROM DUAL; Inserting sequence values into a table: Example This example increments the employee sequence and uses its value for a new employee inserted into the sample table hr.employees: INSERT INTO employees VALUES (employees_seq.nextval, 'John', 'Doe', 'jdoe', '555-1212', TO_DATE(SYSDATE), 'PU_CLERK', 2500, null, null, 30); Reusing the current value of a sequence: Example This example adds a new order with the next order number to the master order table. It then adds suborders with this number to the detail order table: INSERT INTO orders (order_id, order_date, customer_id) VALUES (orders_seq.nextval, TO_DATE(SYSDATE), 106); INSERT INTO order_items (order_id, line_item_id, product_id) VALUES (orders_seq.currval, 1, 2359); INSERT INTO order_items (order_id, line_item_id, product_id) VALUES (orders_seq.currval, 2, 3290); INSERT INTO order_items (order_id, line_item_id, product_id) VALUES (orders_seq.currval, 3, 2381); Version Query Pseudocolumns The version query pseudocolumns are valid only in Oracle Flashback Version Query, which is a form of Oracle Flashback Query. The version query pseudocolumns are: ■ VERSIONS_STARTTIME: Returns the timestamp of the first version of the rows returned by the query. ■ VERSIONS_STARTSCN: Returns the SCN of the first version of the rows returned by the query.
- 148. COLUMN_VALUE Pseudocolumn 3-6 Oracle Database SQL Reference ■ VERSIONS_ENDTIME: Returns the timestamp of the last version of the rows returned by the query. ■ VERSIONS_ENDSCN: Returns the SCN of the last version of the rows returned by the query. ■ VERSIONS_XID: For each version of each row, returns the transaction ID (a RAW number) of the transaction that created that row version. ■ VERSIONS_OPERATION: For each version of each row, returns a single character representing the operation that caused that row version. The values returned are I (for an insert operation), U (for an update operation) or D (for a delete operation). COLUMN_VALUE Pseudocolumn When you refer to an XMLTable construct without the COLUMNS clause, or when you use the TABLE function to refer to a scalar nested table type, the database returns a virtual table with a single column. This name of this pseudocolumn is COLUMN_ VALUE. In the context of XMLTable, the value returned is of datatype XMLType. For example, the following two statements are equivalent, and the output for both shows COLUMN_ VALUE as the name of the column being returned: SELECT * FROM XMLTABLE(’<a>123</a>’); COLUMN_VALUE --------------------------------------- <a>123</a> SELECT COLUMN_VALUE FROM (XMLTable(’<a>123</a>’)); COLUMN_VALUE ---------------------------------------- <a>123</a> In the context of a TABLE function, the value returned is the datatype of the collection element. The following statements create the two levels of nested tables illustrated in "Multi-level Collection Example" on page 16-52 to show the uses of COLUMN_VALUE in this context: CREATE TYPE phone AS TABLE OF NUMBER; / CREATE TYPE phone_list AS TABLE OF phone; / The next statement uses COLUMN_VALUE to select from the phone type: SELECT t.COLUMN_VALUE from table(phone(1,2,3)) t; COLUMN_VALUE ------------ 1 2 3 In a nested type, you can use the COLUMN_VALUE pseudocolumn in both the select list and the TABLE function: See Also: flashback_query_clause on page 19-14 for more information on version queries
- 149. OBJECT_VALUE Pseudocolumn Pseudocolumns 3-7 SELECT t.COLUMN_VALUE FROM TABLE(phone_list(phone(1,2,3))) p, TABLE(p.COLUMN_VALUE) t; COLUMN_VALUE ------------ 1 2 3 The keyword COLUMN_VALUE is also the name that Oracle Database generates for the scalar value of an inner nested table without a column or attribute name, as shown in the example that follows. In this context, COLUMN_VALUE is not a pseudocolumn, but an actual column name. CREATE TABLE my_customers ( cust_id NUMBER, name VARCHAR2(25), phone_numbers phone_list, credit_limit NUMBER) NESTED TABLE phone_numbers STORE AS outer_ntab (NESTED TABLE COLUMN_VALUE STORE AS inner_ntab); OBJECT_ID Pseudocolumn The OBJECT_ID pseudocolumn returns the object identifier of a column of an object table or view. Oracle uses this pseudocolumn as the primary key of an object table. OBJECT_ID is useful in INSTEAD OF triggers on views and for identifying the ID of a substitutable row in an object table. OBJECT_VALUE Pseudocolumn The OBJECT_VALUE pseudocolumn returns system-generated names for the columns of an object table, XMLType table, object view, or XMLType view. This pseudocolumn is useful for identifying the value of a substitutable row in an object table and for creating object views with the WITH OBJECT IDENTIFIER clause. See Also: ■ XMLTABLE on page 5-232 for information on that function ■ table_collection_expression::= on page 18-53 for information on the TABLE function ■ ALTER TABLE examples in "Nested Tables: Examples" on page 12-76 Note: In earlier releases, this pseudocolumn was called SYS_NC_ OID$. That name is still supported for backward compatibility. However, Oracle recommends that you use the more intuitive name OBJECT_ID. See Also: Oracle Database Application Developer's Guide - Object-Relational Features for examples of the use of this pseudocolumn
- 150. ORA_ROWSCN Pseudocolumn 3-8 Oracle Database SQL Reference ORA_ROWSCN Pseudocolumn For each row, ORA_ROWSCN returns the conservative upper bound system change number (SCN) of the most recent change to the row. This pseudocolumn is useful for determining approximately when a row was last updated. It is not absolutely precise, because Oracle tracks SCNs by transaction committed for the block in which the row resides. You can obtain a more fine-grained approximation of the SCN by creating your tables with row-level dependency tracking. Please refer to CREATE TABLE ... NOROWDEPENDENCIES | ROWDEPENDENCIES on page 16-44 for more information on row-level dependency tracking. You cannot use this pseudocolumn in a query to a view. However, you can use it to refer to the underlying table when creating a view. You can also use this pseudocolumn in the WHERE clause of an UPDATE or DELETE statement. ORA_ROWSCN is not supported for Flashback Query. Instead, use the version query pseudocolumns, which are provided explicitly for Flashback Query. Please refer to the SELECT ... flashback_query_clause on page 19-14 for information on Flashback Query and "Version Query Pseudocolumns" on page 3-5 for additional information on those pseudocolumns. Restriction: This pseudocolumn is not supported for external tables. Example The first statement below uses the ORA_ROWSCN pseudocolumn to get the system change number of the last operation on the employees table. The second statement uses the pseudocolumn with the SCN_TO_TIMESTAMP function to determine the timestamp of the operation: SELECT ORA_ROWSCN, last_name FROM employees WHERE employee_id = 188; SELECT SCN_TO_TIMESTAMP(ORA_ROWSCN), last_name FROM employees WHERE employee_id = 188; ROWID Pseudocolumn For each row in the database, the ROWID pseudocolumn returns the address of the row. Oracle Database rowid values contain information necessary to locate a row: ■ The data object number of the object ■ The data block in the datafile in which the row resides ■ The position of the row in the data block (first row is 0) Note: In earlier releases, this pseudocolumn was called SYS_NC_ ROWINFO$. That name is still supported for backward compatibility. However, Oracle recommends that you use the more intuitive name OBJECT_VALUE. See Also: ■ object_table on page 16-48 and object_view_clause on page 17-35 for more information on the use of this pseudocolumn ■ Oracle Database Application Developer's Guide - Object-Relational Features for examples of the use of this pseudocolumn See Also: SCN_TO_TIMESTAMP on page 5-153
- 151. ROWNUM Pseudocolumn Pseudocolumns 3-9 ■ The datafile in which the row resides (first file is 1). The file number is relative to the tablespace. Usually, a rowid value uniquely identifies a row in the database. However, rows in different tables that are stored together in the same cluster can have the same rowid. Values of the ROWID pseudocolumn have the datatype ROWID or UROWID. Please refer to "ROWID Datatype" on page 2-27 and "UROWID Datatype" on page 2-28 for more information. Rowid values have several important uses: ■ They are the fastest way to access a single row. ■ They can show you how the rows in a table are stored. ■ They are unique identifiers for rows in a table. You should not use ROWID as the primary key of a table. If you delete and reinsert a row with the Import and Export utilities, for example, then its rowid may change. If you delete a row, then Oracle may reassign its rowid to a new row inserted later. Although you can use the ROWID pseudocolumn in the SELECT and WHERE clause of a query, these pseudocolumn values are not actually stored in the database. You cannot insert, update, or delete a value of the ROWID pseudocolumn. Example This statement selects the address of all rows that contain data for employees in department 20: SELECT ROWID, last_name FROM employees WHERE department_id = 20; ROWNUM Pseudocolumn For each row returned by a query, the ROWNUM pseudocolumn returns a number indicating the order in which Oracle selects the row from a table or set of joined rows. The first row selected has a ROWNUM of 1, the second has 2, and so on. You can use ROWNUM to limit the number of rows returned by a query, as in this example: SELECT * FROM employees WHERE ROWNUM < 10; If an ORDER BY clause follows ROWNUM in the same query, then the rows will be reordered by the ORDER BY clause. The results can vary depending on the way the rows are accessed. For example, if the ORDER BY clause causes Oracle to use an index to access the data, then Oracle may retrieve the rows in a different order than without the index. Therefore, the following statement will not have the same effect as the preceding example: SELECT * FROM employees WHERE ROWNUM < 11 ORDER BY last_name; If you embed the ORDER BY clause in a subquery and place the ROWNUM condition in the top-level query, then you can force the ROWNUM condition to be applied after the ordering of the rows. For example, the following query returns the employees with the 10 smallest employee numbers. This is sometimes referred to as top-N reporting: SELECT * FROM (SELECT * FROM employees ORDER BY employee_id) WHERE ROWNUM < 11;
- 152. XMLDATA Pseudocolumn 3-10 Oracle Database SQL Reference In the preceding example, the ROWNUM values are those of the top-level SELECT statement, so they are generated after the rows have already been ordered by employee_id in the subquery. Conditions testing for ROWNUM values greater than a positive integer are always false. For example, this query returns no rows: SELECT * FROM employees WHERE ROWNUM > 1; The first row fetched is assigned a ROWNUM of 1 and makes the condition false. The second row to be fetched is now the first row and is also assigned a ROWNUM of 1 and makes the condition false. All rows subsequently fail to satisfy the condition, so no rows are returned. You can also use ROWNUM to assign unique values to each row of a table, as in this example: UPDATE my_table SET column1 = ROWNUM; Please refer to the function ROW_NUMBER on page 5-150 for an alternative method of assigning unique numbers to rows. XMLDATA Pseudocolumn Oracle stores XMLType data either in LOB or object-relational columns, based on XMLSchema information and how you specify the storage clause. The XMLDATA pseudocolumn lets you access the underlying LOB or object relational column to specify additional storage clause parameters, constraints, indexes, and so forth. Example The following statements illustrate the use of this pseudocolumn. Suppose you create a simple table of XMLType: CREATE TABLE xml_lob_tab of XMLTYPE; The default storage is in a CLOB column. To change the storage characteristics of the underlying LOB column, you can use the following statement: ALTER TABLE xml_lob_tab MODIFY LOB (XMLDATA) (STORAGE (BUFFER_POOL DEFAULT) CACHE); Now suppose you have created an XMLSchema-based table like the xwarehouses table created in "Using XML in SQL Statements" on page E-8. You could then use the XMLDATA column to set the properties of the underlying columns, as shown in the following statement: ALTER TABLE xwarehouses ADD (UNIQUE(XMLDATA."WarehouseId")); Note: Using ROWNUM in a query can affect view optimization. For more information, see Oracle Database Concepts.
- 153. Operators 4-1 4 Operators An operator manipulates data items and returns a result. Syntactically, an operator appears before or after an operand or between two operands. This chapter contains these sections: ■ About SQL Operators ■ Arithmetic Operators ■ Concatenation Operator ■ Hierarchical Query Operators ■ Set Operators ■ Multiset Operators ■ User-Defined Operators This chapter discusses nonlogical (non-Boolean) operators. These operators cannot by themselves serve as the condition of a WHERE or HAVING clause in queries or subqueries. For information on logical operators, which serve as conditions, please refer to Chapter 7, "Conditions". About SQL Operators Operators manipulate individual data items called operands or arguments. Operators are represented by special characters or by keywords. For example, the multiplication operator is represented by an asterisk (*). If you have installed Oracle Text, then you can use the SCORE operator, which is part of that product, in Oracle Text queries. You can also create conditions with the built-in Text operators, including CONTAINS, CATSEARCH, and MATCHES. For more information on these Oracle Text elements, please refer to Oracle Text Reference. If you are using Oracle Expression Filter, then you can create conditions with the built-in EVALUATE operator that is part of that product. For more information, please refer to Oracle Database Application Developer's Guide - Rules Manager and Expression Filter.
- 154. About SQL Operators 4-2 Oracle Database SQL Reference Unary and Binary Operators The two general classes of operators are: ■ unary: A unary operator operates on only one operand. A unary operator typically appears with its operand in this format: operator operand ■ binary: A binary operator operates on two operands. A binary operator appears with its operands in this format: operand1 operator operand2 Other operators with special formats accept more than two operands. If an operator is given a null operand, the result is always null. The only operator that does not follow this rule is concatenation (||). Operator Precedence Precedence is the order in which Oracle Database evaluates different operators in the same expression. When evaluating an expression containing multiple operators, Oracle evaluates operators with higher precedence before evaluating those with lower precedence. Oracle evaluates operators with equal precedence from left to right within an expression. Table 4–1 lists the levels of precedence among SQL operators from high to low. Operators listed on the same line have the same precedence. Precedence Example In the following expression, multiplication has a higher precedence than addition, so Oracle first multiplies 2 by 3 and then adds the result to 1. 1+2*3 Note: The combined values of the NLS_COMP and NLS_SORT settings determine the rules by which characters are sorted and compared. If NLS_COMP is set to LINGUISTIC for your database, then all entities in this chapter will be interpreted according to the rules specified by the NLS_SORT parameter. If NLS_COMP is not set to LINGUISTIC, then the functions are interpreted without regard to the NLS_SORT setting. NLS_SORT can be explicitly set. If it is not set explicitly, it is derived from NLS_LANGUAGE. Please refer to Oracle Database Globalization Support Guide for more information on these settings. Table 4–1 SQL Operator Precedence Operator Operation +, - (as unary operators), PRIOR, CONNECT_ BY_ROOT identity, negation, location in hierarchy *, / multiplication, division +, - (as binary operators), || addition, subtraction, concatenation SQL conditions are evaluated after SQL operators See "Condition Precedence" on page 7-3
- 155. Concatenation Operator Operators 4-3 You can use parentheses in an expression to override operator precedence. Oracle evaluates expressions inside parentheses before evaluating those outside. SQL also supports set operators (UNION, UNION ALL, INTERSECT, and MINUS), which combine sets of rows returned by queries, rather than individual data items. All set operators have equal precedence. Arithmetic Operators You can use an arithmetic operator with one or two arguments to negate, add, subtract, multiply, and divide numeric values. Some of these operators are also used in datetime and interval arithmetic. The arguments to the operator must resolve to numeric datatypes or to any datatype that can be implicitly converted to a numeric datatype. Unary arithmetic operators return the same datatype as the numeric datatype of the argument. For binary arithmetic operators, Oracle determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype, and returns that datatype. Table 4–2 lists arithmetic operators. Do not use two consecutive minus signs (--) in arithmetic expressions to indicate double negation or the subtraction of a negative value. The characters -- are used to begin comments within SQL statements. You should separate consecutive minus signs with a space or parentheses. Please refer to "Comments" on page 2-70 for more information on comments within SQL statements. Concatenation Operator The concatenation operator manipulates character strings and CLOB data. Table 4–3 describes the concatenation operator. See Also: "Hierarchical Query Operators" on page 4-5 and "Hierarchical Queries" on page 9-2 for information on the PRIOR operator, which is used only in hierarchical queries See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion, "Numeric Precedence" on page 2-13 for information on numeric precedence, and "Datetime/Interval Arithmetic" on page 2-19 Table 4–2 Arithmetic Operators Operator Purpose Example + - When these denote a positive or negative expression, they are unary operators. SELECT * FROM order_items WHERE quantity = -1; SELECT * FROM employees WHERE -salary < 0; + - When they add or subtract, they are binary operators. SELECT hire_date FROM employees WHERE SYSDATE - hire_date > 365; * / Multiply, divide. These are binary operators. UPDATE employees SET salary = salary * 1.1;
- 156. Concatenation Operator 4-4 Oracle Database SQL Reference The result of concatenating two character strings is another character string. If both character strings are of datatype CHAR, the result has datatype CHAR and is limited to 2000 characters. If either string is of datatype VARCHAR2, the result has datatype VARCHAR2 and is limited to 4000 characters. If either argument is a CLOB, the result is a temporary CLOB. Trailing blanks in character strings are preserved by concatenation, regardless of the datatypes of the string or CLOB. On most platforms, the concatenation operator is two solid vertical bars, as shown in Table 4–3. However, some IBM platforms use broken vertical bars for this operator. When moving SQL script files between systems having different character sets, such as between ASCII and EBCDIC, vertical bars might not be translated into the vertical bar required by the target Oracle Database environment. Oracle provides the CONCAT character function as an alternative to the vertical bar operator for cases when it is difficult or impossible to control translation performed by operating system or network utilities. Use this function in applications that will be moved between environments with differing character sets. Although Oracle treats zero-length character strings as nulls, concatenating a zero-length character string with another operand always results in the other operand, so null can result only from the concatenation of two null strings. However, this may not continue to be true in future versions of Oracle Database. To concatenate an expression that might be null, use the NVL function to explicitly convert the expression to a zero-length string. Concatenation Example This example creates a table with both CHAR and VARCHAR2 columns, inserts values both with and without trailing blanks, and then selects these values and concatenates them. Note that for both CHAR and VARCHAR2 columns, the trailing blanks are preserved. CREATE TABLE tab1 (col1 VARCHAR2(6), col2 CHAR(6), col3 VARCHAR2(6), col4 CHAR(6) ); INSERT INTO tab1 (col1, col2, col3, col4) VALUES ('abc', 'def ', 'ghi ', 'jkl'); SELECT col1||col2||col3||col4 "Concatenation" FROM tab1; Concatenation ------------------------ abcdef ghi jkl Table 4–3 Concatenation Operator Operator Purpose Example || Concatenates character strings and CLOB data. SELECT 'Name is ' || last_name FROM employees; See Also: ■ "Character Datatypes" on page 2-8 for more information on the differences between the CHAR and VARCHAR2 datatypes ■ The functions CONCAT on page 5-36 and NVL on page 5-110 ■ Oracle Database Application Developer's Guide - Large Objects for more information about CLOBs
- 157. Multiset Operators Operators 4-5 Hierarchical Query Operators Two operators, PRIOR and CONNECT_BY_ROOT, are valid only in hierarchical queries. PRIOR In a hierarchical query, one expression in the CONNECT BY condition must be qualified by the PRIOR operator. If the CONNECT BY condition is compound, then only one condition requires the PRIOR operator, although you can have multiple PRIOR conditions. PRIOR evaluates the immediately following expression for the parent row of the current row in a hierarchical query. PRIOR is most commonly used when comparing column values with the equality operator. (The PRIOR keyword can be on either side of the operator.) PRIOR causes Oracle to use the value of the parent row in the column. Operators other than the equal sign (=) are theoretically possible in CONNECT BY clauses. However, the conditions created by these other operators can result in an infinite loop through the possible combinations. In this case Oracle detects the loop at run time and returns an error. Please refer to "Hierarchical Queries" on page 9-2 for more information on this operator, including examples. CONNECT_BY_ROOT CONNECT_BY_ROOT is a unary operator that is valid only in hierarchical queries. When you qualify a column with this operator, Oracle returns the column value using data from the root row. This operator extends the functionality of the CONNECT BY [PRIOR] condition of hierarchical queries. Restriction on CONNECT_BY_ROOT You cannot specify this operator in the START WITH condition or the CONNECT BY condition. Set Operators Set operators combine the results of two component queries into a single result. Queries containing set operators are called compound queries. Table 4–4 lists SQL set operators. They are fully described, including examples and restrictions on these operators, in "The UNION [ALL], INTERSECT, MINUS Operators" on page 9-7. Multiset Operators Multiset operators combine the results of two nested tables into a single nested table. The examples related to multiset operators require that two nested tables be created and loaded with data as follows: See Also: "CONNECT_BY_ROOT Examples" on page 9-6 Table 4–4 Set Operators Operator Returns UNION All distinct rows selected by either query UNION ALL All rows selected by either query, including all duplicates INTERSECT All distinct rows selected by both queries MINUS All distinct rows selected by the first query but not the second
- 158. Multiset Operators 4-6 Oracle Database SQL Reference First, make a copy of the oe.customers table called customers_demo. We will add the nested table columns to customers_demo. CREATE TABLE customers_demo AS SELECT * FROM customers; Next, create a table type called cust_address_tab_typ. This type will be used when creating the nested table columns. CREATE TYPE cust_address_tab_typ AS TABLE OF cust_address_typ / Now, create two nested table columns in the customers_demo table: ALTER TABLE customers_demo ADD (cust_address_ntab cust_address_tab_typ, cust_address2_ntab cust_address_tab_typ) NESTED TABLE cust_address_ntab STORE AS cust_address_ntab_store NESTED TABLE cust_address2_ntab STORE AS cust_address2_ntab_store; Finally, load data into the two new nested table columns using data from the cust_ address column of the oe.customers table: UPDATE CUSTOMERS_DEMO cd SET cust_address_ntab = CAST(MULTISET(SELECT cust_address FROM customers c WHERE c.customer_id = cd.customer_id) as cust_address_tab_typ); UPDATE CUSTOMERS_DEMO cd SET cust_address2_ntab = CAST(MULTISET(SELECT cust_address FROM customers c WHERE c.customer_id = cd.customer_id) as cust_address_tab_typ); MULTISET EXCEPT MULTISET EXCEPT takes as arguments two nested tables and returns a nested table whose elements are in the first nested table but not in the second nested table. The two input nested tables must be of the same type, and the returned nested table is of the same type as well. ■ The ALL keyword instructs Oracle to return all elements in nested_table1 that are not in nested_table2. For example, if a particular element occurs m times in nested_table1 and n times in nested_table2, then the result will have (m-n) occurrences of the element if m >n and 0 occurrences if m<=n. ALL is the default. ■ The DISTINCT keyword instructs Oracle to eliminate any element in nested_ table1 which is also in nested_table2, regardless of the number of occurrences. nested_table1 MULTISET EXCEPT ALL DISTINCT nested_table2
- 159. Multiset Operators Operators 4-7 ■ The element types of the nested tables must be comparable. Please refer to "Comparison Conditions" on page 7-4 for information on the comparability of nonscalar types. Example The following example compares two nested tables and returns a nested table of those elements found in the first nested table but not in the second nested table: SELECT customer_id, cust_address_ntab MULTISET EXCEPT DISTINCT cust_address2_ntab multiset_except FROM customers_demo; CUSTOMER_ID MULTISET_EXCEPT(STREET_ADDRESS, POSTAL_CODE, CITY, STATE_PROVINCE, COUNTRY_ID) ----------- -------------------------------------------------------------------------------- 101 CUST_ADDRESS_TAB_TYP() 102 CUST_ADDRESS_TAB_TYP() 103 CUST_ADDRESS_TAB_TYP() 104 CUST_ADDRESS_TAB_TYP() 105 CUST_ADDRESS_TAB_TYP() . . . The preceding example requires the table customers_demo and two nested table columns containing data. Please refer to "Multiset Operators" on page 4-5 to create this table and nested table columns. MULTISET INTERSECT MULTISET INTERSECT takes as arguments two nested tables and returns a nested table whose values are common in the two input nested tables. The two input nested tables must be of the same type, and the returned nested table is of the same type as well. ■ The ALL keyword instructs Oracle to return all common occurrences of elements that are in the two input nested tables, including duplicate common values and duplicate common NULL occurrences. For example, if a particular value occurs m times in nested_table1 and n times in nested_table2, then the result would contain the element min(m,n) times. ALL is the default. ■ The DISTINCT keyword instructs Oracle to eliminate duplicates from the returned nested table, including duplicates of NULL, if they exist. ■ The element types of the nested tables must be comparable. Please refer to "Comparison Conditions" on page 7-4 for information on the comparability of nonscalar types. Example The following example compares two nested tables and returns a nested table of those elements found in both input nested tables: SELECT customer_id, cust_address_ntab MULTISET INTERSECT DISTINCT cust_address2_ntab multiset_intersect FROM customers_demo; CUSTOMER_ID MULTISET_INTERSECT(STREET_ADDRESS, POSTAL_CODE, CITY, STATE_PROVINCE, COUNTRY_ID ----------- ----------------------------------------------------------------------------------- 101 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('514 W Superior St', '46901', 'Kokomo', 'IN', 'US')) nested_table1 MULTISET INTERSECT ALL DISTINCT nested_table2
- 160. Multiset Operators 4-8 Oracle Database SQL Reference 102 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('2515 Bloyd Ave', '46218', 'Indianapolis', 'IN', 'US')) 103 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('8768 N State Rd 37', '47404', 'Bloomington', 'IN', 'US')) 104 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('6445 Bay Harbor Ln', '46254', 'Indianapolis', 'IN', 'US')) 105 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('4019 W 3Rd St', '47404', 'Bloomington', 'IN', 'US')) . . . The preceding example requires the table customers_demo and two nested table columns containing data. Please refer to "Multiset Operators" on page 4-5 to create this table and nested table columns. MULTISET UNION MULTISET UNION takes as arguments two nested tables and returns a nested table whose values are those of the two input nested tables. The two input nested tables must be of the same type, and the returned nested table is of the same type as well. ■ The ALL keyword instructs Oracle to return all elements that are in the two input nested tables, including duplicate values and duplicate NULL occurrences. This is the default. ■ The DISTINCT keyword instructs Oracle to eliminate duplicates from the returned nested table, including duplicates of NULL, if they exist. ■ The element types of the nested tables must be comparable. Please refer to "Comparison Conditions" on page 7-4 for information on the comparability of nonscalar types. Example The following example compares two nested tables and returns a nested table of elements from both input nested tables: SELECT customer_id, cust_address_ntab MULTISET UNION cust_address2_ntab multiset_union FROM customers_demo; CUSTOMER_ID MULTISET_UNION(STREET_ADDRESS, POSTAL_CODE, CITY, STATE_PROVINCE, COUNTRY_ID) ----------- ------------------------------------------------------------------------------- 101 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('514 W Superior St', '46901', 'Kokomo', 'IN', 'US'), CUST_ADDRESS_TYP('514 W Superior St', '46901', 'Kokomo', 'IN', 'US')) 102 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('2515 Bloyd Ave', '46218', 'Indianapolis', 'IN', 'US'), CUST_ADDRESS_TYP('2515 Bloyd Ave', '46218', 'Indianapolis', 'IN','US')) 103 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('8768 N State Rd 37', '47404', 'Bloomington', 'IN', 'US'), CUST_ADDRESS_TYP('8768 N State Rd 37', '47404', 'Bloomington', 'IN', 'US')) 104 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('6445 Bay Harbor Ln', '46254', 'Indianapolis', 'IN', 'US'), CUST_ADDRESS_TYP('6445 Bay Harbor Ln', '46254', 'Indianapolis', 'IN', 'US')) 105 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('4019 W 3Rd St', '47404', 'Bloomington', 'IN', 'US'), CUST_ADDRESS_TYP('4019 W 3Rd St', '47404', 'Bloomington', 'IN', 'US')) . . . The preceding example requires the table customers_demo and two nested table columns containing data. Please refer to "Multiset Operators" on page 4-5 to create this table and nested table columns. nested_table1 MULTISET UNION ALL DISTINCT nested_table2
- 161. User-Defined Operators Operators 4-9 User-Defined Operators Like built-in operators, user-defined operators take a set of operands as input and return a result. However, you create them with the CREATE OPERATOR statement, and they are identified by user-defined names. They reside in the same namespace as tables, views, types, and standalone functions. After you have defined a new operator, you can use it in SQL statements like any other built-in operator. For example, you can use user-defined operators in the select list of a SELECT statement, the condition of a WHERE clause, or in ORDER BY clauses and GROUP BY clauses. However, you must have EXECUTE privilege on the operator to do so, because it is a user-defined object. See Also: CREATE OPERATOR on page 15-32 for an example of creating an operator and Oracle Database Data Cartridge Developer's Guide for more information on user-defined operators
- 162. User-Defined Operators 4-10 Oracle Database SQL Reference
- 163. Functions 5-1 5 Functions Functions are similar to operators in that they manipulate data items and return a result. Functions differ from operators in the format of their arguments. This format enables them to operate on zero, one, two, or more arguments: function(argument, argument, ...) A function without any arguments is similar to a pseudocolumn (please refer to Chapter 3, "Pseudocolumns"). However, a pseudocolumn typically returns a different value for each row in the result set, whereas a function without any arguments typically returns the same value for each row. This chapter contains these sections: ■ SQL Functions ■ User-Defined Functions SQL Functions SQL functions are built into Oracle Database and are available for use in various appropriate SQL statements. Do not confuse SQL functions with user-defined functions written in PL/SQL. If you call a SQL function with an argument of a datatype other than the datatype expected by the SQL function, then Oracle attempts to convert the argument to the expected datatype before performing the SQL function. If you call a SQL function with a null argument, then the SQL function automatically returns null. The only SQL functions that do not necessarily follow this behavior are CONCAT, NVL, REPLACE, and REGEXP_REPLACE. In the syntax diagrams for SQL functions, arguments are indicated by their datatypes. When the parameter function appears in SQL syntax, replace it with one of the Note: The combined values of the NLS_COMP and NLS_SORT settings determine the rules by which characters are sorted and compared. If NLS_COMP is set to LINGUISTIC for your database, then all entities in this chapter will be interpreted according to the rules specified by the NLS_SORT parameter. If NLS_COMP is not set to LINGUISTIC, then the functions are interpreted without regard to the NLS_SORT setting. NLS_SORT can be explicitly set. If it is not set explicitly, it is derived from NLS_LANGUAGE. Please refer to Oracle Database Globalization Support Guide for more information on these settings.
- 164. SQL Functions 5-2 Oracle Database SQL Reference functions described in this section. Functions are grouped by the datatypes of their arguments and their return values. The syntax showing the categories of functions follows: function::= single_row_function::= The sections that follow list the built-in SQL functions in each of the groups illustrated in the preceding diagrams except user-defined functions. All of the built-in SQL functions are then described in alphabetical order. Note: When you apply SQL functions to LOB columns, Oracle Database creates temporary LOBs during SQL and PL/SQL processing. You should ensure that temporary tablespace quota is sufficient for storing these temporary LOBs for your application. See Also: ■ "User-Defined Functions" on page 5-236 for information on user functions and "Data Conversion" on page 2-40 for implicit conversion of datatypes ■ Oracle Text Reference for information on functions used with Oracle Text ■ Oracle Data Mining Application Developer's Guide for information on frequent itemset functions used with Oracle Data Mining See Also: "User-Defined Functions" on page 5-236 and CREATE FUNCTION on page 14-48 single_row_function aggregate_function analytic_function object_reference_function model_function user_defined_function numeric_function character_function data_mining_function datetime_function conversion_function collection_function XML_function miscellaneous_single_row_function
- 165. SQL Functions Functions 5-3 Single-Row Functions Single-row functions return a single result row for every row of a queried table or view. These functions can appear in select lists, WHERE clauses, START WITH and CONNECT BY clauses, and HAVING clauses. Numeric Functions Numeric functions accept numeric input and return numeric values. Most numeric functions that return NUMBER values that are accurate to 38 decimal digits. The transcendental functions COS, COSH, EXP, LN, LOG, SIN, SINH, SQRT, TAN, and TANH are accurate to 36 decimal digits. The transcendental functions ACOS, ASIN, ATAN, and ATAN2 are accurate to 30 decimal digits. The numeric functions are: ABS ACOS ASIN ATAN ATAN2 BITAND CEIL COS COSH EXP FLOOR LN LOG MOD NANVL POWER REMAINDER ROUND (number) SIGN SIN SINH SQRT TAN TANH TRUNC (number) WIDTH_BUCKET Character Functions Returning Character Values Character functions that return character values return values of the following datatypes unless otherwise documented: ■ If the input argument is CHAR or VARCHAR2, then the value returned is VARCHAR2. ■ If the input argument is NCHAR or NVARCHAR2, then the value returned is NVARCHAR2. The length of the value returned by the function is limited by the maximum length of the datatype returned. ■ For functions that return CHAR or VARCHAR2, if the length of the return value exceeds the limit, then Oracle Database truncates it and returns the result without an error message. ■ For functions that return CLOB values, if the length of the return values exceeds the limit, then Oracle raises an error and returns no data.
- 166. SQL Functions 5-4 Oracle Database SQL Reference The character functions that return character values are: CHR CONCAT INITCAP LOWER LPAD LTRIM NLS_INITCAP NLS_LOWER NLSSORT NLS_UPPER REGEXP_REPLACE REGEXP_SUBSTR REPLACE RPAD RTRIM SOUNDEX SUBSTR TRANSLATE TREAT TRIM UPPER NLS Character Functions The NLS character functions return information about the character set. The NLS character functions are: NLS_CHARSET_DECL_LEN NLS_CHARSET_ID NLS_CHARSET_NAME Character Functions Returning Number Values Character functions that return number values can take as their argument any character datatype. The character functions that return number values are: ASCII INSTR LENGTH REGEXP_INSTR Datetime Functions Datetime functions operate on date (DATE), timestamp (TIMESTAMP, TIMESTAMP WITH TIME ZONE, and TIMESTAMP WITH LOCAL TIME ZONE), and interval (INTERVAL DAY TO SECOND, INTERVAL YEAR TO MONTH) values. Some of the datetime functions were designed for the Oracle DATE datatype (ADD_ MONTHS, CURRENT_DATE, LAST_DAY, NEW_TIME, and NEXT_DAY). If you provide a timestamp value as their argument, Oracle Database internally converts the input type to a DATE value and returns a DATE value. The exceptions are the MONTHS_BETWEEN function, which returns a number, and the ROUND and TRUNC functions, which do not accept timestamp or interval values at all. The remaining datetime functions were designed to accept any of the three types of data (date, timestamp, and interval) and to return a value of one of these types.
- 167. SQL Functions Functions 5-5 The datetime functions are: ADD_MONTHS CURRENT_DATE CURRENT_TIMESTAMP DBTIMEZONE EXTRACT (datetime) FROM_TZ LAST_DAY LOCALTIMESTAMP MONTHS_BETWEEN NEW_TIME NEXT_DAY NUMTODSINTERVAL NUMTOYMINTERVAL ROUND (date) SESSIONTIMEZONE SYS_EXTRACT_UTC SYSDATE SYSTIMESTAMP TO_CHAR (datetime) TO_TIMESTAMP TO_TIMESTAMP_TZ TO_DSINTERVAL TO_YMINTERVAL TRUNC (date) TZ_OFFSET General Comparison Functions The general comparison functions determine the greatest and or least value from a set of values. The general comparison functions are: GREATEST LEAST Conversion Functions Conversion functions convert a value from one datatype to another. Generally, the form of the function names follows the convention datatype TO datatype. The first datatype is the input datatype. The second datatype is the output datatype. The SQL conversion functions are: ASCIISTR BIN_TO_NUM CAST CHARTOROWID COMPOSE CONVERT DECOMPOSE HEXTORAW NUMTODSINTERVAL NUMTOYMINTERVAL RAWTOHEX RAWTONHEX ROWIDTOCHAR ROWIDTONCHAR SCN_TO_TIMESTAMP
- 168. SQL Functions 5-6 Oracle Database SQL Reference TIMESTAMP_TO_SCN TO_BINARY_DOUBLE TO_BINARY_FLOAT TO_CHAR (character) TO_CHAR (datetime) TO_CHAR (number) TO_CLOB TO_DATE TO_DSINTERVAL TO_LOB TO_MULTI_BYTE TO_NCHAR (character) TO_NCHAR (datetime) TO_NCHAR (number) TO_NCLOB TO_NUMBER TO_DSINTERVAL TO_SINGLE_BYTE TO_TIMESTAMP TO_TIMESTAMP_TZ TO_YMINTERVAL TO_YMINTERVAL TRANSLATE ... USING UNISTR Large Object Functions The large object functions operate on LOBs. The large object functions are: BFILENAME EMPTY_BLOB, EMPTY_CLOB Collection Functions The collection functions operate on nested tables and varrays. The SQL collection functions are: CARDINALITY COLLECT POWERMULTISET POWERMULTISET_BY_CARDINALITY SET Hierarchical Function The hierarchical function applies hierarchical path information to a result set. SYS_CONNECT_BY_PATH Data Mining Functions The data mining functions operate on models that have been built using the DBMS_ DATA_MINING package or the Oracle Data Mining Java API. The SQL data mining functions are: CLUSTER_ID CLUSTER_PROBABILITY CLUSTER_SET FEATURE_ID
- 169. SQL Functions Functions 5-7 FEATURE_SET FEATURE_VALUE PREDICTION PREDICTION_COST PREDICTION_DETAILS PREDICTION_PROBABILITY PREDICTION_SET XML Functions The XML functions operate on or return XML documents or fragments. For more information about selecting and querying XML data using these functions, including information on formatting output, please refer to Oracle XML DB Developer's Guide. The SQL XML functions are: APPENDCHILDXML DELETEXML DEPTH EXTRACT (XML) EXISTSNODE EXTRACTVALUE INSERTCHILDXML INSERTXMLBEFORE PATH SYS_DBURIGEN SYS_XMLAGG SYS_XMLGEN UPDATEXML XMLAGG XMLCDATA XMLCOLATTVAL XMLCOMMENT XMLCONCAT XMLFOREST XMLPARSE XMLPI XMLQUERY XMLROOT XMLSEQUENCE XMLSERIALIZE XMLTABLE XMLTRANSFORM Encoding and Decoding Functions The encoding and decoding functions let you inspect and decode data in the database. DECODE DUMP ORA_HASH VSIZE NULL-Related Functions The NULL-related functions facilitate null handling. The NULL-related functions are: COALESCE LNNVL
- 170. SQL Functions 5-8 Oracle Database SQL Reference NULLIF NVL NVL2 Environment and Identifier Functions The environment and identifier functions provide information about the instance and session. These functions are: SYS_CONTEXT SYS_GUID SYS_TYPEID UID USER USERENV Aggregate Functions Aggregate functions return a single result row based on groups of rows, rather than on single rows. Aggregate functions can appear in select lists and in ORDER BY and HAVING clauses. They are commonly used with the GROUP BY clause in a SELECT statement, where Oracle Database divides the rows of a queried table or view into groups. In a query containing a GROUP BY clause, the elements of the select list can be aggregate functions, GROUP BY expressions, constants, or expressions involving one of these. Oracle applies the aggregate functions to each group of rows and returns a single result row for each group. If you omit the GROUP BY clause, then Oracle applies aggregate functions in the select list to all the rows in the queried table or view. You use aggregate functions in the HAVING clause to eliminate groups from the output based on the results of the aggregate functions, rather than on the values of the individual rows of the queried table or view. Many (but not all) aggregate functions that take a single argument accept these clauses: ■ DISTINCT causes an aggregate function to consider only distinct values of the argument expression. ■ ALL causes an aggregate function to consider all values, including all duplicates. For example, the DISTINCT average of 1, 1, 1, and 3 is 2. The ALL average is 1.5. If you specify neither, then the default is ALL. All aggregate functions except COUNT(*) and GROUPING ignore nulls. You can use the NVL function in the argument to an aggregate function to substitute a value for a null. COUNT never returns null, but returns either a number or zero. For all the remaining aggregate functions, if the data set contains no rows, or contains only rows with nulls as arguments to the aggregate function, then the function returns null. The aggregate functions MIN, MAX, SUM, AVG, COUNT, VARIANCE, and STDDEV, when followed by the KEEP keyword, can be used in conjunction with the FIRST or LAST function to operate on a set of values from a set of rows that rank as the FIRST or LAST with respect to a given sorting specification. Please refer to FIRST on page 5-68 for more information. See Also: "Using the GROUP BY Clause: Examples" on page 19-32 and the "HAVING Clause" on page 19-23 for more information on the GROUP BY clause and HAVING clauses in queries and subqueries
- 171. SQL Functions Functions 5-9 You can nest aggregate functions. For example, the following example calculates the average of the maximum salaries of all the departments in the sample schema hr: SELECT AVG(MAX(salary)) FROM employees GROUP BY department_id; AVG(MAX(SALARY)) ---------------- 10925 This calculation evaluates the inner aggregate (MAX(salary)) for each group defined by the GROUP BY clause (department_id), and aggregates the results again. The aggregate functions are: AVG COLLECT CORR CORR_* COUNT COVAR_POP COVAR_SAMP CUME_DIST DENSE_RANK FIRST GROUP_ID GROUPING GROUPING_ID LAST MAX MEDIAN MIN PERCENTILE_CONT PERCENTILE_DISC PERCENT_RANK RANK REGR_ (Linear Regression) Functions STATS_BINOMIAL_TEST STATS_CROSSTAB STATS_F_TEST STATS_KS_TEST STATS_MODE STATS_MW_TEST STATS_ONE_WAY_ANOVA STATS_T_TEST_* STATS_WSR_TEST STDDEV STDDEV_POP STDDEV_SAMP SUM VAR_POP VAR_SAMP VARIANCE Analytic Functions Analytic functions compute an aggregate value based on a group of rows. They differ from aggregate functions in that they return multiple rows for each group. The group
- 172. SQL Functions 5-10 Oracle Database SQL Reference of rows is called a window and is defined by the analytic_clause. For each row, a sliding window of rows is defined. The window determines the range of rows used to perform the calculations for the current row. Window sizes can be based on either a physical number of rows or a logical interval such as time. Analytic functions are the last set of operations performed in a query except for the final ORDER BY clause. All joins and all WHERE, GROUP BY, and HAVING clauses are completed before the analytic functions are processed. Therefore, analytic functions can appear only in the select list or ORDER BY clause. Analytic functions are commonly used to compute cumulative, moving, centered, and reporting aggregates. analytic_function::= analytic_clause::= query_partition_clause::= order_by_clause::= windowing_clause::= analytic_function ( arguments ) OVER ( analytic_clause ) query_partition_clause order_by_clause windowing_clause PARTITION BY expr , ( expr , ) ORDER SIBLINGS BY expr position c_alias ASC DESC NULLS FIRST NULLS LAST , ROWS RANGE BETWEEN UNBOUNDED PRECEDING CURRENT ROW value_expr PRECEDING FOLLOWING AND UNBOUNDED FOLLOWING CURRENT ROW value_expr PRECEDING FOLLOWING UNBOUNDED PRECEDING CURRENT ROW value_expr PRECEDING
- 173. SQL Functions Functions 5-11 The semantics of this syntax are discussed in the sections that follow. analytic_function Specify the name of an analytic function (see the listing of analytic functions following this discussion of semantics). arguments Analytic functions take 0 to 3 arguments. The arguments can be any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. Oracle determines the argument with the highest numeric precedence and implicitly converts the remaining arguments to that datatype. The return type is also that datatype, unless otherwise noted for an individual function. analytic_clause Use OVER analytic_clause to indicate that the function operates on a query result set. That is, it is computed after the FROM, WHERE, GROUP BY, and HAVING clauses. You can specify analytic functions with this clause in the select list or ORDER BY clause. To filter the results of a query based on an analytic function, nest these functions within the parent query, and then filter the results of the nested subquery. Notes on the analytic_clause: The following notes apply to the analytic_clause: ■ You cannot specify any analytic function in any part of the analytic_clause. That is, you cannot nest analytic functions. However, you can specify an analytic function in a subquery and compute another analytic function over it. ■ You can specify OVER analytic_clause with user-defined analytic functions as well as built-in analytic functions. See CREATE FUNCTION on page 14-48. query_partition_clause Use the PARTITION BY clause to partition the query result set into groups based on one or more value_expr. If you omit this clause, then the function treats all rows of the query result set as a single group. To use the query_partition_clause in an analytic function, use the upper branch of the syntax (without parentheses). To use this clause in a model query (in the model_column_clauses) or a partitioned outer join (in the outer_join_clause), use the lower branch of the syntax (with parentheses). You can specify multiple analytic functions in the same query, each with the same or different PARTITION BY keys. If the objects being queried have the parallel attribute, and if you specify an analytic function with the query_partition_clause, then the function computations are parallelized as well. Valid values of value_expr are constants, columns, nonanalytic functions, function expressions, or expressions involving any of these. order_by_clause Use the order_by_clause to specify how data is ordered within a partition. For all analytic functions except PERCENTILE_CONT and PERCENTILE_DISC (which take See Also: "Numeric Precedence" on page 2-13 for information on numeric precedence and Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion
- 174. SQL Functions 5-12 Oracle Database SQL Reference only a single key), you can order the values in a partition on multiple keys, each defined by a value_expr and each qualified by an ordering sequence. Within each function, you can specify multiple ordering expressions. Doing so is especially useful when using functions that rank values, because the second expression can resolve ties between identical values for the first expression. Whenever the order_by_clause results in identical values for multiple rows, the function returns the same result for each of those rows. Please refer to the analytic example for SUM on page 5-174 for an illustration of this behavior. Restrictions on the ORDER BY Clause The following restrictions apply to the ORDER BY clause: ■ When used in an analytic function, the order_by_clause must take an expression (expr). The SIBLINGS keyword is not valid (it is relevant only in hierarchical queries). Position (position) and column aliases (c_alias) are also invalid. Otherwise this order_by_clause is the same as that used to order the overall query or subquery. ■ An analytic function that uses the RANGE keyword can use multiple sort keys in its ORDER BY clause if it specifies either of these two windows: – RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW. The short form of this is RANGE UNBOUNDED PRECEDING. – RANGE BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING. The short form of this is RANGE UNBOUNDED FOLLOWING. Window boundaries other than these two can have only one sort key in the ORDER BY clause of the analytic function. This restriction does not apply to window boundaries specified by the ROW keyword. ASC | DESC Specify the ordering sequence (ascending or descending). ASC is the default. NULLS FIRST | NULLS LAST Specify whether returned rows containing nulls should appear first or last in the ordering sequence. NULLS LAST is the default for ascending order, and NULLS FIRST is the default for descending order. Analytic functions always operate on rows in the order specified in the order_by_ clause of the function. However, the order_by_clause of the function does not guarantee the order of the result. Use the order_by_clause of the query to guarantee the final result ordering. windowing_clause Some analytic functions allow the windowing_clause. In the listing of analytic functions at the end of this section, the functions that allow the windowing_clause are followed by an asterisk (*). ROWS | RANGE These keywords define for each row a window (a physical or logical set of rows) used for calculating the function result. The function is then applied to all the rows in the window. The window moves through the query result set or partition from top to bottom. See Also: order_by_clause of SELECT on page 19-28 for more information on this clause
- 175. SQL Functions Functions 5-13 ■ ROWS specifies the window in physical units (rows). ■ RANGE specifies the window as a logical offset. You cannot specify this clause unless you have specified the order_by_clause. Some window boundaries defined by the RANGE clause let you specify only one expression in the order_by_clause. Please refer to "Restrictions on the ORDER BY Clause" on page 5-12. The value returned by an analytic function with a logical offset is always deterministic. However, the value returned by an analytic function with a physical offset may produce nondeterministic results unless the ordering expression results in a unique ordering. You may have to specify multiple columns in the order_by_clause to achieve this unique ordering. BETWEEN ... AND Use the BETWEEN ... AND clause to specify a start point and end point for the window. The first expression (before AND) defines the start point and the second expression (after AND) defines the end point. If you omit BETWEEN and specify only one end point, then Oracle considers it the start point, and the end point defaults to the current row. UNBOUNDED PRECEDING Specify UNBOUNDED PRECEDING to indicate that the window starts at the first row of the partition. This is the start point specification and cannot be used as an end point specification. UNBOUNDED FOLLOWING Specify UNBOUNDED FOLLOWING to indicate that the window ends at the last row of the partition. This is the end point specification and cannot be used as a start point specification. CURRENT ROW As a start point, CURRENT ROW specifies that the window begins at the current row or value (depending on whether you have specified ROW or RANGE, respectively). In this case the end point cannot be value_expr PRECEDING. As an end point, CURRENT ROW specifies that the window ends at the current row or value (depending on whether you have specified ROW or RANGE, respectively). In this case the start point cannot be value_expr FOLLOWING. value_expr PRECEDING or value_expr FOLLOWING For RANGE or ROW: ■ If value_expr FOLLOWING is the start point, then the end point must be value_ expr FOLLOWING. ■ If value_expr PRECEDING is the end point, then the start point must be value_ expr PRECEDING. If you are defining a logical window defined by an interval of time in numeric format, then you may need to use conversion functions. If you specified ROWS: ■ value_expr is a physical offset. It must be a constant or expression and must evaluate to a positive numeric value. ■ If value_expr is part of the start point, then it must evaluate to a row before the end point. See Also: NUMTOYMINTERVAL on page 5-109 and NUMTODSINTERVAL on page 5-108 for information on converting numeric times into intervals
- 176. SQL Functions 5-14 Oracle Database SQL Reference If you specified RANGE: ■ value_expr is a logical offset. It must be a constant or expression that evaluates to a positive numeric value or an interval literal. Please refer to "Literals" on page 2-44 for information on interval literals. ■ You can specify only one expression in the order_by_clause ■ If value_expr evaluates to a numeric value, then the ORDER BY expr must be a numeric or DATE datatype. ■ If value_expr evaluates to an interval value, then the ORDER BY expr must be a DATE datatype. If you omit the windowing_clause entirely, then the default is RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW. Analytic functions are commonly used in data warehousing environments. In the list of analytic functions that follows, functions followed by an asterisk (*) allow the full syntax, including the windowing_clause. AVG * CORR * COVAR_POP * COVAR_SAMP * COUNT * CUME_DIST DENSE_RANK FIRST FIRST_VALUE * LAG LAST LAST_VALUE * LEAD MAX * MIN * NTILE PERCENT_RANK PERCENTILE_CONT PERCENTILE_DISC RANK RATIO_TO_REPORT REGR_ (Linear Regression) Functions * ROW_NUMBER STDDEV * STDDEV_POP * STDDEV_SAMP * SUM * VAR_POP * VAR_SAMP * VARIANCE * Object Reference Functions Object reference functions manipulate REF values, which are references to objects of specified object types. The object reference functions are: See Also: Oracle Database Data Warehousing Guide for more information on these functions and for scenarios illustrating their use
- 177. ABS Functions 5-15 DEREF MAKE_REF REF REFTOHEX VALUE Model Functions Model functions can be used only in the model_clause of the SELECT statement. The model functions are: CV ITERATION_NUMBER PRESENTNNV PRESENTV PREVIOUS Alphabetical Listing of SQL Functions The SQL functions are described in alphabetical order. ABS Syntax Purpose ABS returns the absolute value of n. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument. Examples The following example returns the absolute value of -15: SELECT ABS(-15) "Absolute" FROM DUAL; Absolute ---------- 15 See Also: Oracle Database Concepts for more information about REF datatypes See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion ABS ( n )
- 178. ACOS 5-16 Oracle Database SQL Reference ACOS Syntax Purpose ACOS returns the arc cosine of n. The argument n must be in the range of -1 to 1, and the function returns a value in the range of 0 to pi, expressed in radians. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. If the argument is BINARY_ FLOAT, then the function returns BINARY_DOUBLE. Otherwise the function returns the same numeric datatype as the argument. Examples The following example returns the arc cosine of .3: SELECT ACOS(.3)"Arc_Cosine" FROM DUAL; Arc_Cosine ---------- 1.26610367 ADD_MONTHS Syntax Purpose ADD_MONTHS returns the date date plus integer months. The date argument can be a datetime value or any value that can be implicitly converted to DATE. The integer argument can be an integer or any value that can be implicitly converted to an integer. The return type is always DATE, regardless of the datatype of date. If date is the last day of the month or if the resulting month has fewer days than the day component of date, then the result is the last day of the resulting month. Otherwise, the result has the same day component as date. Examples The following example returns the month after the hire_date in the sample table employees: SELECT TO_CHAR( ADD_MONTHS(hire_date,1), 'DD-MON-YYYY') "Next month" FROM employees WHERE last_name = 'Baer'; See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion ACOS ( n ) ADD_MONTHS ( date , integer )
- 179. APPENDCHILDXML Functions 5-17 Next Month ----------- 07-JUL-1994 APPENDCHILDXML Syntax Purpose APPENDCHILDXML appends a user-supplied value onto the target XML as the child of the node indicated by an XPath expression. ■ XMLType_instance is an instance of XMLType. ■ The XPath_string is an Xpath expression indicating one or more nodes onto which one or more child nodes are to be appended. You can specify an absolute XPath_string with an initial slash or a relative XPath_string by omitting the initial slash. If you omit the initial slash, the context of the relative path defaults to the root node. ■ The value_expr specifies one or more nodes of XMLType. It must resolve to a string. ■ The optional namespace_string provides namespace information for the XPath_string. This parameter must be of type VARCHAR2. Examples The following example adds an /Owner node to the /Warehouse/Building node of warehouse_spec in the oe.warehouses table if the value of the /Building node is "Rented": UPDATE warehouses SET warehouse_spec = APPENDCHILDXML(warehouse_spec, 'Warehouse/Building', XMLType('<Owner>Grandco</Owner>')) WHERE EXTRACTVALUE(warehouse_spec, '/Warehouse/Building') = 'Rented'; SELECT warehouse_id, warehouse_name, EXTRACTVALUE(warehouse_spec, '/Warehouse/Building/Owner') "Prop.Owner" FROM warehouses WHERE EXISTSNODE(warehouse_spec, '/Warehouse/Building/Owner') = 1; WAREHOUSE_ID WAREHOUSE_NAME Prop.Owner ------------ --------------- ---------- 2 San Francisco Grandco 3 New Jersey Grandco See Also: Oracle XML DB Developer's Guide for more information about this function APPENDCHILDXML ( XMLType_instance , XPath_string , value_expr , namespace_string )
- 180. ASCIISTR 5-18 Oracle Database SQL Reference ASCIISTR Syntax Purpose ASCIISTR takes as its argument a string, or an expression that resolves to a string, in any character set and returns an ASCII version of the string in the database character set. Non-ASCII characters are converted to the form xxxx, where xxxx represents a UTF-16 code unit. Examples The following example returns the ASCII string equivalent of the text string "ABÄCDE": SELECT ASCIISTR('ABÄCDE') FROM DUAL; ASCIISTR(' ---------- AB00C4CDE ASCII Syntax Purpose ASCII returns the decimal representation in the database character set of the first character of char. char can be of datatype CHAR, VARCHAR2, NCHAR, or NVARCHAR2. The value returned is of datatype NUMBER. If your database character set is 7-bit ASCII, then this function returns an ASCII value. If your database character set is EBCDIC Code, then this function returns an EBCDIC value. There is no corresponding EBCDIC character function. This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion. Examples The following example returns employees whose last names begin with the letter L, whose ASCII equivalent is 76: SELECT last_name FROM employees WHERE ASCII(SUBSTR(last_name, 1, 1,)) = 76; LAST_NAME ------------------------- See Also: Oracle Database Globalization Support Guide for information on Unicode character sets and character semantics See Also: "Datatype Comparison Rules" on page 2-37 for more information ASCIISTR ( char ) ASCII ( char )
- 181. ATAN Functions 5-19 Ladwig Landry Lee Livingston ASIN Syntax Purpose ASIN returns the arc sine of n. The argument n must be in the range of -1 to 1, and the function returns a value in the range of -pi/2 to pi/2, expressed in radians. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. If the argument is BINARY_ FLOAT, then the function returns BINARY_DOUBLE. Otherwise the function returns the same numeric datatype as the argument. Examples The following example returns the arc sine of .3: SELECT ASIN(.3) "Arc_Sine" FROM DUAL; Arc_Sine ---------- .304692654 ATAN Syntax Purpose ATAN returns the arc tangent of n. The argument n can be in an unbounded range and returns a value in the range of -pi/2 to pi/2, expressed in radians. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. If the argument is BINARY_ FLOAT, then the function returns BINARY_DOUBLE. Otherwise the function returns the same numeric datatype as the argument. Examples The following example returns the arc tangent of .3: SELECT ATAN(.3) "Arc_Tangent" FROM DUAL; See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion ASIN ( n ) ATAN ( n )
- 182. ATAN2 5-20 Oracle Database SQL Reference Arc_Tangent ---------- .291456794 ATAN2 Syntax Purpose ATAN2 returns the arc tangent of n1 and n2. The argument n1 can be in an unbounded range and returns a value in the range of -pi to pi, depending on the signs of n1 and n2, expressed in radians. ATAN2(n1,n2) is the same as ATAN2(n1/n2). This function takes as arguments any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. If any argument is BINARY_ FLOAT or BINARY_DOUBLE, then the function returns BINARY_DOUBLE. Otherwise the function returns NUMBER. Examples The following example returns the arc tangent of .3 and .2: SELECT ATAN2(.3, .2) "Arc_Tangent2" FROM DUAL; Arc_Tangent2 ------------ .982793723 AVG Syntax Purpose AVG returns average value of expr. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument. See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions ATAN2 ( n1 , / n2 ) AVG ( DISTINCT ALL expr ) OVER ( analytic_clause )
- 183. BFILENAME Functions 5-21 If you specify DISTINCT, then you can specify only the query_partition_clause of the analytic_clause. The order_by_clause and windowing_clause are not allowed. Aggregate Example The following example calculates the average salary of all employees in the hr.employees table: SELECT AVG(salary) "Average" FROM employees; Average -------- 6425 Analytic Example The following example calculates, for each employee in the employees table, the average salary of the employees reporting to the same manager who were hired in the range just before through just after the employee: SELECT manager_id, last_name, hire_date, salary, AVG(salary) OVER (PARTITION BY manager_id ORDER BY hire_date ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS c_mavg FROM employees; MANAGER_ID LAST_NAME HIRE_DATE SALARY C_MAVG ---------- ------------------------- --------- ---------- ---------- 100 Kochhar 21-SEP-89 17000 17000 100 De Haan 13-JAN-93 17000 15000 100 Raphaely 07-DEC-94 11000 11966.6667 100 Kaufling 01-MAY-95 7900 10633.3333 100 Hartstein 17-FEB-96 13000 9633.33333 100 Weiss 18-JUL-96 8000 11666.6667 100 Russell 01-OCT-96 14000 11833.3333 . . . BFILENAME Syntax Purpose BFILENAME returns a BFILE locator that is associated with a physical LOB binary file on the server file system. ■ 'directory' is a database object that serves as an alias for a full path name on the server file system where the files are actually located. ■ 'filename' is the name of the file in the server file system. See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion See Also: "About SQL Expressions" on page 6-1 for information on valid forms of expr and "Aggregate Functions" on page 5-8 BFILENAME ( ’ directory ’ , ’ filename ’ )
- 184. BIN_TO_NUM 5-22 Oracle Database SQL Reference You must create the directory object and associate a BFILE value with a physical file before you can use them as arguments to BFILENAME in a SQL or PL/SQL statement, DBMS_LOB package, or OCI operation. You can use this function in two ways: ■ In a DML statement to initialize a BFILE column ■ In a programmatic interface to access BFILE data by assigning a value to the BFILE locator. The directory argument is case sensitive. That is, you must ensure that you specify the directory object name exactly as it exists in the data dictionary. For example, if an "Admin" directory object was created using mixed case and a quoted identifier in the CREATE DIRECTORY statement, then when using the BFILENAME function you must refer to the directory object as 'Admin'. You must specify the filename argument according to the case and punctuation conventions for your operating system. Examples The following example inserts a row into the sample table pm.print_media. The example uses the BFILENAME function to identify a binary file on the server file system in the directory $ORACLE_HOME/demo/schema/product_media. The example shows how the directory database object media_dir was created in the PM schema. CREATE DIRECTORY media_dir AS '/demo/schema/product_media'; INSERT INTO print_media (product_id, ad_id, ad_graphic) VALUES (3000, 31001, BFILENAME('MEDIA_DIR', 'modem_comp_ad.gif')); BIN_TO_NUM Syntax Purpose BIN_TO_NUM converts a bit vector to its equivalent number. Each argument to this function represents a bit in the bit vector. This function takes as arguments any numeric datatype, or any nonnumeric datatype that can be implicitly converted to NUMBER. Each expr must evaluate to 0 or 1. This function returns Oracle NUMBER. BIN_TO_NUM is useful in data warehousing applications for selecting groups of interest from a materialized view using grouping sets. See Also: ■ Oracle Database Application Developer's Guide - Large Objects and Oracle Call Interface Programmer's Guide for more information on LOBs and for examples of retrieving BFILE data ■ CREATE DIRECTORY on page 14-42 BIN_TO_NUM ( expr , )
- 185. BITAND Functions 5-23 Examples The following example converts a binary value to a number: SELECT BIN_TO_NUM(1,0,1,0) FROM DUAL; BIN_TO_NUM(1,0,1,0) ------------------- 10 BITAND Syntax Purpose BITAND computes an AND operation on the bits of expr1 and expr2, both of which must resolve to nonnegative integers, and returns an integer. This function is commonly used with the DECODE function, as illustrated in the example that follows. An AND operation compares two bit values. If the values are the same, the operator returns 1. If the values are different, the operator returns 0. Only significant bits are compared. For example, an AND operation on the integers 5 (binary 101) and 1 (binary 001 or 1) compares only the rightmost bit, and results in a value of 1 (binary 1). Both arguments can be any numeric datatype, or any nonnumeric datatype that can be implicitly converted to NUMBER. The function returns NUMBER. Examples The following represents each order_status in the sample table oe.orders by individual bits. (The example specifies options that can total only 7, so rows with order_status greater than 7 are eliminated.) SELECT order_id, customer_id, DECODE(BITAND(order_status, 1), 1, 'Warehouse', 'PostOffice') Location, DECODE(BITAND(order_status, 2), 2, 'Ground', 'Air') Method, See Also: ■ group_by_clause on page 19-21 for information on GROUPING SETS syntax ■ Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion ■ Oracle Database Data Warehousing Guide for information on data aggregation in general Note: This function does not determine the datatype of the value returned. Therefore, in SQL*Plus, you must specify BITAND in a wrapper, such as TO_NUMBER, which returns a datatype. See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion BITAND ( expr1 , expr2 )
- 186. CARDINALITY 5-24 Oracle Database SQL Reference DECODE(BITAND(order_status, 4), 4, 'Insured', 'Certified') Receipt FROM orders WHERE order_status < 8; ORDER_ID CUSTOMER_ID LOCATION METHOD RECEIPT ---------- ----------- ---------- ------ --------- 2458 101 PostOffice Air Certified 2397 102 Warehouse Air Certified 2454 103 Warehouse Air Certified 2354 104 PostOffice Air Certified 2358 105 PostOffice Ground Certified 2381 106 Warehouse Ground Certified 2440 107 Warehouse Ground Certified 2357 108 Warehouse Air Insured 2394 109 Warehouse Air Insured 2435 144 PostOffice Ground Insured 2455 145 Warehouse Ground Insured 2356 105 Warehouse Air Insured 2360 107 PostOffice Air Insured ... CARDINALITY Syntax Purpose CARDINALITY returns the number of elements in a nested table. The return type is NUMBER. If the nested table is empty, or is a null collection, then CARDINALITY returns NULL. Examples The following example shows the number of elements in the nested table column ad_ textdocs_ntab of the sample table pm.print_media: SELECT product_id, CARDINALITY(ad_textdocs_ntab) FROM print_media; PRODUCT_ID CARDINALITY(AD_TEXTDOCS_NTAB) ---------- ----------------------------- 3060 3 2056 3 3106 3 2268 3 CAST Syntax CARDINALITY ( nested_table ) CAST ( expr MULTISET ( subquery ) AS type_name )
- 187. CAST Functions 5-25 Purpose CAST converts one built-in datatype or collection-typed value into another built-in datatype or collection-typed value. CAST lets you convert built-in datatypes or collection-typed values of one type into another built-in datatype or collection type. You can cast an unnamed operand (such as a date or the result set of a subquery) or a named collection (such as a varray or a nested table) into a type-compatible datatype or named collection. The type_name must be the name of a built-in datatype or collection type and the operand must be a built-in datatype or must evaluate to a collection value. For the operand, expr can be either a built-in datatype, a collection type, or an instance of an ANYDATA type. If expr is an instance of an ANYDATA type, CAST will try to extract the value of the ANYDATA instance and return it if it matches the cast target type, otherwise, null will be returned. MULTISET informs Oracle Database to take the result set of the subquery and return a collection value. Table 5–1 shows which built-in datatypes can be cast into which other built-in datatypes. (CAST does not support LONG, LONG RAW, or the Oracle-supplied types.) CAST does not directly support any of the LOB datatypes. When you use CAST to convert a CLOB value into a character datatype or a BLOB value into the RAW datatype, the database implicitly converts the LOB value to character or raw data and then explicitly casts the resulting value into the target datatype. If the resulting value is larger than the target type, then the database returns an error. When you use CAST ... MULTISET to get a collection value, each select list item in the query passed to the CAST function is converted to the corresponding attribute type of the target collection element type. Note 1: Datetime/interval includes DATE, TIMESTAMP, TIMESTAMP WITH TIMEZONE, INTERVAL DAY TO SECOND, and INTERVAL YEAR TO MONTH. Note 2: You cannot cast a UROWID to a ROWID if the UROWID contains the value of a ROWID of an index-organized table. If you want to cast a named collection type into another named collection type, then the elements of both collections must be of the same type. Table 5–1 Casting Built-In Datatypes from BINARY_ FLOAT, BINARY_ DOUBLE from CHAR, VARCHAR2 from NUMBER from DATETIME / INTERVAL (Note 1) from RAW from ROWID, UROWID (Note 2) from NCHAR, NVARCHAR2 to BINARY_FLOAT, BINARY_DOUBLE X X X -- -- -- X to CHAR, VARCHAR2 X X X X X X -- to NUMBER X X X -- -- -- X to DATE, TIMESTAMP, INTERVAL -- X -- X -- -- -- to RAW -- X -- -- X -- -- to ROWID, UROWID -- X -- -- -- Xa -- to NCHAR, NVARCHAR2 X -- X X X X X
- 188. CAST 5-26 Oracle Database SQL Reference If the result set of subquery can evaluate to multiple rows, then you must specify the MULTISET keyword. The rows resulting from the subquery form the elements of the collection value into which they are cast. Without the MULTISET keyword, the subquery is treated as a scalar subquery. Built-In Datatype Examples The following examples use the CAST function with scalar datatypes: SELECT CAST('22-OCT-1997' AS TIMESTAMP WITH LOCAL TIME ZONE) FROM dual; SELECT product_id, CAST(ad_sourcetext AS VARCHAR2(30)) FROM print_media; Collection Examples The CAST examples that follow build on the cust_address_typ found in the sample order entry schema, oe. CREATE TYPE address_book_t AS TABLE OF cust_address_typ; / CREATE TYPE address_array_t AS VARRAY(3) OF cust_address_typ; / CREATE TABLE cust_address ( custno NUMBER, street_address VARCHAR2(40), postal_code VARCHAR2(10), city VARCHAR2(30), state_province VARCHAR2(10), country_id CHAR(2)); CREATE TABLE cust_short (custno NUMBER, name VARCHAR2(31)); CREATE TABLE states (state_id NUMBER, addresses address_array_t); This example casts a subquery: SELECT s.custno, s.name, CAST(MULTISET(SELECT ca.street_address, ca.postal_code, ca.city, ca.state_province, ca.country_id FROM cust_address ca WHERE s.custno = ca.custno) AS address_book_t) FROM cust_short s; CAST converts a varray type column into a nested table: SELECT CAST(s.addresses AS address_book_t) FROM states s WHERE s.state_id = 111; The following objects create the basis of the example that follows: See Also: "Implicit Data Conversion" on page 2-41 for information on how Oracle Database implicitly converts collection type data into character data
- 189. CHARTOROWID Functions 5-27 CREATE TABLE projects (employee_id NUMBER, project_name VARCHAR2(10)); CREATE TABLE emps_short (employee_id NUMBER, last_name VARCHAR2(10)); CREATE TYPE project_table_typ AS TABLE OF VARCHAR2(10); / The following example of a MULTISET expression uses these objects: SELECT e.last_name, CAST(MULTISET(SELECT p.project_name FROM projects p WHERE p.employee_id = e.employee_id ORDER BY p.project_name) AS project_table_typ) FROM emps_short e; CEIL Syntax Purpose CEIL returns smallest integer greater than or equal to n. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument. Examples The following example returns the smallest integer greater than or equal to the order total of a specified order: SELECT order_total, CEIL(order_total) FROM orders WHERE order_id = 2434; ORDER_TOTAL CEIL(ORDER_TOTAL) ----------- ----------------- 268651.8 268652 CHARTOROWID Syntax Purpose CHARTOROWID converts a value from CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype to ROWID datatype. See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion CEIL ( n ) CHARTOROWID ( char )
- 190. CHR 5-28 Oracle Database SQL Reference This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion. Examples The following example converts a character rowid representation to a rowid. (The actual rowid is different for each database instance.) SELECT last_name FROM employees WHERE ROWID = CHARTOROWID('AAAFd1AAFAAAABSAA/'); LAST_NAME ------------------------- Greene CHR Syntax Purpose CHR returns the character having the binary equivalent to n as a VARCHAR2 value in either the database character set or, if you specify USING NCHAR_CS, the national character set. For single-byte character sets, if n > 256, then Oracle Database returns the binary equivalent of n mod 256. For multibyte character sets, n must resolve to one entire code point. Invalid code points are not validated, and the result of specifying invalid code points is indeterminate. This function takes as an argument a NUMBER value, or any value that can be implicitly converted to NUMBER, and returns a character. Examples The following example is run on an ASCII-based machine with the database character set defined as WE8ISO8859P1: SELECT CHR(67)||CHR(65)||CHR(84) "Dog" FROM DUAL; Dog --- CAT See Also: "Datatype Comparison Rules" on page 2-37 for more information. Note: Use of the CHR function (either with or without the optional USING NCHAR_CS clause) results in code that is not portable between ASCII- and EBCDIC-based machine architectures. See Also: NCHR on page 5-99 and Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion CHR ( n USING NCHAR_CS )
- 191. CLUSTER_ID Functions 5-29 To produce the same results on an EBCDIC-based machine with the WE8EBCDIC1047 character set, the preceding example would have to be modified as follows: SELECT CHR(195)||CHR(193)||CHR(227) "Dog" FROM DUAL; Dog --- CAT For multibyte character sets, this sort of concatenation gives different results. For example, given a multibyte character whose hexadecimal value is a1a2 (a1 representing the first byte and a2 the second byte), you must specify for n the decimal equivalent of 'a1a2', or 41378. That is, you must specify: SELECT CHR(41378) FROM DUAL; You cannot specify the decimal equivalent of a1 concatenated with the decimal equivalent of a2, as in the following example: SELECT CHR(161)||CHR(162) FROM DUAL; However, you can concatenate whole multibyte code points, as in the following example, which concatenates the multibyte characters whose hexadecimal values are a1a2 and a1a3: SELECT CHR(41378)||CHR(41379) FROM DUAL; The following example assumes that the national character set is UTF16: SELECT CHR (196 USING NCHAR_CS) FROM DUAL; CH -- Ä CLUSTER_ID Syntax mining_attribute_clause::= Purpose This function is for use with clustering models that have been created using the DBMS_ DATA_MINING package or with the Oracle Data Mining Java API. It returns the cluster CLUSTER_ID ( schema . model mining_attribute_clause ) USING * schema . table . * expr AS alias ,
- 192. CLUSTER_PROBABILITY 5-30 Oracle Database SQL Reference identifier of the predicted cluster with the highest probability for the set of predictors specified in the mining_attribute_clause. The value returned is an Oracle NUMBER. The mining_attribute_clause behaves as described for the PREDICTION function. Please refer to mining_attribute_clause on page 5-121. Examples The following example lists the clusters into which customers of a given dataset have been grouped. This example, and the prerequisite data mining operations, including the creation of the dm_sh_clus_sample model and the dm_sh_sample_apply_prepared view, can be found in the demo file $ORACLE_HOME/rdbms/demo/dmkmdemo.sql. General information on data mining demo files is available in Oracle Data Mining Administrator's Guide. The example is presented here to illustrate the syntactic use of the function. SELECT CLUSTER_ID(km_sh_clus_sample USING *) AS clus, COUNT(*) AS cnt FROM km_sh_sample_apply_prepared GROUP BY CLUSTER_ID(km_sh_clus_sample USING *) ORDER BY cnt DESC; CLUS CNT ---------- ---------- 2 580 10 199 6 185 8 115 12 98 16 82 19 81 15 68 18 65 14 27 10 rows selected. CLUSTER_PROBABILITY Syntax See Also: ■ Oracle Data Mining Concepts for detailed information on Oracle Data Mining features ■ Oracle Data Mining Administrator's Guide for information on the demo programs available in the code ■ Oracle Data Mining Application Developer's Guide for information on writing Oracle Data Mining applications ■ PREDICTION on page 5-120 CLUSTER_PROBABILITY ( schema . model , cluster_id mining_attribute_clause )
- 193. CLUSTER_PROBABILITY Functions 5-31 mining_attribute_clause::= Purpose This function is for use with clustering models that have been created with the DBMS_ DATA_MINING package or with the Oracle Data Mining Java API. It returns a measure of the degree of confidence of membership of an input row in a cluster associated with the specified model. ■ For cluster_id, specify the identifier of the cluster in the model. The function returns the probability for the specified cluster. If you omit this clause, then the function returns the probability associated with the best predicted cluster. You can use the form without cluster_id in conjunction with the CLUSTER_ID function to obtain the best predicted pair of cluster ID and probability. ■ The mining_attribute_clause behaves as described for the PREDICTION function. Please refer to mining_attribute_clause on page 5-121 Examples The following example determines the ten most representative customers, based on likelihood, in cluster 2. This example, and the prerequisite data mining operations, including the creation of the dm_sh_clus_sample model and the dm_sh_sample_apply_prepared view, can be found in the demo file $ORACLE_HOME/rdbms/demo/dmkmdemo.sql. General information on data mining demo files is available in Oracle Data Mining Administrator's Guide. The example is presented here to illustrate the syntactic use of the function. SELECT * FROM (SELECT cust_id, CLUSTER_PROBABILITY(km_sh_clus_sample, 2 USING *) prob FROM km_sh_sample_apply_prepared ORDER BY prob DESC) WHERE ROWNUM < 11; CUST_ID PROB ---------- ------ 100052 .9993 See Also: ■ Oracle Data Mining Concepts for detailed information on Oracle Data Mining features ■ Oracle Data Mining Administrator's Guide for information on the demo programs available in the code ■ Oracle Data Mining Application Developer's Guide for information on writing Oracle Data Mining applications ■ CLUSTER_ID on page 5-29 and PREDICTION on page 5-120 for information on related data mining functions USING * schema . table . * expr AS alias ,
- 194. CLUSTER_SET 5-32 Oracle Database SQL Reference 100962 .9993 101208 .9993 100281 .9993 100012 .9993 101009 .9992 100173 .9992 101176 .9991 100672 .9991 101420 .9991 10 rows selected. CLUSTER_SET Syntax mining_attribute_clause::= Purpose This function is for use with clustering models that have been created with the DBMS_ DATA_MINING package or with the Oracle Data Mining Java API. It returns a varray of objects containing all possible clusters that a given row belongs to. Each object in the varray is a pair of scalar values containing the cluster ID and the cluster probability. The object fields are named CLUSTER_ID and PROBABILITY, and both are Oracle NUMBER. ■ For the optional topN argument, specify a positive integer. Doing so restricts the set of predicted clusters to those that have one of the top N probability values. If you omit topN or set it to NULL, then all clusters are returned in the collection. If multiple clusters are tied for the Nth value, the database still returns only N values. ■ For the optional cutoff argument, specify a positive integer to restrict the returned clusters to those with a probability greater than or equal to the specified cutoff. You can filter only by cutoff by specifying NULL for topN and the desired cutoff value for cutoff. You can specify topN and cutoff together to restrict the returned clusters to those that are in the top N and have a probability that passes the threshold. The mining_attribute_clause behaves as described for the PREDICTION function. Please refer to mining_attribute_clause on page 5-121. CLUSTER_SET ( schema . model , topN , cutoff mining_attribute_clause ) USING * schema . table . * expr AS alias ,
- 195. CLUSTER_SET Functions 5-33 Examples The following example lists the most relevant attributes (with confidence > 55%) of each cluster to which customer 101362 belongs with > 20% likelihood. This example, and the prerequisite data mining operations, including the creation of the dm_sh_clus_sample model and the views and type, can be found in the demo file $ORACLE_HOME/rdbms/demo/dmkmdemo.sql. General information on data mining demo files is available in Oracle Data Mining Administrator's Guide. The example is presented here to illustrate the syntactic use of the function. WITH clus_tab AS ( SELECT id, A.attribute_name aname, A.conditional_operator op, NVL(A.attribute_str_value, ROUND(DECODE(A.attribute_name, N.col, A.attribute_num_value * N.scale + N.shift, A.attribute_num_value),4)) val, A.attribute_support support, A.attribute_confidence confidence FROM TABLE(DBMS_DATA_MINING.GET_MODEL_DETAILS_KM('km_sh_clus_sample')) T, TABLE(T.rule.antecedent) A, km_sh_sample_norm N WHERE A.attribute_name = N.col (+) AND A.attribute_confidence > 0.55 ), clust AS ( SELECT id, CAST(COLLECT(Cattr(aname, op, TO_CHAR(val), support, confidence)) AS Cattrs) cl_attrs FROM clus_tab GROUP BY id ), custclus AS ( SELECT T.cust_id, S.cluster_id, S.probability FROM (SELECT cust_id, CLUSTER_SET(km_sh_clus_sample, NULL, 0.2 USING *) pset FROM km_sh_sample_apply_prepared WHERE cust_id = 101362) T, TABLE(T.pset) S ) SELECT A.probability prob, A.cluster_id cl_id, B.attr, B.op, B.val, B.supp, B.conf FROM custclus A, (SELECT T.id, C.* FROM clust T, TABLE(T.cl_attrs) C) B WHERE A.cluster_id = B.id ORDER BY prob DESC, cl_id ASC, conf DESC, attr ASC, val ASC; See Also: ■ Oracle Data Mining Concepts for detailed information on Oracle Data Mining features ■ Oracle Data Mining Administrator's Guide for information on the demo programs available in the code ■ Oracle Data Mining Application Developer's Guide for information on writing Oracle Data Mining applications
- 196. COALESCE 5-34 Oracle Database SQL Reference PROB CL_ID ATTR OP VAL SUPP CONF ------- ---------- --------------- --- --------------- ---------- ------- .7873 8 HOUSEHOLD_SIZE IN 9+ 126 .7500 .7873 8 CUST_MARITAL_ST IN Divorc. 118 .6000 ATUS .7873 8 CUST_MARITAL_ST IN NeverM 118 .6000 ATUS .7873 8 CUST_MARITAL_ST IN Separ. 118 .6000 ATUS .7873 8 CUST_MARITAL_ST IN Widowed 118 .6000 ATUS .2016 6 AGE >= 17 152 .6667 .2016 6 AGE <= 31.6 152 .6667 .2016 6 CUST_MARITAL_ST IN NeverM 168 .6667 ATUS 8 rows selected. COALESCE Syntax Purpose COALESCE returns the first non-null expr in the expression list. At least one expr must not be the literal NULL. If all occurrences of expr evaluate to null, then the function returns null. Oracle Database uses short-circuit evaluation. That is, the database evaluates each expr value and determines whether it is NULL, rather than evaluating all of the expr values before determining whether any of them is NULL. If all occurrences of expr are numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype, then Oracle Database determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype, and returns that datatype. This function is a generalization of the NVL function. You can also use COALESCE as a variety of the CASE expression. For example, COALESCE (expr1, expr2) is equivalent to: CASE WHEN expr1 IS NOT NULL THEN expr1 ELSE expr2 END See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion and "Numeric Precedence" on page 2-13 for information on numeric precedence COALESCE ( expr , )
- 197. COLLECT Functions 5-35 Similarly, COALESCE (expr1, expr2, ..., exprn), for n>=3 is equivalent to: CASE WHEN expr1 IS NOT NULL THEN expr1 ELSE COALESCE (expr2, ..., exprn) END Examples The following example uses the sample oe.product_information table to organize a clearance sale of products. It gives a 10% discount to all products with a list price. If there is no list price, then the sale price is the minimum price. If there is no minimum price, then the sale price is "5": SELECT product_id, list_price, min_price, COALESCE(0.9*list_price, min_price, 5) "Sale" FROM product_information WHERE supplier_id = 102050; PRODUCT_ID LIST_PRICE MIN_PRICE Sale ---------- ---------- ---------- ---------- 2382 850 731 765 3355 5 1770 73 73 2378 305 247 274.5 1769 48 43.2 COLLECT Syntax Purpose COLLECT takes as its argument a column of any type and creates a nested table of the input type out of the rows selected. To get the results of this function you must use it within a CAST function. If column is itself a collection, then the output of COLLECT is a nested table of collections. Examples The following example creates a nested table from the varray column of phone numbers in the sample table oe.customers: CREATE TYPE phone_book_t AS TABLE OF phone_list_typ; / SELECT CAST(COLLECT(phone_numbers) AS phone_book_t) FROM customers; See Also: NVL on page 5-110 and "CASE Expressions" on page 6-5 See Also: CAST on page 5-24 COLLECT ( column )
- 198. COMPOSE 5-36 Oracle Database SQL Reference COMPOSE Syntax Purpose COMPOSE takes as its argument a string, or an expression that resolves to a string, in any datatype, and returns a Unicode string in its fully normalized form in the same character set as the input. char can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. For example, an o code point qualified by an umlaut code point will be returned as the o-umlaut code point. CLOB and NCLOB values are supported through implicit conversion. If char is a character LOB value, it is converted to a VARCHAR value before the COMPOSE operation. The operation will fail if the size of the LOB value exceeds the supported length of the VARCHAR in the particular development environment. Examples The following example returns the o-umlaut code point: SELECT COMPOSE ( 'o' || UNISTR('0308') ) FROM DUAL; CO -- ö CONCAT Syntax Purpose CONCAT returns char1 concatenated with char2. Both char1 and char2 can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The string returned is in the same character set as char1. Its datatype depends on the datatypes of the arguments. In concatenations of two different datatypes, Oracle Database returns the datatype that results in a lossless conversion. Therefore, if one of the arguments is a LOB, then the returned value is a LOB. If one of the arguments is a national datatype, then the returned value is a national datatype. For example: ■ CONCAT(CLOB, NCLOB) returns NCLOB ■ CONCAT(NCLOB, NCHAR) returns NCLOB ■ CONCAT(NCLOB, CHAR) returns NCLOB ■ CONCAT(NCHAR, CLOB) returns NCLOB See Also: Oracle Database Globalization Support Guide for information on Unicode character sets and character semantics See Also: UNISTR on page 5-210 COMPOSE ( char ) CONCAT ( char1 , char2 )
- 199. CONVERT Functions 5-37 This function is equivalent to the concatenation operator (||). Examples This example uses nesting to concatenate three character strings: SELECT CONCAT(CONCAT(last_name, '''s job category is '), job_id) "Job" FROM employees WHERE employee_id = 152; Job ------------------------------------------------------ Hall's job category is SA_REP CONVERT Syntax Purpose CONVERT converts a character string from one character set to another. The datatype of the returned value is VARCHAR2. ■ The char argument is the value to be converted. It can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. ■ The dest_char_set argument is the name of the character set to which char is converted. ■ The source_char_set argument is the name of the character set in which char is stored in the database. The default value is the database character set. Both the destination and source character set arguments can be either literals or columns containing the name of the character set. For complete correspondence in character conversion, it is essential that the destination character set contains a representation of all the characters defined in the source character set. Where a character does not exist in the destination character set, a replacement character appears. Replacement characters can be defined as part of a character set definition. Examples The following example illustrates character set conversion by converting a Latin-1 string to ASCII. The result is the same as importing the same string from a WE8ISO8859P1 database to a US7ASCII database. SELECT CONVERT('Ä Ê Í Õ Ø A B C D E ', 'US7ASCII', 'WE8ISO8859P1') FROM DUAL; CONVERT('ÄÊÍÕØABCDE' --------------------- A E I ? ? A B C D E ? See Also: "Concatenation Operator" on page 4-3 for information on the CONCAT operator CONVERT ( char , dest_char_set , source_char_set )
- 200. CORR 5-38 Oracle Database SQL Reference Common character sets include: ■ US7ASCII: US 7-bit ASCII character set ■ WE8DEC: West European 8-bit character set ■ F7DEC: DEC French 7-bit character set ■ WE8EBCDIC500: IBM West European EBCDIC Code Page 500 ■ WE8ISO8859P1: ISO 8859-1 West European 8-bit character set ■ UTF8: Unicode 4.0 UTF-8 Universal character set, CESU-8 compliant ■ AL32UTF8: Unicode 4.0 UTF-8 Universal character set CORR Syntax Purpose CORR returns the coefficient of correlation of a set of number pairs. You can use it as an aggregate or analytic function. This function takes as arguments any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. Oracle determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype, and returns that datatype. Oracle Database applies the function to the set of (expr1, expr2) after eliminating the pairs for which either expr1 or expr2 is null. Then Oracle makes the following computation: COVAR_POP(expr1, expr2) / (STDDEV_POP(expr1) * STDDEV_POP(expr2)) The function returns a value of type NUMBER. If the function is applied to an empty set, then it returns null. See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion and "Numeric Precedence" on page 2-13 for information on numeric precedence Note: The CORR function calculates the Pearson's correlation coefficient, which requires numeric expressions as arguments. Oracle also provides the CORR_S (Spearman's rho coefficient) and CORR_K (Kendall's tau-b coefficient) to support nonparametric or rank correlation. CORR ( expr1 , expr2 ) OVER ( analytic_clause )
- 201. CORR_* Functions 5-39 Aggregate Example The following example calculates the coefficient of correlation between the list prices and minimum prices of products by weight class in the sample table oe.product_ information: SELECT weight_class, CORR(list_price, min_price) FROM product_information GROUP BY weight_class; WEIGHT_CLASS CORR(LIST_PRICE,MIN_PRICE) ------------ -------------------------- 1 .99914795 2 .999022941 3 .998484472 4 .999359909 5 .999536087 Analytic Example The following example shows the correlation between duration at the company and salary by the employee's position. The result set shows the same correlation for each employee in a given job: SELECT employee_id, job_id, TO_CHAR((SYSDATE - hire_date) YEAR TO MONTH ) "Yrs-Mns", salary, CORR(SYSDATE-hire_date, salary) OVER(PARTITION BY job_id) AS "Correlation" FROM employees WHERE department_id in (50, 80) ORDER BY job_id, employee_id; EMPLOYEE_ID JOB_ID Yrs-Mns SALARY Correlation ----------- ---------- ------- ---------- ----------- 145 SA_MAN +08-07 14000 .912385598 146 SA_MAN +08-04 13500 .912385598 147 SA_MAN +08-02 12000 .912385598 148 SA_MAN +05-07 11000 .912385598 149 SA_MAN +05-03 10500 .912385598 150 SA_REP +08-03 10000 .80436755 151 SA_REP +08-02 9500 .80436755 152 SA_REP +07-09 9000 .80436755 153 SA_REP +07-01 8000 .80436755 154 SA_REP +06-05 7500 .80436755 155 SA_REP +05-06 7000 .80436755 ... CORR_* The CORR_* functions are: ■ CORR_S ■ CORR_K See Also: "Aggregate Functions" on page 5-8, "About SQL Expressions" on page 6-1 for information on valid forms of expr, and CORR_* on page 5-39 and CORR_S on page 5-40
- 202. CORR_S 5-40 Oracle Database SQL Reference Syntax correlation::= Purpose The CORR function (see CORR on page 5-38) calculates the Pearson's correlation coefficient and requires numeric expressions as input. The CORR_* functions support nonparametric or rank correlation. They let you find correlations between expressions that are ordinal scaled (where ranking of the values is possible). Correlation coefficients take on a value ranging from -1 to 1, where 1 indicates a perfect relationship, -1 a perfect inverse relationship (when one variable increases as the other decreases), and a value close to 0 means no relationship. These functions takes as arguments any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. Oracle Database determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype, makes the calculation, and returns NUMBER. expr1 and expr2 are the two variables being analyzed. The third argument is a return value of type VARCHAR2. If you omit the third argument, the default is COEFFICIENT. The meaning of the return values is shown in the table that follows: CORR_S CORR_S calculates the Spearman's rho correlation coefficient. The input expressions should be a set of (xi, yi) pairs of observations. The function first replaces each value with a rank. Each value of xi is replaced with its rank among all the other xis in the sample, and each value of yi is replaced with its rank among all the other yis. Thus, each xi and yi take on a value from 1 to n, where n is the total number of pairs of values. Ties are assigned the average of the ranks they would have had if their values See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion and "Numeric Precedence" on page 2-13 for information on numeric precedence Table 5–2 CORR_* Return Values Return Value Meaning COEFFICIENT Coefficient of correlation ONE_SIDED_SIG Positive one-tailed significance of the correlation ONE_SIDED_SIG_POS Same as ONE_SIDED_SIG ONE_SIDED_SIG_NEG Negative one-tailed significance of the correlation TWO_SIDED_SIG Two-tailed significance of the correlation CORR_K CORR_S ( expr1 , expr2 , COEFFICIENT ONE_SIDED_SIG ONE_SIDED_SIG_POS ONE_SIDED_SIG_NEG TWO_SIDED_SIG )
- 203. COS Functions 5-41 had been slightly different. Then the function calculates the linear correlation coefficient of the ranks. CORR_S Example Using Spearman's rho correlation coefficient, the following example derives a coefficient of correlation for each of two different comparisons -- salary and commission_pct, and salary and employee_id: SELECT COUNT(*) count, CORR_S(salary, commission_pct) commission, CORR_S(salary, employee_id) empid FROM employees; COUNT COMMISSION EMPID ---------- ---------- ---------- 107 .735837022 -.04482358 CORR_K CORR_K calculates the Kendall's tau-b correlation coefficient. As for CORR_S, the input expressions are a set of (xi, yi) pairs of observations. To calculate the coefficient, the function counts the number of concordant and discordant pairs. A pair of observations is concordant if the observation with the larger x also has a larger value of y. A pair of observations is discordant if the observation with the larger x has a smaller y. The significance of tau-b is the probability that the correlation indicated by tau-b was due to chance--a value of 0 to 1. A small value indicates a significant correlation for positive values of tau-b (or anticorrelation for negative values of tau-b). CORR_K Example Using Kendall's tau-b correlation coefficient, the following example determines whether a correlation exists between an employee's salary and commission percent: SELECT CORR_K(salary, commission_pct, 'COEFFICIENT') coefficient, CORR_K(salary, commission_pct, 'TWO_SIDED_SIG') two_sided_p_value FROM hr.employees; COEFFICIENT TWO_SIDED_P_VALUE ----------- ----------------- .603079768 3.4702E-07 COS Syntax Purpose COS returns the cosine of n (an angle expressed in radians). This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. If the argument is BINARY_ FLOAT, then the function returns BINARY_DOUBLE. Otherwise the function returns the same numeric datatype as the argument. See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion COS ( n )
- 204. COSH 5-42 Oracle Database SQL Reference Examples The following example returns the cosine of 180 degrees: SELECT COS(180 * 3.14159265359/180) "Cosine of 180 degrees" FROM DUAL; Cosine of 180 degrees --------------------- -1 COSH Syntax Purpose COSH returns the hyperbolic cosine of n. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. If the argument is BINARY_ FLOAT, then the function returns BINARY_DOUBLE. Otherwise the function returns the same numeric datatype as the argument. Examples The following example returns the hyperbolic cosine of zero: SELECT COSH(0) "Hyperbolic cosine of 0" FROM DUAL; Hyperbolic cosine of 0 ---------------------- 1 COUNT Syntax Purpose COUNT returns the number of rows returned by the query. You can use it as an aggregate or analytic function. See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions COSH ( n ) COUNT ( * DISTINCT ALL expr ) OVER ( analytic_clause )
- 205. COUNT Functions 5-43 If you specify DISTINCT, then you can specify only the query_partition_clause of the analytic_clause. The order_by_clause and windowing_clause are not allowed. If you specify expr, then COUNT returns the number of rows where expr is not null. You can count either all rows, or only distinct values of expr. If you specify the asterisk (*), then this function returns all rows, including duplicates and nulls. COUNT never returns null. Aggregate Examples The following examples use COUNT as an aggregate function: SELECT COUNT(*) "Total" FROM employees; Total ---------- 107 SELECT COUNT(*) "Allstars" FROM employees WHERE commission_pct > 0; Allstars --------- 35 SELECT COUNT(commission_pct) "Count" FROM employees; Count ---------- 35 SELECT COUNT(DISTINCT manager_id) "Managers" FROM employees; Managers ---------- 18 Analytic Example The following example calculates, for each employee in the employees table, the moving count of employees earning salaries in the range 50 less than through 150 greater than the employee's salary. SELECT last_name, salary, COUNT(*) OVER (ORDER BY salary RANGE BETWEEN 50 PRECEDING AND 150 FOLLOWING) AS mov_count FROM employees; LAST_NAME SALARY MOV_COUNT ------------------------- ---------- ---------- Olson 2100 3 Markle 2200 2 Philtanker 2200 2 Landry 2400 8 Gee 2400 8 Colmenares 2500 10 Patel 2500 10 . . . See Also: "About SQL Expressions" on page 6-1 for information on valid forms of expr and "Aggregate Functions" on page 5-8
- 206. COVAR_POP 5-44 Oracle Database SQL Reference COVAR_POP Syntax Purpose COVAR_POP returns the population covariance of a set of number pairs. You can use it as an aggregate or analytic function. This function takes as arguments any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. Oracle determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype, and returns that datatype. Oracle Database applies the function to the set of (expr1, expr2) pairs after eliminating all pairs for which either expr1 or expr2 is null. Then Oracle makes the following computation: (SUM(expr1 * expr2) - SUM(expr2) * SUM(expr1) / n) / n where n is the number of (expr1, expr2) pairs where neither expr1 nor expr2 is null. The function returns a value of type NUMBER. If the function is applied to an empty set, then it returns null. Aggregate Example The following example calculates the population covariance and sample covariance for time employed (SYSDATE - hire_date) and salary using the sample table hr.employees: SELECT job_id, COVAR_POP(SYSDATE-hire_date, salary) AS covar_pop, COVAR_SAMP(SYSDATE-hire_date, salary) AS covar_samp FROM employees WHERE department_id in (50, 80) GROUP BY job_id; JOB_ID COVAR_POP COVAR_SAMP ---------- ----------- ----------- ST_MAN 436092.000 545115.000 SH_CLERK 782717.500 823913.158 SA_MAN 660700.000 825875.000 SA_REP 579988.466 600702.340 ST_CLERK 176577.250 185870.789 See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion and "Numeric Precedence" on page 2-13 for information on numeric precedence See Also: "About SQL Expressions" on page 6-1 for information on valid forms of expr and "Aggregate Functions" on page 5-8 COVAR_POP ( expr1 , expr2 ) OVER ( analytic_clause )
- 207. COVAR_SAMP Functions 5-45 Analytic Example The following example calculates cumulative sample covariance of the list price and minimum price of the products in the sample schema oe: SELECT product_id, supplier_id, COVAR_POP(list_price, min_price) OVER (ORDER BY product_id, supplier_id) AS CUM_COVP, COVAR_SAMP(list_price, min_price) OVER (ORDER BY product_id, supplier_id) AS CUM_COVS FROM product_information p WHERE category_id = 29 ORDER BY product_id, supplier_id; PRODUCT_ID SUPPLIER_ID CUM_COVP CUM_COVS ---------- ----------- ---------- ---------- 1774 103088 0 1775 103087 1473.25 2946.5 1794 103096 1702.77778 2554.16667 1825 103093 1926.25 2568.33333 2004 103086 1591.4 1989.25 2005 103086 1512.5 1815 2416 103088 1475.97959 1721.97619 . . . COVAR_SAMP Syntax Purpose COVAR_SAMP returns the sample covariance of a set of number pairs. You can use it as an aggregate or analytic function. This function takes as arguments any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. Oracle determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype, and returns that datatype. Oracle Database applies the function to the set of (expr1, expr2) pairs after eliminating all pairs for which either expr1 or expr2 is null. Then Oracle makes the following computation: (SUM(expr1 * expr2) - SUM(expr1) * SUM(expr2) / n) / (n-1) where n is the number of (expr1, expr2) pairs where neither expr1 nor expr2 is null. See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion and "Numeric Precedence" on page 2-13 for information on numeric precedence COVAR_SAMP ( expr1 , expr2 ) OVER ( analytic_clause )
- 208. CUME_DIST 5-46 Oracle Database SQL Reference The function returns a value of type NUMBER. If the function is applied to an empty set, then it returns null. Aggregate Example Please refer to the aggregate example for COVAR_POP on page 5-44. Analytic Example Please refer to the analytic example for COVAR_POP on page 5-44. CUME_DIST Aggregate Syntax cume_dist_aggregate::= Analytic Syntax cume_dist_analytic::= Purpose CUME_DIST calculates the cumulative distribution of a value in a group of values. The range of values returned by CUME_DIST is >0 to <=1. Tie values always evaluate to the same cumulative distribution value. This function takes as arguments any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. Oracle Database determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype, makes the calculation, and returns NUMBER. See Also: "About SQL Expressions" on page 6-1 for information on valid forms of expr and "Aggregate Functions" on page 5-8 See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion and "Numeric Precedence" on page 2-13 for information on numeric precedence CUME_DIST ( expr , ) WITHIN GROUP ( ORDER BY expr DESC ASC NULLS FIRST LAST , ) CUME_DIST ( ) OVER ( query_partition_clause order_by_clause )
- 209. CURRENT_DATE Functions 5-47 ■ As an aggregate function, CUME_DIST calculates, for a hypothetical row r identified by the arguments of the function and a corresponding sort specification, the relative position of row r among the rows in the aggregation group. Oracle makes this calculation as if the hypothetical row r were inserted into the group of rows to be aggregated over. The arguments of the function identify a single hypothetical row within each aggregate group. Therefore, they must all evaluate to constant expressions within each aggregate group. The constant argument expressions and the expressions in the ORDER BY clause of the aggregate match by position. Therefore, the number of arguments must be the same and their types must be compatible. ■ As an analytic function, CUME_DIST computes the relative position of a specified value in a group of values. For a row r, assuming ascending ordering, the CUME_ DIST of r is the number of rows with values lower than or equal to the value of r, divided by the number of rows being evaluated (the entire query result set or a partition). Aggregate Example The following example calculates the cumulative distribution of a hypothetical employee with a salary of $15,500 and commission rate of 5% among the employees in the sample table oe.employees: SELECT CUME_DIST(15500, .05) WITHIN GROUP (ORDER BY salary, commission_pct) "Cume-Dist of 15500" FROM employees; Cume-Dist of 15500 ------------------ .972222222 Analytic Example The following example calculates the salary percentile for each employee in the purchasing division. For example, 40% of clerks have salaries less than or equal to Himuro. SELECT job_id, last_name, salary, CUME_DIST() OVER (PARTITION BY job_id ORDER BY salary) AS cume_dist FROM employees WHERE job_id LIKE 'PU%'; JOB_ID LAST_NAME SALARY CUME_DIST ---------- ------------------------- ---------- ---------- PU_CLERK Colmenares 2500 .2 PU_CLERK Himuro 2600 .4 PU_CLERK Tobias 2800 .6 PU_CLERK Baida 2900 .8 PU_CLERK Khoo 3100 1 PU_MAN Raphaely 11000 1 CURRENT_DATE Syntax CURRENT_DATE
- 210. CURRENT_TIMESTAMP 5-48 Oracle Database SQL Reference Purpose CURRENT_DATE returns the current date in the session time zone, in a value in the Gregorian calendar of datatype DATE. Examples The following example illustrates that CURRENT_DATE is sensitive to the session time zone: ALTER SESSION SET TIME_ZONE = '-5:0'; ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS'; SELECT SESSIONTIMEZONE, CURRENT_DATE FROM DUAL; SESSIONTIMEZONE CURRENT_DATE --------------- -------------------- -05:00 29-MAY-2000 13:14:03 ALTER SESSION SET TIME_ZONE = '-8:0'; SELECT SESSIONTIMEZONE, CURRENT_DATE FROM DUAL; SESSIONTIMEZONE CURRENT_DATE --------------- -------------------- -08:00 29-MAY-2000 10:14:33 CURRENT_TIMESTAMP Syntax Purpose CURRENT_TIMESTAMP returns the current date and time in the session time zone, in a value of datatype TIMESTAMP WITH TIME ZONE. The time zone offset reflects the current local time of the SQL session. If you omit precision, then the default is 6. The difference between this function and LOCALTIMESTAMP is that CURRENT_TIMESTAMP returns a TIMESTAMP WITH TIME ZONE value while LOCALTIMESTAMP returns a TIMESTAMP value. In the optional argument, precision specifies the fractional second precision of the time value returned. Examples The following example illustrates that CURRENT_TIMESTAMP is sensitive to the session time zone: ALTER SESSION SET TIME_ZONE = '-5:0'; ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS'; SELECT SESSIONTIMEZONE, CURRENT_TIMESTAMP FROM DUAL; SESSIONTIMEZONE CURRENT_TIMESTAMP --------------- --------------------------------------------------- -05:00 04-APR-00 01.17.56.917550 PM -05:00 ALTER SESSION SET TIME_ZONE = '-8:0'; See Also: LOCALTIMESTAMP on page 5-89 CURRENT_TIMESTAMP ( precision )
- 211. CV Functions 5-49 SELECT SESSIONTIMEZONE, CURRENT_TIMESTAMP FROM DUAL; SESSIONTIMEZONE CURRENT_TIMESTAMP --------------- ---------------------------------------------------- -08:00 04-APR-00 10.18.21.366065 AM -08:00 If you use the CURRENT_TIMESTAMP with a format mask, take care that the format mask matches the value returned by the function. For example, consider the following table: CREATE TABLE current_test (col1 TIMESTAMP WITH TIME ZONE); The following statement fails because the mask does not include the TIME ZONE portion of the type returned by the function: INSERT INTO current_test VALUES (TO_TIMESTAMP_TZ(CURRENT_TIMESTAMP, 'DD-MON-RR HH.MI.SSXFF PM')); The following statement uses the correct format mask to match the return type of CURRENT_TIMESTAMP: INSERT INTO current_test VALUES (TO_TIMESTAMP_TZ (CURRENT_TIMESTAMP, 'DD-MON-RR HH.MI.SSXFF PM TZH:TZM')); CV Syntax Purpose The CV function can be used only in the model_clause of a SELECT statement and then only on the right-hand side of a model rule. It returns the current value of a dimension column carried from the left-hand side to the right-hand side of a rule. This function is used in the model_clause to provide relative indexing with respect to the dimension column. The return type is that of the datatype of the dimension column. If you omit the argument, it defaults to the dimension column associated with the relative position of the function within the cell reference. The CV function may be used outside a cell reference. In this case, dimension_ column is required. Example The following example assigns the sum of the sales of the product represented by the current value of the dimension column (Mouse Pad or Standard Mouse) for years 1999 and 2000 to the sales of that product for year 2001: SELECT country, prod, year, s FROM sales_view_ref MODEL PARTITION BY (country) DIMENSION BY (prod, year) MEASURES (sale s) See Also: model_clause on page 19-23 and "Model Expressions" on page 6-11 for the syntax and semantics CV ( dimension_column )
- 212. DBTIMEZONE 5-50 Oracle Database SQL Reference IGNORE NAV UNIQUE DIMENSION RULES UPSERT SEQUENTIAL ORDER ( s[FOR prod IN ('Mouse Pad', 'Standard Mouse'), 2001] = s[CV( ), 1999] + s[CV( ), 2000] ) ORDER BY country, prod, year; COUNTRY PROD YEAR S ---------- ----------------------------------- -------- --------- France Mouse Pad 1998 2509.42 France Mouse Pad 1999 3678.69 France Mouse Pad 2000 3000.72 France Mouse Pad 2001 6679.41 France Standard Mouse 1998 2390.83 France Standard Mouse 1999 2280.45 France Standard Mouse 2000 1274.31 France Standard Mouse 2001 3554.76 Germany Mouse Pad 1998 5827.87 Germany Mouse Pad 1999 8346.44 Germany Mouse Pad 2000 7375.46 Germany Mouse Pad 2001 15721.9 Germany Standard Mouse 1998 7116.11 Germany Standard Mouse 1999 6263.14 Germany Standard Mouse 2000 2637.31 Germany Standard Mouse 2001 8900.45 16 rows selected. The preceding example requires the view sales_view_ref. Refer to "The MODEL clause: Examples" on page 19-35 to create this view. DBTIMEZONE Syntax Purpose DBTIMEZONE returns the value of the database time zone. The return type is a time zone offset (a character type in the format '[+|-]TZH:TZM') or a time zone region name, depending on how the user specified the database time zone value in the most recent CREATE DATABASE or ALTER DATABASE statement. Examples The following example assumes that the database time zone is set to UTC time zone: SELECT DBTIMEZONE FROM DUAL; DBTIME ------ +00:00 DBTIMEZONE
- 213. DECODE Functions 5-51 DECODE Syntax Purpose DECODE compares expr to each search value one by one. If expr is equal to a search, then Oracle Database returns the corresponding result. If no match is found, then Oracle returns default. If default is omitted, then Oracle returns null. The arguments can be any of the numeric types (NUMBER, BINARY_FLOAT, or BINARY_DOUBLE) or character types. ■ If expr and search are character data, then Oracle compares them using nonpadded comparison semantics. expr, search, and result can be any of the datatypes CHAR, VARCHAR2, NCHAR, or NVARCHAR2. The string returned is of VARCHAR2 datatype and is in the same character set as the first result parameter. ■ If the first search-result pair are numeric, then Oracle compares all search-result expressions and the first expr to determine the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype, and returns that datatype. The search, result, and default values can be derived from expressions. Oracle Database uses short-circuit evaluation. That is, the database evaluates each search value only before comparing it to expr, rather than evaluating all search values before comparing any of them with expr. Consequently, Oracle never evaluates a search if a previous search is equal to expr. Oracle automatically converts expr and each search value to the datatype of the first search value before comparing. Oracle automatically converts the return value to the same datatype as the first result. If the first result has the datatype CHAR or if the first result is null, then Oracle converts the return value to the datatype VARCHAR2. In a DECODE function, Oracle considers two nulls to be equivalent. If expr is null, then Oracle returns the result of the first search that is also null. The maximum number of components in the DECODE function, including expr, searches, results, and default, is 255. Examples This example decodes the value warehouse_id. If warehouse_id is 1, then the function returns 'Southlake'; if warehouse_id is 2, then it returns 'San Francisco'; and so forth. If warehouse_id is not 1, 2, 3, or 4, then the function returns 'Non domestic'. SELECT product_id, See Also: "Datatype Comparison Rules" on page 2-37 for information on comparison semantics, "Data Conversion" on page 2-40 for information on datatype conversion in general, "Floating-Point Numbers" on page 2-11 for information on floating-point comparison semantics, and "Implicit and Explicit Data Conversion" on page 2-40 for information on the drawbacks of implicit conversion DECODE ( expr , search , result , , default )
- 214. DECOMPOSE 5-52 Oracle Database SQL Reference DECODE (warehouse_id, 1, 'Southlake', 2, 'San Francisco', 3, 'New Jersey', 4, 'Seattle', 'Non domestic') "Location of inventory" FROM inventories WHERE product_id < 1775; DECOMPOSE Syntax Purpose DECOMPOSE is valid only for Unicode characters. DECOMPOSE takes as its argument a string in any datatype and returns a Unicode string after decomposition in the same character set as the input. For example, an o-umlaut code point will be returned as the "o" code point followed by an umlaut code point. ■ string can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. ■ CANONICAL causes canonical decomposition, which allows recomposition (for example, with the COMPOSE function) to the original string. This is the default. ■ COMPATIBILITY causes decomposition in compatibility mode. In this mode, recomposition is not possible. This mode is useful, for example, when decomposing half-width and full-width katakana characters, where recomposition might not be desirable without external formatting or style information. CLOB and NCLOB values are supported through implicit conversion. If char is a character LOB value, it is converted to a VARCHAR value before the COMPOSE operation. The operation will fail if the size of the LOB value exceeds the supported length of the VARCHAR in the particular development environment. Examples The following example ss the string "Châteaux" into its component code points: SELECT DECOMPOSE ('Châteaux') FROM DUAL; DECOMPOSE --------- Cha^teaux See Also: Oracle Database Globalization Support Guide for information on Unicode character sets and character semantics Note: The results of this example can vary depending on the character set of your operating system. DECOMPOSE ( string CANONICAL COMPATIBILITY )
- 215. DELETEXML Functions 5-53 DELETEXML Syntax Purpose DELETEXML deletes the node or nodes matched by the XPath expression in the target XML. ■ XMLType_instance is an instance of XMLType. ■ The XPath_string is an Xpath expression indicating one or more nodes that are to be deleted. You can specify an absolute XPath_string with an initial slash or a relative XPath_string by omitting the initial slash. If you omit the initial slash, the context of the relative path defaults to the root node. Any child nodes of the nodes specified by XPath_string are also deleted. ■ The optional namespace_string provides namespace information for the XPath_string. This parameter must be of type VARCHAR2. Examples The following example removes the /Owner node from the warehouse_spec of one of the warehouses modified in the example for APPENDCHILDXML on page 5-17: UPDATE warehouses SET warehouse_spec = DELETEXML(warehouse_spec, '/Warehouse/Building/Owner') WHERE warehouse_id = 2; SELECT warehouse_id, warehouse_spec FROM warehouses WHERE warehouse_id in (2,3); ID WAREHOUSE_SPEC ---------- ----------------------------------- 2 <?xml version="1.0"?> <Warehouse> <Building>Rented</Building> <Area>50000</Area> <Docks>1</Docks> <DockType>Side load</DockType> <WaterAccess>Y</WaterAccess> <RailAccess>N</RailAccess> <Parking>Lot</Parking> <VClearance>12 ft</VClearance> </Warehouse> 3 <?xml version="1.0"?> <Warehouse> <Building>Rented <Owner>Grandco</Owner> <Owner>ThirdOwner</Owner> <Owner>LesserCo</Owner> </Building> See Also: Oracle XML DB Developer's Guide for more information about this function DELETEXML ( XMLType_instance , XPath_string , namespace_string )
- 216. DENSE_RANK 5-54 Oracle Database SQL Reference <Area>85700</Area> <DockType/> <WaterAccess>N</WaterAccess> <RailAccess>N</RailAccess> <Parking>Street</Parking> <VClearance>11.5 ft</VClearance> </Warehouse> DENSE_RANK Aggregate Syntax dense_rank_aggregate::= Analytic Syntax dense_rank_analytic::= Purpose DENSE_RANK computes the rank of a row in an ordered group of rows and returns the rank as a NUMBER. The ranks are consecutive integers beginning with 1. The largest rank value is the number of unique values returned by the query. Rank values are not skipped in the event of ties. Rows with equal values for the ranking criteria receive the same rank. This function is useful for top-N and bottom-N reporting. This function accepts as arguments any numeric datatype and returns NUMBER. ■ As an aggregate function, DENSE_RANK calculates the dense rank of a hypothetical row identified by the arguments of the function with respect to a given sort specification. The arguments of the function must all evaluate to constant expressions within each aggregate group, because they identify a single row within each group. The constant argument expressions and the expressions in the order_by_clause of the aggregate match by position. Therefore, the number of arguments must be the same and types must be compatible. ■ As an analytic function, DENSE_RANK computes the rank of each row returned from a query with respect to the other rows, based on the values of the value_ exprs in the order_by_clause. See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions DENSE_RANK ( expr , ) WITHIN GROUP ( ORDER BY expr DESC ASC NULLS FIRST LAST , ) DENSE_RANK ( ) OVER ( query_partition_clause order_by_clause )
- 217. DEPTH Functions 5-55 Aggregate Example The following example computes the ranking of a hypothetical employee with the salary $15,500 and a commission of 5% in the sample table oe.employees: SELECT DENSE_RANK(15500, .05) WITHIN GROUP (ORDER BY salary DESC, commission_pct) "Dense Rank" FROM employees; Dense Rank ------------------- 3 Analytic Example The following statement selects the department name, employee name, and salary of all employees who work in the human resources or purchasing department, and then computes a rank for each unique salary in each of the two departments. The salaries that are equal receive the same rank. Compare this example with the example for RANK on page 5-131. SELECT d.department_name, e.last_name, e.salary, DENSE_RANK() OVER (PARTITION BY e.department_id ORDER BY e.salary) AS drank FROM employees e, departments d WHERE e.department_id = d.department_id AND d.department_id IN ('30', '40'); DEPARTMENT_NAME LAST_NAME SALARY DRANK ----------------------- ------------------ ---------- ---------- Purchasing Colmenares 2500 1 Purchasing Himuro 2600 2 Purchasing Tobias 2800 3 Purchasing Baida 2900 4 Purchasing Khoo 3100 5 Purchasing Raphaely 11000 6 Human Resources Marvis 6500 DEPTH Syntax Purpose DEPTH is an ancillary function used only with the UNDER_PATH and EQUALS_PATH conditions. It returns the number of levels in the path specified by the UNDER_PATH condition with the same correlation variable. The correlation_integer can be any NUMBER integer. Use it to correlate this ancillary function with its primary condition if the statement contains multiple primary conditions. Values less than 1 are treated as 1. Examples The EQUALS_PATH and UNDER_PATH conditions can take two ancillary functions, DEPTH and PATH. The following example shows the use of both ancillary functions. See Also: EQUALS_PATH Condition on page 7-19, UNDER_PATH Condition on page 7-20, and the related function PATH on page 5-112 DEPTH ( correlation_integer )
- 218. DEREF 5-56 Oracle Database SQL Reference The example assumes the existence of the XMLSchema warehouses.xsd (created in "Using XML in SQL Statements" on page E-8). SELECT PATH(1), DEPTH(2) FROM RESOURCE_VIEW WHERE UNDER_PATH(res, '/sys/schemas/OE', 1)=1 AND UNDER_PATH(res, '/sys/schemas/OE', 2)=1; PATH(1) DEPTH(2) -------------------------------- -------- /www.oracle.com 1 /www.oracle.com/xwarehouses.xsd 2 DEREF Syntax Purpose DEREF returns the object reference of argument expr, where expr must return a REF to an object. If you do not use this function in a query, then Oracle Database returns the object ID of the REF instead, as shown in the example that follows. Examples The sample schema oe contains an object type cust_address_typ. The "REF Constraint Examples" on page 8-24 create a similar type, cust_address_typ_new, and a table with one column that is a REF to the type. The following example shows how to insert into such a column and how to use DEREF to extract information from the column: INSERT INTO address_table VALUES ('1 First', 'G45 EU8', 'Paris', 'CA', 'US'); INSERT INTO customer_addresses SELECT 999, REF(a) FROM address_table a; SELECT address FROM customer_addresses; ADDRESS -------------------------------------------------------------------------------- 000022020876B2245DBE325C5FE03400400B40DCB176B2245DBE305C5FE03400400B40DCB1 SELECT DEREF(address) FROM customer_addresses; DEREF(ADDRESS)(STREET_ADDRESS, POSTAL_CODE, CITY, STATE_PROVINCE, COUNTRY_ID) -------------------------------------------------------------------------------- CUST_ADDRESS_TYP('1 First', 'G45 EU8', 'Paris', 'CA', 'US') See Also: MAKE_REF on page 5-92 DEREF ( expr )
- 219. DUMP Functions 5-57 DUMP Syntax Purpose DUMP returns a VARCHAR2 value containing the datatype code, length in bytes, and internal representation of expr. The returned result is always in the database character set. For the datatype corresponding to each code, see Table 2–2, " Storage of Scale and Precision" on page 2-11. The argument return_fmt specifies the format of the return value and can have any of the following values: ■ 8 returns result in octal notation. ■ 10 returns result in decimal notation. ■ 16 returns result in hexadecimal notation. ■ 17 returns result as single characters. By default, the return value contains no character set information. To retrieve the character set name of expr, add 1000 to any of the preceding format values. For example, a return_fmt of 1008 returns the result in octal and provides the character set name of expr. The arguments start_position and length combine to determine which portion of the internal representation to return. The default is to return the entire internal representation in decimal notation. If expr is null, then this function returns NULL. This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion. Examples The following examples show how to extract dump information from a string expression and a column: SELECT DUMP('abc', 1016) FROM DUAL; DUMP('ABC',1016) ------------------------------------------ Typ=96 Len=3 CharacterSet=WE8DEC: 61,62,63 SELECT DUMP(last_name, 8, 3, 2) "OCTAL" FROM employees WHERE last_name = 'Hunold'; See Also: "Datatype Comparison Rules" on page 2-37 for more information DUMP ( expr , return_fmt , start_position , length )
- 220. EMPTY_BLOB, EMPTY_CLOB 5-58 Oracle Database SQL Reference OCTAL ------------------------------------------------------------------- Typ=1 Len=6: 156,157 SELECT DUMP(last_name, 10, 3, 2) "ASCII" FROM employees WHERE last_name = 'Hunold'; ASCII -------------------------------------------------------------------- Typ=1 Len=6: 110,111 EMPTY_BLOB, EMPTY_CLOB Syntax empty_LOB::= Purpose EMPTY_BLOB and EMPTY_CLOB return an empty LOB locator that can be used to initialize a LOB variable or, in an INSERT or UPDATE statement, to initialize a LOB column or attribute to EMPTY. EMPTY means that the LOB is initialized, but not populated with data. Restriction on LOB Locators You cannot use the locator returned from this function as a parameter to the DBMS_LOB package or the OCI. Examples The following example initializes the ad_photo column of the sample pm.print_ media table to EMPTY: UPDATE print_media SET ad_photo = EMPTY_BLOB(); EXISTSNODE Syntax Purpose EXISTSNODE determines whether traversal of an XML document using a specified path results in any nodes. It takes as arguments the XMLType instance containing an XML document and a VARCHAR2 XPath string designating a path. The optional namespace_string must resolve to a VARCHAR2 value that specifies a default mapping or namespace mapping for prefixes, which Oracle Database uses when evaluating the XPath expression(s). EMPTY_BLOB EMPTY_CLOB ( ) EXISTSNODE ( XMLType_instance , XPath_string , namespace_string )
- 221. EXP Functions 5-59 The namespace_string argument defaults to the namespace of the root element. If you refer to any subelement in Xpath_string, then you must specify namespace_ string, and you must specify the "who" prefix in both of these arguments. The return value is NUMBER: ■ 0 if no nodes remain after applying the XPath traversal on the document ■ 1 if any nodes remain Examples The following example tests for the existence of the /Warehouse/Dock node in the XML path of the warehouse_spec column of the sample table oe.warehouses: SELECT warehouse_id, warehouse_name FROM warehouses WHERE EXISTSNODE(warehouse_spec, '/Warehouse/Docks') = 1; WAREHOUSE_ID WAREHOUSE_NAME ------------ ----------------------------------- 1 Southlake, Texas 2 San Francisco 4 Seattle, Washington EXP Syntax Purpose EXP returns e raised to the nth power, where e = 2.71828183 ... The function returns a value of the same type as the argument. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. If the argument is BINARY_ FLOAT, then the function returns BINARY_DOUBLE. Otherwise the function returns the same numeric datatype as the argument. Examples The following example returns e to the 4th power: SELECT EXP(4) "e to the 4th power" FROM DUAL; e to the 4th power ------------------ 54.59815 See Also: "Using XML in SQL Statements" on page E-8 for examples that specify namespace_string and use the "who" prefix. See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion EXP ( n )
- 222. EXTRACT (datetime) 5-60 Oracle Database SQL Reference EXTRACT (datetime) Syntax extract_datetime::= Purpose EXTRACT extracts and returns the value of a specified datetime field from a datetime or interval value expression. When you extract a TIMEZONE_REGION or TIMEZONE_ ABBR (abbreviation), the value returned is a string containing the appropriate time zone name or abbreviation. When you extract any of the other values, the value returned is in the Gregorian calendar. When extracting from a datetime with a time zone value, the value returned is in UTC. For a listing of time zone names and their corresponding abbreviations, query the V$TIMEZONE_NAMES dynamic performance view. This function can be very useful for manipulating datetime field values in very large tables, as shown in the first example below. Some combinations of datetime field and datetime or interval value expression result in ambiguity. In these cases, Oracle Database returns UNKNOWN (see the examples that follow for additional information). The field you are extracting must be a field of the datetime_value_expr or interval_value_expr. For example, you can extract only YEAR, MONTH, and DAY from a DATE value. Likewise, you can extract TIMEZONE_HOUR and TIMEZONE_ MINUTE only from the TIMESTAMP WITH TIME ZONE datatype. Note: Timezone region names are needed by the daylight savings feature. The region names are stored in two time zone files. The default time zone file is a small file containing only the most common time zones to maximize performance. If your time zone is not in the default file, then you will not have daylight savings support until you provide a path to the complete (larger) file by way of the ORA_TZFILE environment variable. EXTRACT ( YEAR MONTH DAY HOUR MINUTE SECOND TIMEZONE_HOUR TIMEZONE_MINUTE TIMEZONE_REGION TIMEZONE_ABBR FROM datetime_value_expression interval_value_expression )
- 223. EXTRACT (datetime) Functions 5-61 Examples The following example returns from the oe.orders table the number of orders placed in each month: SELECT EXTRACT(month FROM order_date) "Month", COUNT(order_date) "No. of Orders" FROM orders GROUP BY EXTRACT(month FROM order_date) ORDER BY "No. of Orders" DESC; Month No. of Orders ---------- ------------- 11 15 7 14 6 14 3 11 5 10 9 9 2 9 8 7 10 6 1 5 12 4 4 1 12 rows selected. The following example returns the year 1998. SELECT EXTRACT(YEAR FROM DATE '1998-03-07') FROM DUAL; EXTRACT(YEARFROMDATE'1998-03-07') --------------------------------- 1998 The following example selects from the sample table hr.employees all employees who were hired after 1998: SELECT last_name, employee_id, hire_date FROM employees WHERE EXTRACT(YEAR FROM TO_DATE(hire_date, 'DD-MON-RR')) > 1998 ORDER BY hire_date; LAST_NAME EMPLOYEE_ID HIRE_DATE ------------------------- ----------- --------- Landry 127 14-JAN-99 See Also: ■ Oracle Database Administrator's Guide for more information about setting the ORA_TZFILE environment variable ■ Oracle Database Globalization Support Guide. for a complete listing of the timezone region names in both files ■ "Datetime/Interval Arithmetic" on page 2-19 for a description of datetime_value_expr and interval_value_expr ■ Oracle Database Reference for information on the dynamic performance views
- 224. EXTRACT (XML) 5-62 Oracle Database SQL Reference Lorentz 107 07-FEB-99 Cabrio 187 07-FEB-99 . . . The following example results in ambiguity, so Oracle returns UNKNOWN: SELECT EXTRACT(TIMEZONE_REGION FROM TIMESTAMP '1999-01-01 10:00:00 -08:00') FROM DUAL; EXTRACT(TIMEZONE_REGIONFROMTIMESTAMP'1999-01-0110:00:00-08:00') ---------------------------------------------------------------- UNKNOWN The ambiguity arises because the time zone numerical offset is provided in the expression, and that numerical offset may map to more than one time zone region. EXTRACT (XML) Syntax extract_xml::= Purpose EXTRACT (XML) is similar to the EXISTSNODE function. It applies a VARCHAR2 XPath string and returns an XMLType instance containing an XML fragment. You can specify an absolute XPath_string with an initial slash or a relative XPath_string by omitting the initial slash. If you omit the initial slash, the context of the relative path defaults to the root node. The optional namespace_string must resolve to a VARCHAR2 value that specifies a default mapping or namespace mapping for prefixes, which Oracle Database uses when evaluating the XPath expression(s). Examples The following example extracts the value of the /Warehouse/Dock node of the XML path of the warehouse_spec column in the sample table oe.warehouses: SELECT warehouse_name, EXTRACT(warehouse_spec, '/Warehouse/Docks') "Number of Docks" FROM warehouses WHERE warehouse_spec IS NOT NULL; WAREHOUSE_NAME Number of Docks -------------------- -------------------- Southlake, Texas <Docks>2</Docks> San Francisco <Docks>1</Docks> New Jersey <Docks/> Seattle, Washington <Docks>3</Docks> Compare this example with the example for EXTRACTVALUE on page 5-63, which returns the scalar value of the XML fragment. EXTRACT ( XMLType_instance , XPath_string , namespace_string )
- 225. FEATURE_ID Functions 5-63 EXTRACTVALUE Syntax The EXTRACTVALUE function takes as arguments an XMLType instance and an XPath expression and returns a scalar value of the resultant node. The result must be a single node and be either a text node, attribute, or element. If the result is an element, then the element must have a single text node as its child, and it is this value that the function returns. You can specify an absolute XPath_string with an initial slash or a relative XPath_string by omitting the initial slash. If you omit the initial slash, the context of the relative path defaults to the root node. If the specified XPath points to a node with more than one child, or if the node pointed to has a non-text node child, then Oracle returns an error. The optional namespace_ string must resolve to a VARCHAR2 value that specifies a default mapping or namespace mapping for prefixes, which Oracle uses when evaluating the XPath expression(s). For documents based on XML schemas, if Oracle can infer the type of the return value, then a scalar value of the appropriate type is returned. Otherwise, the result is of type VARCHAR2. For documents that are not based on XML schemas, the return type is always VARCHAR2. Examples The following example takes as input the same arguments as the example for EXTRACT (XML) on page 5-62. Instead of returning an XML fragment, as does the EXTRACT function, it returns the scalar value of the XML fragment: SELECT warehouse_name, EXTRACTVALUE(e.warehouse_spec, '/Warehouse/Docks') "Docks" FROM warehouses e WHERE warehouse_spec IS NOT NULL; WAREHOUSE_NAME Docks -------------------- ------------ Southlake, Texas 2 San Francisco 1 New Jersey Seattle, Washington 3 FEATURE_ID Syntax EXTRACTVALUE ( XMLType_instance , XPath_string , namespace_string ) FEATURE_ID ( schema . model mining_attribute_clause )
- 226. FEATURE_ID 5-64 Oracle Database SQL Reference mining_attribute_clause:= Purpose This function is for use with feature extraction models that have been created using the DBMS_DATA_MINING package or with the Oracle Data Mining Java API. It returns an Oracle NUMBER that is the identifier of the feature with the highest coefficient value. The mining_attribute_clause behaves as described for the PREDICTION function. Please refer to mining_attribute_clause on page 5-121. Examples The following example lists the features and corresponding count of customers in a dataset. This example and the prerequisite data mining operations, including creation of the nmf_sh_sample model and nmf_sh_sample_apply_prepared view, can be found in the demo file $ORACLE_HOME/rdbms/demo/dmnmdemo.sql. General information on data mining demo files is available in Oracle Data Mining Administrator's Guide. The example is presented here to illustrate the syntactic use of the function. SELECT FEATURE_ID(nmf_sh_sample USING *) AS feat, COUNT(*) AS cnt FROM nmf_sh_sample_apply_prepared GROUP BY FEATURE_ID(nmf_sh_sample USING *) ORDER BY cnt DESC; FEAT CNT ---------- ---------- 7 1443 2 49 3 6 1 1 6 1 See Also: ■ Oracle Data Mining Concepts for detailed information on Oracle Data Mining features ■ Oracle Data Mining Administrator's Guide for information on the demo programs available in the code ■ Oracle Data Mining Application Developer's Guide for information on writing Oracle Data Mining applications USING * schema . table . * expr AS alias ,
- 227. FEATURE_SET Functions 5-65 FEATURE_SET Syntax mining_attribute_clause:= Purpose This function is for use with feature extraction models that have been created using the DBMS_DATA_MINING package or with the Oracle Data Mining Java API. It returns a varray of objects containing all possible features. Each object in the varray is a pair of scalar values containing the feature ID and the feature value. The object fields are named FEATURE_ID and VALUE, and both are Oracle NUMBER. The optional topN argument is a positive integer that restricts the set of features to those that have one of the top N values. If there is a tie at the Nth value, the database still returns only N values. If you omit this argument, then the function returns all features. The optional cutoff argument restricts the returned features to only those that have a feature value greater than or equal to the specified cutoff. To filter only by cutoff, specify NULL for topN and the desired cutoff for cutoff. The mining_attribute_clause behaves as described for the PREDICTION function. Please refer to mining_attribute_clause on page 5-121. Examples The following example lists the top features corresponding to a given customer record (based on match quality), and determines the top attributes for each feature (based on coefficient > 0.25). This example and the prerequisite data mining operations, including the creation of the model, views, and type, can be found in the demo file $ORACLE_ HOME/rdbms/demo/dmnmdemo.sql. General information on data mining demo files See Also: ■ Oracle Data Mining Concepts for detailed information on Oracle Data Mining features ■ Oracle Data Mining Administrator's Guide for information on the demo programs available in the code ■ Oracle Data Mining Application Developer's Guide for information on writing Oracle Data Mining applications FEATURE_SET ( schema . model , topN , cutoff mining_attribute_clause ) USING * schema . table . * expr AS alias ,
- 228. FEATURE_SET 5-66 Oracle Database SQL Reference is available in Oracle Data Mining Administrator's Guide. The example is presented here to illustrate the syntactic use of the function. WITH feat_tab AS ( SELECT F.feature_id fid, A.attribute_name attr, TO_CHAR(A.attribute_value) val, A.coefficient coeff FROM TABLE(DBMS_DATA_MINING.GET_MODEL_DETAILS_NMF('nmf_sh_sample')) F, TABLE(F.attribute_set) A WHERE A.coefficient > 0.25 ), feat AS ( SELECT fid, CAST(COLLECT(Featattr(attr, val, coeff)) AS Featattrs) f_attrs FROM feat_tab GROUP BY fid ), cust_10_features AS ( SELECT T.cust_id, S.feature_id, S.value FROM (SELECT cust_id, FEATURE_SET(nmf_sh_sample, 10 USING *) pset FROM nmf_sh_sample_apply_prepared WHERE cust_id = 100002) T, TABLE(T.pset) S ) SELECT A.value, A.feature_id fid, B.attr, B.val, B.coeff FROM cust_10_features A, (SELECT T.fid, F.* FROM feat T, TABLE(T.f_attrs) F) B WHERE A.feature_id = B.fid ORDER BY A.value DESC, A.feature_id ASC, coeff DESC, attr ASC, val ASC; VALUE FID ATTR VAL COEFF -------- ---- ------------------------- -------------------- ------- 6.8409 7 YRS_RESIDENCE 1.3879 6.8409 7 BOOKKEEPING_APPLICATION .4388 6.8409 7 CUST_GENDER M .2956 6.8409 7 COUNTRY_NAME United States of Ame .2848 rica 6.4975 3 YRS_RESIDENCE 1.2668 6.4975 3 BOOKKEEPING_APPLICATION .3465 6.4975 3 COUNTRY_NAME United States of Ame .2927 rica 6.4886 2 YRS_RESIDENCE 1.3285 6.4886 2 CUST_GENDER M .2819 6.4886 2 PRINTER_SUPPLIES .2704 6.3953 4 YRS_RESIDENCE 1.2931 5.9640 6 YRS_RESIDENCE 1.1585 5.9640 6 HOME_THEATER_PACKAGE .2576 5.2424 5 YRS_RESIDENCE 1.0067 2.4714 8 YRS_RESIDENCE .3297 2.3559 1 YRS_RESIDENCE .2768 2.3559 1 FLAT_PANEL_MONITOR .2593 17 rows selected.
- 229. FEATURE_VALUE Functions 5-67 FEATURE_VALUE Syntax mining_attribute_clause:= Purpose This function is for use with feature extraction models that have been created using the DBMS_DATA_MINING package or with the Oracle Data Mining Java API. It returns the value of a given feature. If you omit the feature_id argument, then the function returns the highest feature value. You can use this form in conjunction with the FEATURE_ID function to obtain the largest feature/value combination. The mining_attribute_clause behaves as described for the PREDICTION function. Please refer to mining_attribute_clause on page 5-121. Examples The following example lists the customers that correspond to feature 3, ordered by match quality. This example and the prerequisite data mining operations, including the creation of the model and view, can be found in the demo file $ORACLE_ HOME/rdbms/demo/dmnmdemo.sql. General information on data mining demo files is available in Oracle Data Mining Administrator's Guide. The example is presented here to illustrate the syntactic use of the function. SELECT * FROM (SELECT cust_id, FEATURE_VALUE(nmf_sh_sample, 3 USING *) match_quality FROM nmf_sh_sample_apply_prepared ORDER BY match_quality DESC) WHERE ROWNUM < 11; CUST_ID MATCH_QUALITY ---------- ------------- 100210 19.4101627 See Also: ■ Oracle Data Mining Concepts for detailed information on Oracle Data Mining features ■ Oracle Data Mining Administrator's Guide for information on the demo programs available in the code ■ Oracle Data Mining Application Developer's Guide for information on writing Oracle Data Mining applications FEATURE_VALUE ( schema . model , feature_id mining_attribute_clause ) USING * schema . table . * expr AS alias ,
- 230. FIRST 5-68 Oracle Database SQL Reference 100962 15.2482251 101151 14.5685197 101499 14.4186292 100363 14.4037396 100372 14.3335148 100982 14.1716545 101039 14.1079914 100759 14.0913761 100953 14.0799737 10 rows selected. FIRST Syntax first::= Purpose FIRST and LAST are very similar functions. Both are aggregate and analytic functions that operate on a set of values from a set of rows that rank as the FIRST or LAST with respect to a given sorting specification. If only one row ranks as FIRST or LAST, the aggregate operates on the set with only one element. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument. When you need a value from the first or last row of a sorted group, but the needed value is not the sort key, the FIRST and LAST functions eliminate the need for self-joins or views and enable better performance. ■ The aggregate_function is any one of the MIN, MAX, SUM, AVG, COUNT, VARIANCE, or STDDEV functions. It operates on values from the rows that rank either FIRST or LAST. If only one row ranks as FIRST or LAST, the aggregate operates on a singleton (nonaggregate) set. ■ The KEEP keyword is for semantic clarity. It qualifies aggregate_function, indicating that only the FIRST or LAST values of aggregate_function will be returned. See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions of the ORDER BY clause and OVER clause aggregate_function KEEP ( DENSE_RANK FIRST ORDER BY expr DESC ASC NULLS FIRST LAST , ) OVER query_partition_clause
- 231. FIRST Functions 5-69 ■ DENSE_RANK FIRST or DENSE_RANK LAST indicates that Oracle Database will aggregate over only those rows with the minimum (FIRST) or the maximum (LAST) dense rank (also called olympic rank). You can use the FIRST and LAST functions as analytic functions by specifying the OVER clause. The query_partitioning_clause is the only part of the OVER clause valid with these functions. Aggregate Example The following example returns, within each department of the sample table hr.employees, the minimum salary among the employees who make the lowest commission and the maximum salary among the employees who make the highest commission: SELECT department_id, MIN(salary) KEEP (DENSE_RANK FIRST ORDER BY commission_pct) "Worst", MAX(salary) KEEP (DENSE_RANK LAST ORDER BY commission_pct) "Best" FROM employees GROUP BY department_id; DEPARTMENT_ID Worst Best ------------- ---------- ---------- 10 4400 4400 20 6000 13000 30 2500 11000 40 6500 6500 50 2100 8200 60 4200 9000 70 10000 10000 80 6100 14000 90 17000 24000 100 6900 12000 110 8300 12000 7000 7000 Analytic Example The next example makes the same calculation as the previous example but returns the result for each employee within the department: SELECT last_name, department_id, salary, MIN(salary) KEEP (DENSE_RANK FIRST ORDER BY commission_pct) OVER (PARTITION BY department_id) "Worst", MAX(salary) KEEP (DENSE_RANK LAST ORDER BY commission_pct) OVER (PARTITION BY department_id) "Best" FROM employees ORDER BY department_id, salary; LAST_NAME DEPARTMENT_ID SALARY Worst Best ------------------- ------------- ---------- ---------- ---------- Whalen 10 4400 4400 4400 Fay 20 6000 6000 13000 Hartstein 20 13000 6000 13000 . . . Gietz 110 8300 8300 12000 Higgins 110 12000 8300 12000 See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion and LAST on page 5-82
- 232. FIRST_VALUE 5-70 Oracle Database SQL Reference Grant 7000 7000 7000 FIRST_VALUE Syntax Purpose FIRST_VALUE is an analytic function. It returns the first value in an ordered set of values. If the first value in the set is null, then the function returns NULL unless you specify IGNORE NULLS. This setting is useful for data densification. If you specify IGNORE NULLS, then FIRST_VALUE returns the fist non-null value in the set, or NULL if all values are null. Please refer to "Using Partitioned Outer Joins: Examples" on page 19-41 for an example of data densification. You cannot use FIRST_VALUE or any other analytic function for expr. That is, you cannot nest analytic functions, but you can use other built-in function expressions for expr. Please refer to "About SQL Expressions" on page 6-1 for information on valid forms of expr. Examples The following example selects, for each employee in Department 90, the name of the employee with the lowest salary. SELECT department_id, last_name, salary, FIRST_VALUE(last_name) OVER (ORDER BY salary ASC ROWS UNBOUNDED PRECEDING) AS lowest_sal FROM (SELECT * FROM employees WHERE department_id = 90 ORDER BY employee_id); DEPARTMENT_ID LAST_NAME SALARY LOWEST_SAL ------------- ------------- ---------- ------------------------- 90 Kochhar 17000 Kochhar 90 De Haan 17000 Kochhar 90 King 24000 Kochhar The example illustrates the nondeterministic nature of the FIRST_VALUE function. Kochhar and DeHaan have the same salary, so are in adjacent rows. Kochhar appears first because the rows returned by the subquery are ordered by employee_id. However, if the rows returned by the subquery are ordered by employee_id in descending order, as in the next example, then the function returns a different value: SELECT department_id, last_name, salary, FIRST_VALUE(last_name) OVER (ORDER BY salary ASC ROWS UNBOUNDED PRECEDING) as fv FROM (SELECT * FROM employees WHERE department_id = 90 ORDER by employee_id DESC); DEPARTMENT_ID LAST_NAME SALARY FV ------------- ------------- ---------- ------------------------- 90 De Haan 17000 De Haan 90 Kochhar 17000 De Haan 90 King 24000 De Haan See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions, including valid forms of expr FIRST_VALUE ( expr IGNORE NULLS ) OVER ( analytic_clause )
- 233. FROM_TZ Functions 5-71 The following example shows how to make the FIRST_VALUE function deterministic by ordering on a unique key. SELECT department_id, last_name, salary, hire_date, FIRST_VALUE(last_name) OVER (ORDER BY salary ASC, hire_date ROWS UNBOUNDED PRECEDING) AS fv FROM (SELECT * FROM employees WHERE department_id = 90 ORDER BY employee_id DESC); DEPARTMENT_ID LAST_NAME SALARY HIRE_DATE FV ------------- ------------- ---------- --------- --------------- 90 Kochhar 17000 21-SEP-89 Kochhar 90 De Haan 17000 13-JAN-93 Kochhar 90 King 24000 17-JUN-87 Kochhar FLOOR Syntax Purpose FLOOR returns largest integer equal to or less than n. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument. Examples The following example returns the largest integer equal to or less than 15.7: SELECT FLOOR(15.7) "Floor" FROM DUAL; Floor ---------- 15 FROM_TZ Syntax Purpose FROM_TZ converts a timestamp value and a time zone to a TIMESTAMP WITH TIME ZONE value. time_zone_value is a character string in the format 'TZH:TZM' or a character expression that returns a string in TZR with optional TZD format. Examples The following example returns a timestamp value to TIMESTAMP WITH TIME ZONE: See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion FLOOR ( n ) FROM_TZ ( timestamp_value , time_zone_value )
- 234. GREATEST 5-72 Oracle Database SQL Reference SELECT FROM_TZ(TIMESTAMP '2000-03-28 08:00:00', '3:00') FROM DUAL; FROM_TZ(TIMESTAMP'2000-03-2808:00:00','3:00') --------------------------------------------------------------- 28-MAR-00 08.00.00 AM +03:00 GREATEST Syntax Purpose GREATEST returns the greatest of the list of one or more expressions. Oracle Database uses the first expr to determine the return type. If the first expr is numeric, then Oracle determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype before the comparison, and returns that datatype. If the first expr is not numeric, then each expr after the first is implicitly converted to the datatype of the first expr before the comparison. Oracle Database compares each expr using nonpadded comparison semantics. The comparison is binary by default and is linguistic if the NLS_COMP parameter is set to LINGUISTIC. Character comparison is based on the numerical codes of the characters in the database character set and is performed on whole strings treated as one sequence of bytes, rather than character by character. If the value returned by this function is character data, then its datatype is always VARCHAR2. Examples The following statement selects the string with the greatest value: SELECT GREATEST ('HARRY', 'HARRIOT', 'HAROLD') "Greatest" FROM DUAL; Greatest -------- HARRY GROUP_ID Syntax See Also: ■ "Datatype Comparison Rules" on page 2-37 for more information on character comparison ■ Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion and "Floating-Point Numbers" on page 2-11 for information on binary-float comparison semantics GREATEST ( expr , ) GROUP_ID ( )
- 235. GROUPING Functions 5-73 Purpose GROUP_ID distinguishes duplicate groups resulting from a GROUP BY specification. It is useful in filtering out duplicate groupings from the query result. It returns an Oracle NUMBER to uniquely identify duplicate groups. This function is applicable only in a SELECT statement that contains a GROUP BY clause. If n duplicates exist for a particular grouping, then GROUP_ID returns numbers in the range 0 to n-1. Examples The following example assigns the value 1 to the duplicate co.country_region grouping from a query on the sample tables sh.countries and sh.sales: SELECT co.country_region, co.country_subregion, SUM(s.amount_sold) "Revenue", GROUP_ID() g FROM sales s, customers c, countries co WHERE s.cust_id = c.cust_id AND c.country_id = co.country_id AND s.time_id = '1-JAN-00' AND co.country_region IN ('Americas', 'Europe') GROUP BY co.country_region, ROLLUP (co.country_region, co.country_subregion); COUNTRY_REGION COUNTRY_SUBREGION Revenue G -------------------- -------------------- ---------- ---------- Americas Northern America 220844 0 Americas Southern America 10872 0 Europe Eastern Europe 12751 0 Europe Western Europe 558686 0 Americas 231716 0 Europe 571437 0 Americas 231716 1 Europe 571437 1 To ensure that only rows with GROUP_ID < 1 are returned, add the following HAVING clause to the end of the statement : HAVING GROUP_ID() < 1 GROUPING Syntax Purpose GROUPING distinguishes superaggregate rows from regular grouped rows. GROUP BY extensions such as ROLLUP and CUBE produce superaggregate rows where the set of all values is represented by null. Using the GROUPING function, you can distinguish a null representing the set of all values in a superaggregate row from a null in a regular row. The expr in the GROUPING function must match one of the expressions in the GROUP BY clause. The function returns a value of 1 if the value of expr in the row is a null representing the set of all values. Otherwise, it returns zero. The datatype of the value GROUPING ( expr )
- 236. GROUPING_ID 5-74 Oracle Database SQL Reference returned by the GROUPING function is Oracle NUMBER. Please refer to the SELECT group_by_clause on page 19-21 for a discussion of these terms. Examples In the following example, which uses the sample tables hr.departments and hr.employees, if the GROUPING function returns 1 (indicating a superaggregate row rather than a regular row from the table), then the string "All Jobs" appears in the "JOB" column instead of the null that would otherwise appear: SELECT DECODE(GROUPING(department_name), 1, 'All Departments', department_name) AS department, DECODE(GROUPING(job_id), 1, 'All Jobs', job_id) AS job, COUNT(*) "Total Empl", AVG(salary) * 12 "Average Sal" FROM employees e, departments d WHERE d.department_id = e.department_id GROUP BY ROLLUP (department_name, job_id); DEPARTMENT JOB Total Empl Average Sal ------------------------------ ---------- ---------- ----------- Accounting AC_ACCOUNT 1 99600 Accounting AC_MGR 1 144000 Accounting All Jobs 2 121800 Administration AD_ASST 1 52800 Administration All Jobs 1 52800 Executive AD_PRES 1 288000 Executive AD_VP 2 204000 Executive All Jobs 3 232000 Finance FI_ACCOUNT 5 95040 Finance FI_MGR 1 144000 Finance All Jobs 6 103200 . . . GROUPING_ID Syntax Purpose GROUPING_ID returns a number corresponding to the GROUPING bit vector associated with a row. GROUPING_ID is applicable only in a SELECT statement that contains a GROUP BY extension, such as ROLLUP or CUBE, and a GROUPING function. In queries with many GROUP BY expressions, determining the GROUP BY level of a particular row requires many GROUPING functions, which leads to cumbersome SQL. GROUPING_ID is useful in these cases. GROUPING_ID is functionally equivalent to taking the results of multiple GROUPING functions and concatenating them into a bit vector (a string of ones and zeros). By using GROUPING_ID you can avoid the need for multiple GROUPING functions and make row filtering conditions easier to express. Row filtering is easier with GROUPING_ID because the desired rows can be identified with a single condition of GROUPING_ID = n. The function is especially useful when storing multiple levels of aggregation in a single table. GROUPING_ID ( expr , )
- 237. HEXTORAW Functions 5-75 Examples The following example shows how to extract grouping IDs from a query of the sample table sh.sales: SELECT channel_id, promo_id, sum(amount_sold) s_sales, GROUPING(channel_id) gc, GROUPING(promo_id) gp, GROUPING_ID(channel_id, promo_id) gcp, GROUPING_ID(promo_id, channel_id) gpc FROM sales WHERE promo_id > 496 GROUP BY CUBE(channel_id, promo_id); C PROMO_ID S_SALES GC GP GCP GPC - ---------- ---------- ---------- ---------- ---------- ---------- C 497 26094.35 0 0 0 0 C 498 22272.4 0 0 0 0 C 499 19616.8 0 0 0 0 C 9999 87781668 0 0 0 0 C 87849651.6 0 1 1 2 I 497 50325.8 0 0 0 0 I 498 52215.4 0 0 0 0 I 499 58445.85 0 0 0 0 I 9999 169497409 0 0 0 0 I 169658396 0 1 1 2 P 497 31141.75 0 0 0 0 P 498 46942.8 0 0 0 0 P 499 24156 0 0 0 0 P 9999 70890248 0 0 0 0 P 70992488.6 0 1 1 2 S 497 110629.75 0 0 0 0 S 498 82937.25 0 0 0 0 S 499 80999.15 0 0 0 0 S 9999 267205791 0 0 0 0 S 267480357 0 1 1 2 T 497 8319.6 0 0 0 0 T 498 5347.65 0 0 0 0 T 499 19781 0 0 0 0 T 9999 28095689 0 0 0 0 T 28129137.3 0 1 1 2 497 226511.25 1 0 2 1 498 209715.5 1 0 2 1 499 202998.8 1 0 2 1 9999 623470805 1 0 2 1 624110031 1 1 3 3 HEXTORAW Syntax Purpose HEXTORAW converts char containing hexadecimal digits in the CHAR, VARCHAR2, NCHAR, or NVARCHAR2 character set to a raw value. This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion. HEXTORAW ( char )
- 238. INITCAP 5-76 Oracle Database SQL Reference Examples The following example creates a simple table with a raw column, and inserts a hexadecimal value that has been converted to RAW: CREATE TABLE test (raw_col RAW(10)); INSERT INTO test VALUES (HEXTORAW('7D')); INITCAP Syntax Purpose INITCAP returns char, with the first letter of each word in uppercase, all other letters in lowercase. Words are delimited by white space or characters that are not alphanumeric. char can be of any of the datatypes CHAR, VARCHAR2, NCHAR, or NVARCHAR2. The return value is the same datatype as char. The database sets the case of the initial characters based on the binary mapping defined for the underlying character set. For linguistic-sensitive uppercase and lowercase, please refer to NLS_INITCAP on page 5-103. This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion. Examples The following example capitalizes each word in the string: SELECT INITCAP('the soap') "Capitals" FROM DUAL; Capitals --------- The Soap INSERTCHILDXML Syntax See Also: "Datatype Comparison Rules" on page 2-37 for more information. See Also: "RAW and LONG RAW Datatypes" on page 2-23 and RAWTOHEX on page 5-133 See Also: "Datatype Comparison Rules" on page 2-37 for more information. INITCAP ( char ) INSERTCHILDXML ( XMLType_instance , XPath_string , child_expr , value_expr , namespace_string )
- 239. INSERTCHILDXML Functions 5-77 Purpose INSERTCHILDXML inserts a user-supplied value into the target XML at the node indicated by the XPath expression. Compare this function with INSERTXMLBEFORE on page 5-78. ■ XMLType_instance is an instance of XMLType. ■ The XPath_string is an Xpath expression indicating one or more nodes into which the one or more child nodes are to be inserted. You can specify an absolute XPath_string with an initial slash or a relative XPath_string by omitting the initial slash. If you omit the initial slash, the context of the relative path defaults to the root node. ■ The child_expr specifies the one or more element or attribute nodes to be inserted. ■ The value_expr is an fragment of XMLType that specifies one or more notes being inserted. It must resolve to a string. ■ The optional namespace_string provides namespace information for the XPath_string. This parameter must be of type VARCHAR2. Examples The following example adds a second /Owner node to the warehouse_spec of one of the warehouses updated in the example for APPENDCHILDXML on page 5-17: UPDATE warehouses SET warehouse_spec = INSERTCHILDXML(warehouse_spec, '/Warehouse/Building', 'Owner', XMLType('<Owner>LesserCo</Owner>')) WHERE warehouse_id = 3; SELECT warehouse_spec FROM warehouses WHERE warehouse_id = 3; WAREHOUSE_SPEC ---------------------------------------------------------------------------- <?xml version="1.0"?> <Warehouse> <Building>Rented <Owner>Grandco</Owner> <Owner>LesserCo</Owner> </Building> <Area>85700</Area> <DockType/> <WaterAccess>N</WaterAccess> <RailAccess>N</RailAccess> <Parking>Street</Parking> <VClearance>11.5 ft</VClearance> </Warehouse> See Also: Oracle XML DB Developer's Guide for more information about this function
- 240. INSERTXMLBEFORE 5-78 Oracle Database SQL Reference INSERTXMLBEFORE Syntax Purpose INSERTXMLBEFORE inserts a user-supplied value into the target XML before the node indicated by the XPath expression. Compare this function with INSERTCHILDXML on page 5-76. ■ XMLType_instance is an instance of XMLType. ■ The XPath_string is an Xpath expression indicating one or more nodes into which one or more child nodes are to be inserted. You can specify an absolute XPath_string with an initial slash or a relative XPath_string by omitting the initial slash. If you omit the initial slash, the context of the relative path defaults to the root node. ■ The value_expr is a fragment of XMLType that defines one or more nodes being inserted and their position within the parent node. It must resolve to a string. ■ The optional namespace_string provides namespace information for the XPath_string. This parameter must be of type VARCHAR2. Examples The following example is similar to that for INSERTCHILDXML on page 5-76, but it adds a third /Owner node before the /Owner node added in the other example. The output of the query has been formatted for readability. UPDATE warehouses SET warehouse_spec = INSERTXMLBEFORE(warehouse_spec, '/Warehouse/Building/Owner[2]', XMLType('<Owner>ThirdOwner</Owner>')) WHERE warehouse_id = 3; SELECT warehouse_name, EXTRACT(warehouse_spec, '/Warehouse/Building/Owner') "Owners" FROM warehouses WHERE warehouse_id = 3; Name Owners ------------ -------------------------------------------------------------------- New Jersey <Owner>Grandco</Owner> <Owner>ThirdOwner</Owner> <Owner>LesserCo</Owner> See Also: Oracle XML DB Developer's Guide for more information about this function INSERTXMLBEFORE ( XMLType_instance , XPath_string , value_expr , namespace_string )
- 241. INSTR Functions 5-79 INSTR Syntax Purpose The INSTR functions search string for substring. The function returns an integer indicating the position of the character in string that is the first character of this occurrence. INSTR calculates strings using characters as defined by the input character set. INSTRB uses bytes instead of characters. INSTRC uses Unicode complete characters. INSTR2 uses UCS2 code points. INSTR4 uses UCS4 code points. ■ position is an nonzero integer indicating the character of string where Oracle Database begins the search. If position is negative, then Oracle counts backward from the end of string and then searches backward from the resulting position. ■ occurrence is an integer indicating which occurrence of string Oracle should search for. The value of occurrence must be positive. Both string and substring can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The value returned is of NUMBER datatype. Both position and occurrence must be of datatype NUMBER, or any datatype that can be implicitly converted to NUMBER, and must resolve to an integer. The default values of both position and occurrence are 1, meaning Oracle begins searching at the first character of string for the first occurrence of substring. The return value is relative to the beginning of string, regardless of the value of position, and is expressed in characters. If the search is unsuccessful (if substring does not appear occurrence times after the position character of string), then the return value is 0. Examples The following example searches the string CORPORATE FLOOR, beginning with the third character, for the string "OR". It returns the position in CORPORATE FLOOR at which the second occurrence of "OR" begins: SELECT INSTR('CORPORATE FLOOR','OR', 3, 2) "Instring" FROM DUAL; Instring ---------- 14 In the next example, Oracle counts backward from the last character to the third character from the end, which is the first O in FLOOR. Oracle then searches backward for the second occurrence of OR, and finds that this second occurrence begins with the second character in the search string : See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion INSTR INSTRB INSTRC INSTR2 INSTR4 ( string , substring , position , occurrence )
- 242. ITERATION_NUMBER 5-80 Oracle Database SQL Reference SELECT INSTR('CORPORATE FLOOR','OR', -3, 2) "Reversed Instring" FROM DUAL; Reversed Instring ----------------- 2 The next example assumes a double-byte database character set. SELECT INSTRB('CORPORATE FLOOR','OR',5,2) "Instring in bytes" FROM DUAL; Instring in bytes ----------------- 27 ITERATION_NUMBER Syntax Purpose The ITERATION_NUMBER function can be used only in the model_clause of the SELECT statement and then only when ITERATE(number) is specified in the model_ rules_clause. It returns an integer representing the completed iteration through the model rules. The ITERATION_NUMBER function returns 0 during the first iteration. For each subsequent iteration, the ITERATION_NUMBER function returns the equivalent of iteration_number plus one. Examples The following example assigns the sales of the Mouse Pad for the years 1998 and 1999 to the sales of the Mouse Pad for the years 2001 and 2002 respectively: SELECT country, prod, year, s FROM sales_view_ref MODEL PARTITION BY (country) DIMENSION BY (prod, year) MEASURES (sale s) IGNORE NAV UNIQUE DIMENSION RULES UPSERT SEQUENTIAL ORDER ITERATE(2) ( s['Mouse Pad', 2001 + ITERATION_NUMBER] = s['Mouse Pad', 1998 + ITERATION_NUMBER] ) ORDER BY country, prod, year; COUNTRY PROD YEAR S ---------- ----------------------------------- -------- --------- France Mouse Pad 1998 2509.42 France Mouse Pad 1999 3678.69 France Mouse Pad 2000 3000.72 See Also: model_clause on page 19-23 and "Model Expressions" on page 6-11 for the syntax and semantics ITERATION_NUMBER
- 243. LAG Functions 5-81 France Mouse Pad 2001 2509.42 France Mouse Pad 2002 3678.69 France Standard Mouse 1998 2390.83 France Standard Mouse 1999 2280.45 France Standard Mouse 2000 1274.31 France Standard Mouse 2001 2164.54 Germany Mouse Pad 1998 5827.87 Germany Mouse Pad 1999 8346.44 Germany Mouse Pad 2000 7375.46 Germany Mouse Pad 2001 5827.87 Germany Mouse Pad 2002 8346.44 Germany Standard Mouse 1998 7116.11 Germany Standard Mouse 1999 6263.14 Germany Standard Mouse 2000 2637.31 Germany Standard Mouse 2001 6456.13 18 rows selected. The preceding example requires the view sales_view_ref. Please refer to "The MODEL clause: Examples" on page 19-35 to create this view. LAG Syntax Purpose LAG is an analytic function. It provides access to more than one row of a table at the same time without a self join. Given a series of rows returned from a query and a position of the cursor, LAG provides access to a row at a given physical offset prior to that position. If you do not specify offset, then its default is 1. The optional default value is returned if the offset goes beyond the scope of the window. If you do not specify default, then its default is null. You cannot use LAG or any other analytic function for value_expr. That is, you cannot nest analytic functions, but you can use other built-in function expressions for value_expr. Examples The following example provides, for each salesperson in the employees table, the salary of the employee hired just before: See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions, including valid forms of value_ expr See Also: "About SQL Expressions" on page 6-1 for information on valid forms of expr and LEAD on page 5-85 LAG ( value_expr , offset , default ) OVER ( query_partition_clause order_by_clause )
- 244. LAST 5-82 Oracle Database SQL Reference SELECT last_name, hire_date, salary, LAG(salary, 1, 0) OVER (ORDER BY hire_date) AS prev_sal FROM employees WHERE job_id = 'PU_CLERK'; LAST_NAME HIRE_DATE SALARY PREV_SAL ------------------------- --------- ---------- ---------- Khoo 18-MAY-95 3100 0 Tobias 24-JUL-97 2800 3100 Baida 24-DEC-97 2900 2800 Himuro 15-NOV-98 2600 2900 Colmenares 10-AUG-99 2500 2600 LAST Syntax last::= Purpose FIRST and LAST are very similar functions. Both are aggregate and analytic functions that operate on a set of values from a set of rows that rank as the FIRST or LAST with respect to a given sorting specification. If only one row ranks as FIRST or LAST, the aggregate operates on the set with only one element. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument. Please refer to FIRST on page 5-68 for complete information on this function and for examples of its use. See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions of the query_partitioning_ clause See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion aggregate_function KEEP ( DENSE_RANK LAST ORDER BY expr DESC ASC NULLS FIRST LAST , ) OVER query_partition_clause
- 245. LAST_VALUE Functions 5-83 LAST_DAY Syntax Purpose LAST_DAY returns the date of the last day of the month that contains date. The return type is always DATE, regardless of the datatype of date. Examples The following statement determines how many days are left in the current month. SELECT SYSDATE, LAST_DAY(SYSDATE) "Last", LAST_DAY(SYSDATE) - SYSDATE "Days Left" FROM DUAL; SYSDATE Last Days Left --------- --------- ---------- 30-MAY-01 31-MAY-01 1 The following example adds 5 months to the hire date of each employee to give an evaluation date: SELECT last_name, hire_date, TO_CHAR( ADD_MONTHS(LAST_DAY(hire_date), 5)) "Eval Date" FROM employees; LAST_NAME HIRE_DATE Eval Date ------------------------- --------- --------- King 17-JUN-87 30-NOV-87 Kochhar 21-SEP-89 28-FEB-90 De Haan 13-JAN-93 30-JUN-93 Hunold 03-JAN-90 30-JUN-90 Ernst 21-MAY-91 31-OCT-91 Austin 25-JUN-97 30-NOV-97 Pataballa 05-FEB-98 31-JUL-98 Lorentz 07-FEB-99 31-JUL-99 . . . LAST_VALUE Syntax Purpose LAST_VALUE is an analytic function. It returns the last value in an ordered set of values. If the last value in the set is null, then the function returns NULL unless you See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions, including valid forms of expr LAST_DAY ( date ) LAST_VALUE ( expr IGNORE NULLS ) OVER ( analytic_clause )
- 246. LAST_VALUE 5-84 Oracle Database SQL Reference specify IGNORE NULLS. This setting is useful for data densification. If you specify IGNORE NULLS, then LAST_VALUE returns the fist non-null value in the set, or NULL if all values are null. Please refer to "Using Partitioned Outer Joins: Examples" on page 19-41 for an example of data densification. You cannot use LAST_VALUE or any other analytic function for expr. That is, you cannot nest analytic functions, but you can use other built-in function expressions for expr. Please refer to "About SQL Expressions" on page 6-1 for information on valid forms of expr. Examples The following example returns, for each row, the hire date of the employee earning the highest salary: SELECT last_name, salary, hire_date, LAST_VALUE(hire_date) OVER (ORDER BY salary ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS lv FROM (SELECT * FROM employees WHERE department_id = 90 ORDER BY hire_date); LAST_NAME SALARY HIRE_DATE LV ------------------------- ---------- --------- --------- Kochhar 17000 21-SEP-89 17-JUN-87 De Haan 17000 13-JAN-93 17-JUN-87 King 24000 17-JUN-87 17-JUN-87 This example illustrates the nondeterministic nature of the LAST_VALUE function. Kochhar and De Haan have the same salary, so they are in adjacent rows. Kochhar appears first because the rows in the subquery are ordered by hire_date. However, if the rows are ordered by hire_date in descending order, as in the next example, then the function returns a different value: SELECT last_name, salary, hire_date, LAST_VALUE(hire_date) OVER (ORDER BY salary ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS lv FROM (SELECT * FROM employees WHERE department_id = 90 ORDER BY hire_date DESC); LAST_NAME SALARY HIRE_DATE LV ------------------------- ---------- --------- --------- De Haan 17000 13-JAN-93 17-JUN-87 Kochhar 17000 21-SEP-89 17-JUN-87 King 24000 17-JUN-87 17-JUN-87 The following two examples show how to make the LAST_VALUE function deterministic by ordering on a unique key. By ordering within the function by both salary and hire_date, you can ensure the same result regardless of the ordering in the subquery. SELECT last_name, salary, hire_date, LAST_VALUE(hire_date) OVER (ORDER BY salary, hire_date ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS lv FROM (SELECT * FROM employees WHERE department_id = 90 ORDER BY hire_date); LAST_NAME SALARY HIRE_DATE LV ------------------------- ---------- --------- --------- Kochhar 17000 21-SEP-89 17-JUN-87 De Haan 17000 13-JAN-93 17-JUN-87 King 24000 17-JUN-87 17-JUN-87
- 247. LEAD Functions 5-85 SELECT last_name, salary, hire_date, LAST_VALUE(hire_date) OVER (ORDER BY salary, hire_date ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS lv FROM (SELECT * FROM employees WHERE department_id = 90 ORDER BY hire_date DESC); LAST_NAME SALARY HIRE_DATE LV ------------------------- ---------- --------- --------- Kochhar 17000 21-SEP-89 17-JUN-87 De Haan 17000 13-JAN-93 17-JUN-87 King 24000 17-JUN-87 17-JUN-87 LEAD Syntax Purpose LEAD is an analytic function. It provides access to more than one row of a table at the same time without a self join. Given a series of rows returned from a query and a position of the cursor, LEAD provides access to a row at a given physical offset beyond that position. If you do not specify offset, then its default is 1. The optional default value is returned if the offset goes beyond the scope of the table. If you do not specify default, then its default value is null. You cannot use LEAD or any other analytic function for value_expr. That is, you cannot nest analytic functions, but you can use other built-in function expressions for value_expr. Examples The following example provides, for each employee in the employees table, the hire date of the employee hired just after: SELECT last_name, hire_date, LEAD(hire_date, 1) OVER (ORDER BY hire_date) AS "NextHired" FROM employees WHERE department_id = 30; LAST_NAME HIRE_DATE NextHired ------------------------- --------- --------- Raphaely 07-DEC-94 18-MAY-95 Khoo 18-MAY-95 24-JUL-97 See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions, including valid forms of value_ expr See Also: "About SQL Expressions" on page 6-1 for information on valid forms of expr and LAG on page 5-81 LEAD ( value_expr , offset , default ) OVER ( query_partition_clause order_by_clause )
- 248. LEAST 5-86 Oracle Database SQL Reference Tobias 24-JUL-97 24-DEC-97 Baida 24-DEC-97 15-NOV-98 Himuro 15-NOV-98 10-AUG-99 Colmenares 10-AUG-99 LEAST Syntax Purpose LEAST returns the least of the list of exprs. All exprs after the first are implicitly converted to the datatype of the first expr before the comparison. Oracle Database compares the exprs using nonpadded comparison semantics. If the value returned by this function is character data, then its datatype is always VARCHAR2. Examples The following statement selects the string with the least value: SELECT LEAST('HARRY','HARRIOT','HAROLD') "LEAST" FROM DUAL; LEAST ------ HAROLD LENGTH Syntax length::= Purpose The LENGTH functions return the length of char. LENGTH calculates length using characters as defined by the input character set. LENGTHB uses bytes instead of characters. LENGTHC uses Unicode complete characters. LENGTH2 uses UCS2 code points. LENGTH4 uses UCS4 code points. See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion, "Floating-Point Numbers" on page 2-11 for information on binary-float comparison semantics, and "Datatype Comparison Rules" on page 2-37 LEAST ( expr , ) LENGTH LENGTHB LENGTHC LENGTH2 LENGTH4 ( char )
- 249. LN Functions 5-87 char can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The return value is of datatype NUMBER. If char has datatype CHAR, then the length includes all trailing blanks. If char is null, then this function returns null. Restriction on LENGTHB The LENGTHB function is supported for single-byte LOBs only. It cannot be used with CLOB and NCLOB data in a multibyte character set. Examples The following example uses the LENGTH function using a single-byte database character set: SELECT LENGTH('CANDIDE') "Length in characters" FROM DUAL; Length in characters -------------------- 7 The next example assumes a double-byte database character set. SELECT LENGTHB ('CANDIDE') "Length in bytes" FROM DUAL; Length in bytes --------------- 14 LN Syntax Purpose LN returns the natural logarithm of n, where n is greater than 0. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. If the argument is BINARY_ FLOAT, then the function returns BINARY_DOUBLE. Otherwise the function returns the same numeric datatype as the argument. Examples The following example returns the natural logarithm of 95: SELECT LN(95) "Natural log of 95" FROM DUAL; Natural log of 95 ----------------- 4.55387689 See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion LN ( n )
- 250. LNNVL 5-88 Oracle Database SQL Reference LNNVL Syntax Purpose LNNVL provides a concise way to evaluate a condition when one or both operands of the condition may be null. The function can be used only in the WHERE clause of a query. It takes as an argument a condition and returns TRUE if the condition is FALSE or UNKNOWN and FALSE if the condition is TRUE. LNNVL can be used anywhere a scalar expression can appear, even in contexts where the IS [NOT] NULL, AND, or OR conditions are not valid but would otherwise be required to account for potential nulls. Oracle Database sometimes uses the LNNVL function internally in this way to rewrite NOT IN conditions as NOT EXISTS conditions. In such cases, output from EXPLAIN PLAN shows this operation in the plan table output. The condition can evaluate any scalar values but cannot be a compound condition containing AND, OR, or BETWEEN. The table that follows shows what LNNVL returns given that a = 2 and b is null. Examples Suppose that you want to know the number of employees with commission rates of less than 20%, including employees who do not receive commissions. The following query returns only employees who actually receive a commission of less than 20%: SELECT COUNT(*) FROM employees WHERE commission_pct < .2; COUNT(*) ---------- 11 To include the 72 employees who receive no commission at all, you could rewrite the query using the LNNVL function as follows: SELECT COUNT(*) FROM employees WHERE LNNVL(commission_pct >= .2); COUNT(*) ---------- 83 Condition Truth of Condition LNNVL Return Value a = 1 FALSE TRUE a = 2 TRUE FALSE a IS NULL FALSE TRUE b = 1 UNKNOWN TRUE b IS NULL TRUE FALSE a = b UNKNOWN TRUE LNNVL ( condition )
- 251. LOCALTIMESTAMP Functions 5-89 LOCALTIMESTAMP Syntax Purpose LOCALTIMESTAMP returns the current date and time in the session time zone in a value of datatype TIMESTAMP. The difference between this function and CURRENT_ TIMESTAMP is that LOCALTIMESTAMP returns a TIMESTAMP value while CURRENT_ TIMESTAMP returns a TIMESTAMP WITH TIME ZONE value. The optional argument timestamp_precision specifies the fractional second precision of the time value returned. Examples This example illustrates the difference between LOCALTIMESTAMP and CURRENT_ TIMESTAMP: ALTER SESSION SET TIME_ZONE = '-5:00'; SELECT CURRENT_TIMESTAMP, LOCALTIMESTAMP FROM DUAL; CURRENT_TIMESTAMP LOCALTIMESTAMP ------------------------------------------------------------------- 04-APR-00 01.27.18.999220 PM -05:00 04-APR-00 01.27.19 PM ALTER SESSION SET TIME_ZONE = '-8:00'; SELECT CURRENT_TIMESTAMP, LOCALTIMESTAMP FROM DUAL; CURRENT_TIMESTAMP LOCALTIMESTAMP ----------------------------------- ------------------------------ 04-APR-00 10.27.45.132474 AM -08:00 04-APR-00 10.27.451 AM If you use the LOCALTIMESTAMP with a format mask, take care that the format mask matches the value returned by the function. For example, consider the following table: CREATE TABLE local_test (col1 TIMESTAMP WITH LOCAL TIME ZONE); The following statement fails because the mask does not include the TIME ZONE portion of the return type of the function: INSERT INTO local_test VALUES (TO_TIMESTAMP(LOCALTIMESTAMP, 'DD-MON-RR HH.MI.SSXFF')); The following statement uses the correct format mask to match the return type of LOCALTIMESTAMP: INSERT INTO local_test VALUES (TO_TIMESTAMP(LOCALTIMESTAMP, 'DD-MON-RR HH.MI.SSXFF PM')); See Also: CURRENT_TIMESTAMP on page 5-48 LOCALTIMESTAMP ( timestamp_precision )
- 252. LOG 5-90 Oracle Database SQL Reference LOG Syntax Purpose LOG returns the logarithm, base n2, of n1. The base n1 can be any positive value other than 0 or 1 and n2 can be any positive value. This function takes as arguments any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. If any argument is BINARY_ FLOAT or BINARY_DOUBLE, then the function returns BINARY_DOUBLE. Otherwise the function returns NUMBER. Examples The following example returns the log of 100: SELECT LOG(10,100) "Log base 10 of 100" FROM DUAL; Log base 10 of 100 ------------------ 2 LOWER Syntax Purpose LOWER returns char, with all letters lowercase. char can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The return value is the same datatype as char. The database sets the case of the characters based on the binary mapping defined for the underlying character set. For linguistic-sensitive lowercase, please refer to NLS_LOWER on page 5-104. Examples The following example returns a string in lowercase: SELECT LOWER('MR. SCOTT MCMILLAN') "Lowercase" FROM DUAL; Lowercase -------------------- mr. scott mcmillan See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion LOG ( n2 , n1 ) LOWER ( char )
- 253. LTRIM Functions 5-91 LPAD Syntax Purpose LPAD returns expr1, left-padded to length n characters with the sequence of characters in expr2. This function is useful for formatting the output of a query. Both expr1 and expr2 can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The string returned is of VARCHAR2 datatype if expr1 is a character datatype and a LOB if expr1 is a LOB datatype. The string returned is in the same character set as expr1. The argument n must be a NUMBER integer or a value that can be implicitly converted to a NUMBER integer. If you do not specify expr2, then the default is a single blank. If expr1 is longer than n, then this function returns the portion of expr1 that fits in n. The argument n is the total length of the return value as it is displayed on your terminal screen. In most character sets, this is also the number of characters in the return value. However, in some multibyte character sets, the display length of a character string can differ from the number of characters in the string. Examples The following example left-pads a string with the asterisk (*) and period (.) characters: SELECT LPAD('Page 1',15,'*.') "LPAD example" FROM DUAL; LPAD example --------------- *.*.*.*.*Page 1 LTRIM Syntax Purpose LTRIM removes from the left end of char all of the characters contained in set. If you do not specify set, it defaults to a single blank. If char is a character literal, then you must enclose it in single quotes. Oracle Database begins scanning char from its first character and removes all characters that appear in set until reaching a character not in set and then returns the result. Both char and set can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The string returned is of VARCHAR2 datatype if char is a character datatype and a LOB if char is a LOB datatype. See Also: RTRIM on page 5-153 LPAD ( expr1 , n , expr2 ) LTRIM ( char , set )
- 254. MAKE_REF 5-92 Oracle Database SQL Reference Examples The following example trims the redundant first word from a group of product names in the oe.products table: SELECT product_name, LTRIM(product_name, ’Monitor ’) "Short Name" FROM products WHERE product_name LIKE ’Monitor%’; PRODUCT_NAME Short Name -------------------- --------------- Monitor 17/HR 17/HR Monitor 17/HR/F 17/HR/F Monitor 17/SD 17/SD Monitor 19/SD 19/SD Monitor 19/SD/M 19/SD/M Monitor 21/D 21/D Monitor 21/HR 21/HR Monitor 21/HR/M 21/HR/M Monitor 21/SD 21/SD Monitor Hinge - HD Hinge - HD Monitor Hinge - STD Hinge - STD MAKE_REF Syntax Purpose MAKE_REF creates a REF to a row of an object view or a row in an object table whose object identifier is primary key based. This function is useful, for example, if you are creating an object view Examples The sample schema oe contains an object view oc_inventories based on inventory_typ. The object identifier is product_id. The following example creates a REF to the row in the oc_inventories object view with a product_id of 3003: SELECT MAKE_REF (oc_inventories, 3003) FROM DUAL; MAKE_REF(OC_INVENTORIES,3003) ------------------------------------------------------------------ 00004A038A0046857C14617141109EE03408002082543600000014260100010001 00290090606002A00078401FE0000000B03C21F040000000000000000000000000 0000000000 See Also: Oracle Database Application Developer's Guide - Object-Relational Features for more information about object views and DEREF on page 5-56 MAKE_REF ( table view , key , )
- 255. MAX Functions 5-93 MAX Syntax Purpose MAX returns maximum value of expr. You can use it as an aggregate or analytic function. Aggregate Example The following example determines the highest salary in the hr.employees table: SELECT MAX(salary) "Maximum" FROM employees; Maximum ---------- 24000 Analytic Example The following example calculates, for each employee, the highest salary of the employees reporting to the same manager as the employee. SELECT manager_id, last_name, salary, MAX(salary) OVER (PARTITION BY manager_id) AS mgr_max FROM employees; MANAGER_ID LAST_NAME SALARY MGR_MAX ---------- ------------------------- ---------- ---------- 100 Kochhar 17000 17000 100 De Haan 17000 17000 100 Raphaely 11000 17000 100 Kaufling 7900 17000 100 Fripp 8200 17000 100 Weiss 8000 17000 . . . If you enclose this query in the parent query with a predicate, then you can determine the employee who makes the highest salary in each department: SELECT manager_id, last_name, salary FROM (SELECT manager_id, last_name, salary, MAX(salary) OVER (PARTITION BY manager_id) AS rmax_sal FROM employees) WHERE salary = rmax_sal; MANAGER_ID LAST_NAME SALARY ---------- ------------------------- ---------- See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: "About SQL Expressions" on page 6-1 for information on valid forms of expr, "Floating-Point Numbers" on page 2-11 for information on binary-float comparison semantics, and "Aggregate Functions" on page 5-8 MAX ( DISTINCT ALL expr ) OVER ( analytic_clause )
- 256. MEDIAN 5-94 Oracle Database SQL Reference 100 Kochhar 17000 100 De Haan 17000 101 Greenberg 12000 101 Higgens 12000 102 Hunold 9000 103 Ernst 6000 108 Faviet 9000 114 Khoo 3100 120 Nayer 3200 120 Taylor 3200 121 Sarchand 4200 122 Chung 3800 123 Bell 4000 124 Rajs 3500 145 Tucker 10000 146 King 10000 147 Vishney 10500 148 Ozer 11500 149 Abel 11000 201 Goyal 6000 205 Gietz 8300 King 24000 MEDIAN Syntax Purpose MEDIAN is an inverse distribution function that assumes a continuous distribution model. It takes a numeric or datetime value and returns the middle value or an interpolated value that would be the middle value once the values are sorted. Nulls are ignored in the calculation. This function takes as arguments any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. If you specify only expr, then the function returns the same datatype as the numeric datatype of the argument. if you specify the OVER clause, then Oracle Database determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype, and returns that datatype. The result of MEDIAN is computed by first ordering the rows. Using N as the number of rows in the group, Oracle calculates the row number (RN) of interest with the formula RN = (1 + (0.5*(N-1)). The final result of the aggregate function is computed by linear interpolation between the values from rows at row numbers CRN = CEILING(RN) and FRN = FLOOR(RN). See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion and "Numeric Precedence" on page 2-13 for information on numeric precedence MEDIAN ( expr ) OVER ( query_partition_clause )
- 257. MEDIAN Functions 5-95 The final result will be: if (CRN = FRN = RN) then (value of expression from row at RN) else (CRN - RN) * (value of expression for row at FRN) + (RN - FRN) * (value of expression for row at CRN) You can use MEDIAN as an analytic function. You can specify only the query_ partition_clause in its OVER clause. It returns, for each row, the value that would fall in the middle among a set of values within each partition. Compare this function with these functions: ■ PERCENTILE_CONT on page 5-114, which returns, for a given percentile, the value that corresponds to that percentile by way of interpolation. MEDIAN is the specific case of PERCENTILE_CONT where the percentile value defaults to 0.5. ■ PERCENTILE_DISC on page 5-116, which is useful for finding values for a given percentile without interpolation. Aggregate Example The following query returns the median salary for each department in the hr.employees table: SELECT department_id, MEDIAN(salary) FROM employees GROUP BY department_id; DEPARTMENT_ID MEDIAN(SALARY) ------------- -------------- 10 4400 20 9500 30 2850 40 6500 50 3100 60 4800 70 10000 80 8900 90 17000 100 8000 110 10150 7000 Analytic Example The following query returns the median salary for each manager in a subset of departments in the hr.employees table: SELECT manager_id, employee_id, salary, MEDIAN(salary) OVER (PARTITION BY manager_id) "Median by Mgr" FROM employees WHERE department_id > 60; MANAGER_ID EMPLOYEE_ID SALARY Median by Mgr ---------- ----------- ---------- ------------- 100 149 10500 13500 100 148 11000 13500 100 147 12000 13500 100 146 13500 13500 100 145 14000 13500
- 258. MIN 5-96 Oracle Database SQL Reference 100 101 17000 13500 100 102 17000 13500 101 204 10000 12000 101 108 12000 12000 101 205 12000 12000 108 113 6900 7800 108 111 7700 7800 108 112 7800 7800 108 110 8200 7800 108 109 9000 7800 145 155 7000 8500 145 154 7500 8500 . . . MIN Syntax Purpose MIN returns minimum value of expr. You can use it as an aggregate or analytic function. Aggregate Example The following statement returns the earliest hire date in the hr.employees table: SELECT MIN(hire_date) "Earliest" FROM employees; Earliest --------- 17-JUN-87 Analytic Example The following example determines, for each employee, the employees who were hired on or before the same date as the employee. It then determines the subset of employees reporting to the same manager as the employee, and returns the lowest salary in that subset. SELECT manager_id, last_name, hire_date, salary, MIN(salary) OVER(PARTITION BY manager_id ORDER BY hire_date RANGE UNBOUNDED PRECEDING) AS p_cmin FROM employees; MANAGER_ID LAST_NAME HIRE_DATE SALARY P_CMIN See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: "About SQL Expressions" on page 6-1 for information on valid forms of expr, "Floating-Point Numbers" on page 2-11 for information on binary-float comparison semantics, and "Aggregate Functions" on page 5-8 MIN ( DISTINCT ALL expr ) OVER ( analytic_clause )
- 259. MOD Functions 5-97 ---------- ------------------------- --------- ---------- ---------- 100 Kochhar 21-SEP-89 17000 17000 100 De Haan 13-JAN-93 17000 17000 100 Raphaely 07-DEC-94 11000 11000 100 Kaufling 01-MAY-95 7900 7900 100 Hartstein 17-FEB-96 13000 7900 100 Weiss 18-JUL-96 8000 7900 100 Russell 01-OCT-96 14000 7900 100 Partners 05-JAN-97 13500 7900 100 Errazuriz 10-MAR-97 12000 7900 . . . MOD Syntax Purpose MOD returns the remainder of n2 divided by n1. Returns n2 if n1 is 0. This function takes as arguments any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. Oracle determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype, and returns that datatype. Examples The following example returns the remainder of 11 divided by 4: SELECT MOD(11,4) "Modulus" FROM DUAL; Modulus ---------- 3 This function behaves differently from the classical mathematical modulus function when m is negative. The classical modulus can be expressed using the MOD function with this formula: m - n * FLOOR(m/n) The following table illustrates the difference between the MOD function and the classical modulus: See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion and "Numeric Precedence" on page 2-13 for information on numeric precedence m n MOD(m,n) Classical Modulus 11 4 3 3 11 -4 3 -1 -11 4 -3 1 -11 -4 -3 -3 MOD ( n2 , n1 )
- 260. MONTHS_BETWEEN 5-98 Oracle Database SQL Reference MONTHS_BETWEEN Syntax Purpose MONTHS_BETWEEN returns number of months between dates date1 and date2. If date1 is later than date2, then the result is positive. If date1 is earlier than date2, then the result is negative. If date1 and date2 are either the same days of the month or both last days of months, then the result is always an integer. Otherwise Oracle Database calculates the fractional portion of the result based on a 31-day month and considers the difference in time components date1 and date2. Examples The following example calculates the months between two dates: SELECT MONTHS_BETWEEN (TO_DATE('02-02-1995','MM-DD-YYYY'), TO_DATE('01-01-1995','MM-DD-YYYY') ) "Months" FROM DUAL; Months ---------- 1.03225806 NANVL Syntax Purpose The NANVL function is useful only for floating-point numbers of type BINARY_FLOAT or BINARY_DOUBLE. It instructs Oracle Database to return an alternative value n1 if the input value n2 is NaN (not a number). If n2 is not NaN, then Oracle returns n2. This function is useful for mapping NaN values to NULL. This function takes as arguments any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. Oracle determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype, and returns that datatype. See Also: FLOOR on page 5-71 and REMAINDER on page 5-147, which is similar to MOD, but uses ROUND in its formula instead of FLOOR See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion, "Floating-Point Numbers" on page 2-11 for information on binary-float comparison semantics, and "Numeric Precedence" on page 2-13 for information on numeric precedence MONTHS_BETWEEN ( date1 , date2 ) NANVL ( n2 , n1 )
- 261. NCHR Functions 5-99 Examples Using table float_point_demo created for TO_BINARY_DOUBLE on page 5-188, insert a second entry into the table: Insert INTO float_point_demo VALUES (0,'NaN','NaN'); SELECT * FROM float_point_demo; DEC_NUM BIN_DOUBLE BIN_FLOAT ---------- ---------- ---------- 1234.56 1.235E+003 1.235E+003 0 Nan Nan The following example returns bin_float if it is a number. Otherwise, 0 is returned. SELECT bin_float, NANVL(bin_float,0) FROM float_point_demo; BIN_FLOAT NANVL(BIN_FLOAT,0) ---------- ------------------ 1.235E+003 1.235E+003 Nan 0 NCHR Syntax Purpose NCHR returns the character having the binary equivalent to number in the national character set. The value returned is always NVARCHAR2. This function is equivalent to using the CHR function with the USING NCHAR_CS clause. This function takes as an argument a NUMBER value, or any value that can be implicitly converted to NUMBER, and returns a character. Examples The following examples return the nchar character 187: SELECT NCHR(187) FROM DUAL; NC -- > SELECT CHR(187 USING NCHAR_CS) FROM DUAL; CH -- > See Also: CHR on page 5-28 NCHR ( number )
- 262. NEW_TIME 5-100 Oracle Database SQL Reference NEW_TIME Syntax Purpose NEW_TIME returns the date and time in time zone timezone2 when date and time in time zone timezone1 are date. Before using this function, you must set the NLS_ DATE_FORMAT parameter to display 24-hour time. The return type is always DATE, regardless of the datatype of date. The arguments timezone1 and timezone2 can be any of these text strings: ■ AST, ADT: Atlantic Standard or Daylight Time ■ BST, BDT: Bering Standard or Daylight Time ■ CST, CDT: Central Standard or Daylight Time ■ EST, EDT: Eastern Standard or Daylight Time ■ GMT: Greenwich Mean Time ■ HST, HDT: Alaska-Hawaii Standard Time or Daylight Time. ■ MST, MDT: Mountain Standard or Daylight Time ■ NST: Newfoundland Standard Time ■ PST, PDT: Pacific Standard or Daylight Time ■ YST, YDT: Yukon Standard or Daylight Time Examples The following example returns an Atlantic Standard time, given the Pacific Standard time equivalent: ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS'; SELECT NEW_TIME(TO_DATE( '11-10-99 01:23:45', 'MM-DD-YY HH24:MI:SS'), 'AST', 'PST') "New Date and Time" FROM DUAL; New Date and Time -------------------- 09-NOV-1999 21:23:45 Note: This function takes as input only a limited number of time zones. You can have access to a much greater number of time zones by combining the FROM_TZ function and the datetime expression. See FROM_TZ on page 5-71 and the example for "Datetime Expressions" on page 6-8. NEW_TIME ( date , timezone1 , timezone2 )
- 263. NLS_CHARSET_DECL_LEN Functions 5-101 NEXT_DAY Syntax Purpose NEXT_DAY returns the date of the first weekday named by char that is later than the date date. The return type is always DATE, regardless of the datatype of date. The argument char must be a day of the week in the date language of your session, either the full name or the abbreviation. The minimum number of letters required is the number of letters in the abbreviated version. Any characters immediately following the valid abbreviation are ignored. The return value has the same hours, minutes, and seconds component as the argument date. Examples This example returns the date of the next Tuesday after February 2, 2001: SELECT NEXT_DAY('02-FEB-2001','TUESDAY') "NEXT DAY" FROM DUAL; NEXT DAY ----------- 06-FEB-2001 NLS_CHARSET_DECL_LEN Syntax Purpose NLS_CHARSET_DECL_LEN returns the declaration length (in number of characters) of an NCHAR column. The byte_count argument is the width of the column. The char_ set_id argument is the character set ID of the column. Examples The following example returns the number of characters that are in a 200-byte column when you are using a multibyte character set: SELECT NLS_CHARSET_DECL_LEN (200, nls_charset_id('ja16eucfixed')) FROM DUAL; NLS_CHARSET_DECL_LEN(200,NLS_CHARSET_ID('JA16EUCFIXED')) -------------------------------------------------------- 100 NEXT_DAY ( date , char ) NLS_CHARSET_DECL_LEN ( byte_count , ’ char_set_id ’ )
- 264. NLS_CHARSET_ID 5-102 Oracle Database SQL Reference NLS_CHARSET_ID Syntax Purpose NLS_CHARSET_ID returns the character set ID number corresponding to character set name string. The string argument is a run-time VARCHAR2 value. The string value 'CHAR_CS' returns the database character set ID number of the server. The string value 'NCHAR_CS' returns the national character set ID number of the server. Invalid character set names return null. Examples The following example returns the character set ID of a character set: SELECT NLS_CHARSET_ID('ja16euc') FROM DUAL; NLS_CHARSET_ID('JA16EUC') ------------------------- 830 NLS_CHARSET_NAME Syntax Purpose NLS_CHARSET_NAME returns the name of the character set corresponding to ID number number. The character set name is returned as a VARCHAR2 value in the database character set. If number is not recognized as a valid character set ID, then this function returns null. Examples The following example returns the character set corresponding to character set ID number 2: SELECT NLS_CHARSET_NAME(2) FROM DUAL; NLS_CH ------ WE8DEC See Also: Oracle Database Globalization Support Guide for a list of character set names See Also: Oracle Database Globalization Support Guide for a list of character set IDs NLS_CHARSET_ID ( string ) NLS_CHARSET_NAME ( number )
- 265. NLS_INITCAP Functions 5-103 NLS_INITCAP Syntax Purpose NLS_INITCAP returns char, with the first letter of each word in uppercase, all other letters in lowercase. Words are delimited by white space or characters that are not alphanumeric. Both char and 'nlsparam' can be any of the datatypes CHAR, VARCHAR2, NCHAR, or NVARCHAR2. The string returned is of VARCHAR2 datatype and is in the same character set as char. The value of 'nlsparam' can have this form: 'NLS_SORT = sort' where sort is either a linguistic sort sequence or BINARY. The linguistic sort sequence handles special linguistic requirements for case conversions. These requirements can result in a return value of a different length than the char. If you omit 'nlsparam', then this function uses the default sort sequence for your session. This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion. Examples The following examples show how the linguistic sort sequence results in a different return value from the function: SELECT NLS_INITCAP ('ijsland') "InitCap" FROM DUAL; InitCap ------- Ijsland SELECT NLS_INITCAP ('ijsland', 'NLS_SORT = XDutch') "InitCap" FROM DUAL; InitCap ------- IJsland See Also: "Datatype Comparison Rules" on page 2-37 for more information. See Also: Oracle Database Globalization Support Guide for information on sort sequences NLS_INITCAP ( char , ’ nlsparam ’ )
- 266. NLS_LOWER 5-104 Oracle Database SQL Reference NLS_LOWER Syntax Purpose NLS_LOWER returns char, with all letters lowercase. Both char and 'nlsparam' can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The string returned is of VARCHAR2 datatype if char is a character datatype and a LOB if char is a LOB datatype. The return string is in the same character set as char. The 'nlsparam' can have the same form and serve the same purpose as in the NLS_ INITCAP function. Examples The following statement returns the character string 'citta'' using the XGerman linguistic sort sequence: SELECT NLS_LOWER ('CITTA''', 'NLS_SORT = XGerman') "Lowercase" FROM DUAL; Lowerc ------ citta' NLSSORT Syntax Purpose NLSSORT returns the string of bytes used to sort char. Both char and 'nlsparam' can be any of the datatypes CHAR, VARCHAR2, NCHAR, or NVARCHAR2. The string returned is of RAW datatype. The value of 'nlsparam' can have the form 'NLS_SORT = sort' where sort is a linguistic sort sequence or BINARY. If you omit 'nlsparam', then this function uses the default sort sequence for your session. If you specify BINARY, then this function returns char. If you specify 'nlsparam', then you can append to the linguistic sort name the suffix _ai to request an accent-insensitive sort or _ci to request a case-insensitive sort. Please refer to Oracle Database Globalization Support Guide for more information on accent- and case-insensitive sorting. NLS_LOWER ( char , ’ nlsparam ’ ) NLSSORT ( char , ’ nlsparam ’ )
- 267. NLSSORT Functions 5-105 This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion. Examples This function can be used to specify sorting and comparison operations based on a linguistic sort sequence rather than on the binary value of a string. The following example creates a test table containing two values and shows how the values returned can be ordered by the NLSSORT function: CREATE TABLE test (name VARCHAR2(15)); INSERT INTO test VALUES ('Gaardiner'); INSERT INTO test VALUES ('Gaberd'); INSERT INTO test VALUES ('Gaasten'); SELECT * FROM test ORDER BY name; NAME --------------- Gaardiner Gaasten Gaberd SELECT * FROM test ORDER BY NLSSORT(name, 'NLS_SORT = XDanish'); NAME --------------- Gaberd Gaardiner Gaasten The following example shows how to use the NLSSORT function in comparison operations: SELECT * FROM test WHERE name > 'Gaberd'; no rows selected SELECT * FROM test WHERE NLSSORT(name, 'NLS_SORT = XDanish') > NLSSORT('Gaberd', 'NLS_SORT = XDanish'); NAME --------------- Gaardiner Gaasten If you frequently use NLSSORT in comparison operations with the same linguistic sort sequence, then consider this more efficient alternative: Set the NLS_COMP parameter (either for the database or for the current session) to LINGUISTIC, and set the NLS_ SORT parameter for the session to the desired sort sequence. Oracle Database will use that sort sequence by default for all sorting and comparison operations during the current session: ALTER SESSION SET NLS_COMP = 'LINGUISTIC'; ALTER SESSION SET NLS_SORT = 'XDanish'; SELECT * FROM test WHERE name > 'Gaberd'; See Also: "Datatype Comparison Rules" on page 2-37 for more information.
- 268. NLS_UPPER 5-106 Oracle Database SQL Reference NAME --------------- Gaardiner Gaasten NLS_UPPER Syntax Purpose NLS_UPPER returns char, with all letters uppercase. Both char and 'nlsparam' can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The string returned is of VARCHAR2 datatype if char is a character datatype and a LOB if char is a LOB datatype. The return string is in the same character set as char. The 'nlsparam' can have the same form and serve the same purpose as in the NLS_ INITCAP function. Examples The following example returns a string with all the letters converted to uppercase: SELECT NLS_UPPER ('große') "Uppercase" FROM DUAL; Upper ----- GROßE SELECT NLS_UPPER ('große', 'NLS_SORT = XGerman') "Uppercase" FROM DUAL; Upperc ------ GROSSE NTILE Syntax See Also: Oracle Database Globalization Support Guide for information on sort sequences See Also: NLS_INITCAP on page 5-103 See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions, including valid forms of expr NLS_UPPER ( char , ’ nlsparam ’ ) NTILE ( expr ) OVER ( query_partition_clause order_by_clause )
- 269. NULLIF Functions 5-107 Purpose NTILE is an analytic function. It divides an ordered data set into a number of buckets indicated by expr and assigns the appropriate bucket number to each row. The buckets are numbered 1 through expr. The expr value must resolve to a positive constant for each partition. Oracle Database expects an integer, and if expr is a noninteger constant, then Oracle truncates the value to an integer. The return value is NUMBER. The number of rows in the buckets can differ by at most 1. The remainder values (the remainder of number of rows divided by buckets) are distributed one for each bucket, starting with bucket 1. If expr is greater than the number of rows, then a number of buckets equal to the number of rows will be filled, and the remaining buckets will be empty. You cannot use NTILE or any other analytic function for expr. That is, you cannot nest analytic functions, but you can use other built-in function expressions for expr. Examples The following example divides into 4 buckets the values in the salary column of the oe.employees table from Department 100. The salary column has 6 values in this department, so the two extra values (the remainder of 6 / 4) are allocated to buckets 1 and 2, which therefore have one more value than buckets 3 or 4. SELECT last_name, salary, NTILE(4) OVER (ORDER BY salary DESC) AS quartile FROM employees WHERE department_id = 100; LAST_NAME SALARY QUARTILE ------------------------- ---------- ---------- Greenberg 12000 1 Faviet 9000 1 Chen 8200 2 Urman 7800 2 Sciarra 7700 3 Popp 6900 4 NULLIF Syntax Purpose NULLIF compares expr1 and expr2. If they are equal, then the function returns null. If they are not equal, then the function returns expr1. You cannot specify the literal NULL for expr1. If both arguments are numeric datatypes, then Oracle Database determines the argument with the higher numeric precedence, implicitly converts the other argument to that datatype, and returns that datatype. If the arguments are not numeric, then they must be of the same datatype, or Oracle returns an error. See Also: "About SQL Expressions" on page 6-1 for information on valid forms of expr and Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion NULLIF ( expr1 , expr2 )
- 270. NUMTODSINTERVAL 5-108 Oracle Database SQL Reference The NULLIF function is logically equivalent to the following CASE expression: CASE WHEN expr1 = expr 2 THEN NULL ELSE expr1 END Examples The following example selects those employees from the sample schema hr who have changed jobs since they were hired, as indicated by a job_id in the job_history table different from the current job_id in the employees table: SELECT e.last_name, NULLIF(e.job_id, j.job_id) "Old Job ID" FROM employees e, job_history j WHERE e.employee_id = j.employee_id ORDER BY last_name; LAST_NAME Old Job ID ------------------------- ---------- De Haan AD_VP Hartstein MK_MAN Kaufling ST_MAN Kochhar AD_VP Kochhar AD_VP Raphaely PU_MAN Taylor SA_REP Taylor Whalen AD_ASST Whalen NUMTODSINTERVAL Syntax Purpose NUMTODSINTERVAL converts n to an INTERVAL DAY TO SECOND literal. The argument n can be any NUMBER value or an expression that can be implicitly converted to a NUMBER value. The argument interval_unit can be of CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype. The value for interval_unit specifies the unit of n and must resolve to one of the following string values: ■ 'DAY' ■ 'HOUR' ■ 'MINUTE' ■ 'SECOND' interval_unit is case insensitive. Leading and trailing values within the parentheses are ignored. By default, the precision of the return is 9. See Also: "CASE Expressions" on page 6-5 See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion NUMTODSINTERVAL ( n , ’ interval_unit ’ )
- 271. NUMTOYMINTERVAL Functions 5-109 Examples The following example uses NUMTODSINTERVAL in a COUNT analytic function to calculate, for each employee, the number of employees hired by the same manager within the past 100 days from his or her hire date. Please refer to "Analytic Functions" on page 5-9 for more information on the syntax of the analytic functions. SELECT manager_id, last_name, hire_date, COUNT(*) OVER (PARTITION BY manager_id ORDER BY hire_date RANGE NUMTODSINTERVAL(100, 'day') PRECEDING) AS t_count FROM employees; MANAGER_ID LAST_NAME HIRE_DATE T_COUNT ---------- ------------------------- --------- ---------- 100 Kochhar 21-SEP-89 1 100 De Haan 13-JAN-93 1 100 Raphaely 07-DEC-94 1 100 Kaufling 01-MAY-95 1 100 Hartstein 17-FEB-96 1 . . . 149 Grant 24-MAY-99 1 149 Johnson 04-JAN-00 1 201 Goyal 17-AUG-97 1 205 Gietz 07-JUN-94 1 King 17-JUN-87 1 NUMTOYMINTERVAL Syntax Purpose NUMTOYMINTERVAL converts number n to an INTERVAL YEAR TO MONTH literal. The argument n can be any NUMBER value or an expression that can be implicitly converted to a NUMBER value. The argument interval_unit can be of CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype. The value for interval_unit specifies the unit of n and must resolve to one of the following string values: ■ 'YEAR' ■ 'MONTH' interval_unit is case insensitive. Leading and trailing values within the parentheses are ignored. By default, the precision of the return is 9. Examples The following example uses NUMTOYMINTERVAL in a SUM analytic function to calculate, for each employee, the total salary of employees hired in the past one year from his or her hire date. Please refer to "Analytic Functions" on page 5-9 for more information on the syntax of the analytic functions. SELECT last_name, hire_date, salary, SUM(salary) OVER (ORDER BY hire_date RANGE NUMTOYMINTERVAL(1,'year') PRECEDING) AS t_sal See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion NUMTOYMINTERVAL ( n , ’ interval_unit ’ )
- 272. NVL 5-110 Oracle Database SQL Reference FROM employees; LAST_NAME HIRE_DATE SALARY T_SAL ------------------------- --------- ---------- ---------- King 17-JUN-87 24000 24000 Whalen 17-SEP-87 4400 28400 Kochhar 21-SEP-89 17000 17000 . . . Markle 08-MAR-00 2200 112400 Ande 24-MAR-00 6400 106500 Banda 21-APR-00 6200 109400 Kumar 21-APR-00 6100 109400 NVL Syntax Purpose NVL lets you replace null (returned as a blank) with a string in the results of a query. If expr1 is null, then NVL returns expr2. If expr1 is not null, then NVL returns expr1. The arguments expr1 and expr2 can have any datatype. If their datatypes are different, then Oracle Database implicitly converts one to the other. If they are cannot be converted implicitly, the database returns an error. The implicit conversion is implemented as follows: ■ If expr1 is character data, then Oracle Database converts expr2 to the datatype of expr1 before comparing them and returns VARCHAR2 in the character set of expr1. ■ If expr1 is numeric, then Oracle determines which argument has the highest numeric precedence, implicitly converts the other argument to that datatype, and returns that datatype. Examples The following example returns a list of employee names and commissions, substituting "Not Applicable" if the employee receives no commission: SELECT last_name, NVL(TO_CHAR(commission_pct), 'Not Applicable') "COMMISSION" FROM employees WHERE last_name LIKE 'B%' ORDER BY last_name; LAST_NAME COMMISSION ------------------------- ---------------------------------------- Baer Not Applicable Baida Not Applicable Banda .1 Bates .15 Bell Not Applicable Bernstein .25 See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion and "Numeric Precedence" on page 2-13 for information on numeric precedence NVL ( expr1 , expr2 )
- 273. NVL2 Functions 5-111 Bissot Not Applicable Bloom .2 Bull Not Applicable NVL2 Syntax Purpose NVL2 lets you determine the value returned by a query based on whether a specified expression is null or not null. If expr1 is not null, then NVL2 returns expr2. If expr1 is null, then NVL2 returns expr3. The argument expr1 can have any datatype. The arguments expr2 and expr3 can have any datatypes except LONG. If the datatypes of expr2 and expr3 are different: ■ If expr2 is character data, then Oracle Database converts expr3 to the datatype of expr2 before comparing them unless expr3 is a null constant. In that case, a datatype conversion is not necessary. Oracle returns VARCHAR2 in the character set of expr2. ■ If expr2 is numeric, then Oracle determines which argument has the highest numeric precedence, implicitly converts the other argument to that datatype, and returns that datatype. Examples The following example shows whether the income of some employees is made up of salary plus commission, or just salary, depending on whether the commission_pct column of employees is null or not. SELECT last_name, salary, NVL2(commission_pct, salary + (salary * commission_pct), salary) income FROM employees WHERE last_name like 'B%' ORDER BY last_name; LAST_NAME SALARY INCOME ------------------------- ---------- ---------- Baer 10000 10000 Baida 2900 2900 Banda 6200 6882 Bates 7300 8468 Bell 4000 4000 Bernstein 9500 11970 Bissot 3300 3300 Bloom 10000 12100 Bull 4100 4100 See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion and "Numeric Precedence" on page 2-13 for information on numeric precedence NVL2 ( expr1 , expr2 , expr3 )
- 274. ORA_HASH 5-112 Oracle Database SQL Reference ORA_HASH Syntax Purpose ORA_HASH is a function that computes a hash value for a given expression. This function is useful for operations such as analyzing a subset of data and generating a random sample. ■ The expr argument determines the data for which you want Oracle Database to compute a hash value. There are no restrictions on the type or length of data represented by expr, which commonly resolves to a column name. ■ The optional max_bucket argument determines the maximum bucket value returned by the hash function. You can specify any value between 0 and 4294967295. The default is 4294967295. ■ The optional seed_value argument enables Oracle to produce many different results for the same set of data. Oracle applies the hash function to the combination of expr and seed_value. You can specify any value between 0 and 4294967295. The default is 0. The function returns a NUMBER value. Examples The following example creates a hash value for each combination of customer ID and product ID in the sh.sales table, divides the hash values into a maximum of 100 buckets, and returns the sum of the amount_sold values in the first bucket (bucket 0). The third argument (5) provides a seed value for the hash function. You can obtain different hash results for the same query by changing the seed value. SELECT SUM(amount_sold) FROM sales WHERE ORA_HASH(CONCAT(cust_id, prod_id), 99, 5) = 0; SUM(AMOUNT_SOLD) ---------------- 989431.14 PATH Syntax Purpose PATH is an ancillary function used only with the UNDER_PATH and EQUALS_PATH conditions. It returns the relative path that leads to the resource specified in the parent condition. ORA_HASH ( expr , max_bucket , seed_value ) PATH ( correlation_integer )
- 275. PERCENT_RANK Functions 5-113 The correlation_integer can be any NUMBER integer and is used to correlate this ancillary function with its primary condition. Values less than 1 are treated as 1. Example Please refer to the related function DEPTH on page 5-55 for an example using both of these ancillary functions of the EQUALS_PATH and UNDER_PATH conditions. PERCENT_RANK Aggregate Syntax percent_rank_aggregate::= Analytic Syntax percent_rank_analytic::= Purpose PERCENT_RANK is similar to the CUME_DIST (cumulative distribution) function. The range of values returned by PERCENT_RANK is 0 to 1, inclusive. The first row in any set has a PERCENT_RANK of 0. The return value is NUMBER. ■ As an aggregate function, PERCENT_RANK calculates, for a hypothetical row r identified by the arguments of the function and a corresponding sort specification, the rank of row r minus 1 divided by the number of rows in the aggregate group. This calculation is made as if the hypothetical row r were inserted into the group of rows over which Oracle Database is to aggregate. The arguments of the function identify a single hypothetical row within each aggregate group. Therefore, they must all evaluate to constant expressions within each aggregate group. The constant argument expressions and the expressions in the ORDER BY clause of the See Also: EQUALS_PATH Condition on page 7-19 and UNDER_ PATH Condition on page 7-20 See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion PERCENT_RANK ( expr , ) WITHIN GROUP ( ORDER BY expr DESC ASC NULLS FIRST LAST , ) PERCENT_RANK ( ) OVER ( query_partition_clause order_by_clause )
- 276. PERCENTILE_CONT 5-114 Oracle Database SQL Reference aggregate match by position. Therefore the number of arguments must be the same and their types must be compatible. ■ As an analytic function, for a row r, PERCENT_RANK calculates the rank of r minus 1, divided by 1 less than the number of rows being evaluated (the entire query result set or a partition). Aggregate Example The following example calculates the percent rank of a hypothetical employee in the sample table hr.employees with a salary of $15,500 and a commission of 5%: SELECT PERCENT_RANK(15000, .05) WITHIN GROUP (ORDER BY salary, commission_pct) "Percent-Rank" FROM employees; Percent-Rank ------------ .971962617 Analytic Example The following example calculates, for each employee, the percent rank of the employee's salary within the department: SELECT department_id, last_name, salary, PERCENT_RANK() OVER (PARTITION BY department_id ORDER BY salary DESC) AS pr FROM employees ORDER BY pr, salary; DEPARTMENT_ID LAST_NAME SALARY PR ------------- ------------------------- ---------- ---------- 10 Whalen 4400 0 40 Marvis 6500 0 . . . 80 Vishney 10500 .176470588 50 Everett 3900 .181818182 30 Khoo 3100 .2 . . . 80 Johnson 6200 .941176471 50 Markle 2200 .954545455 50 Philtanker 2200 .954545455 50 Olson 2100 1 . . . PERCENTILE_CONT Syntax PERCENTILE_CONT ( expr ) WITHIN GROUP ( ORDER BY expr DESC ASC ) OVER ( query_partition_clause )
- 277. PERCENTILE_CONT Functions 5-115 Purpose PERCENTILE_CONT is an inverse distribution function that assumes a continuous distribution model. It takes a percentile value and a sort specification, and returns an interpolated value that would fall into that percentile value with respect to the sort specification. Nulls are ignored in the calculation. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument. The first expr must evaluate to a numeric value between 0 and 1, because it is a percentile value. This expr must be constant within each aggregation group. The ORDER BY clause takes a single expression that must be a numeric or datetime value, as these are the types over which Oracle can perform interpolation. The result of PERCENTILE_CONT is computed by linear interpolation between values after ordering them. Using the percentile value (P) and the number of rows (N) in the aggregation group, we compute the row number we are interested in after ordering the rows with respect to the sort specification. This row number (RN) is computed according to the formula RN = (1+ (P*(N-1)). The final result of the aggregate function is computed by linear interpolation between the values from rows at row numbers CRN = CEILING(RN) and FRN = FLOOR(RN). The final result will be: If (CRN = FRN = RN) then the result is (value of expression from row at RN) Otherwise the result is (CRN - RN) * (value of expression for row at FRN) + (RN - FRN) * (value of expression for row at CRN) You can use the PERCENTILE_CONT function as an analytic function. You can specify only the query_partitioning_clause in its OVER clause. It returns, for each row, the value that would fall into the specified percentile among a set of values within each partition. The MEDIAN function is a specific case of PERCENTILE_CONT where the percentile value defaults to 0.5. For more information, please refer to MEDIAN on page 5-94. Aggregate Example The following example computes the median salary in each department: SELECT department_id, PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY salary DESC) "Median cont", PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY salary DESC) "Median disc" FROM employees GROUP BY department_id; DEPARTMENT_ID Median-cont Median-disc ------------- ----------- ----------- 10 4400 4400 20 9500 13000 See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions of the OVER clause See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion
- 278. PERCENTILE_DISC 5-116 Oracle Database SQL Reference 30 2850 2900 40 6500 6500 50 3100 3100 60 4800 4800 70 10000 10000 80 8800 8800 90 17000 17000 100 8000 8200 110 10150 12000 PERCENTILE_CONT and PERCENTILE_DISC may return different results. PERCENTILE_CONT returns a computed result after doing linear interpolation. PERCENTILE_DISC simply returns a value from the set of values that are aggregated over. When the percentile value is 0.5, as in this example, PERCENTILE_CONT returns the average of the two middle values for groups with even number of elements, whereas PERCENTILE_DISC returns the value of the first one among the two middle values. For aggregate groups with an odd number of elements, both functions return the value of the middle element. Analytic Example In the following example, the median for Department 60 is 4800, which has a corresponding percentile (Percent_Rank) of 0.5. None of the salaries in Department 30 have a percentile of 0.5, so the median value must be interpolated between 2900 (percentile 0.4) and 2800 (percentile 0.6), which evaluates to 2850. SELECT last_name, salary, department_id, PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY salary DESC) OVER (PARTITION BY department_id) "Percentile_Cont", PERCENT_RANK() OVER (PARTITION BY department_id ORDER BY salary DESC) "Percent_Rank" FROM employees WHERE department_id IN (30, 60); LAST_NAME SALARY DEPARTMENT_ID Percentile_Cont Percent_Rank ------------- ---------- ------------- --------------- ------------ Raphaely 11000 30 2850 0 Khoo 3100 30 2850 .2 Baida 2900 30 2850 .4 Tobias 2800 30 2850 .6 Himuro 2600 30 2850 .8 Colmenares 2500 30 2850 1 Hunold 9000 60 4800 0 Ernst 6000 60 4800 .25 Austin 4800 60 4800 .5 Pataballa 4800 60 4800 .5 Lorentz 4200 60 4800 1 PERCENTILE_DISC Syntax PERCENTILE_DISC ( expr ) WITHIN GROUP ( ORDER BY expr DESC ASC ) OVER ( query_partition_clause )
- 279. PERCENTILE_DISC Functions 5-117 Purpose PERCENTILE_DISC is an inverse distribution function that assumes a discrete distribution model. It takes a percentile value and a sort specification and returns an element from the set. Nulls are ignored in the calculation. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument. The first expr must evaluate to a numeric value between 0 and 1, because it is a percentile value. This expression must be constant within each aggregate group. The ORDER BY clause takes a single expression that can be of any type that can be sorted. For a given percentile value P, PERCENTILE_DISC sorts the values of the expression in the ORDER BY clause and returns the value with the smallest CUME_DIST value (with respect to the same sort specification) that is greater than or equal to P. Aggregate Example See aggregate example for PERCENTILE_CONT on page 5-114. Analytic Example The following example calculates the median discrete percentile of the salary of each employee in the sample table hr.employees: SELECT last_name, salary, department_id, PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY salary DESC) OVER (PARTITION BY department_id) "Percentile_Disc", CUME_DIST() OVER (PARTITION BY department_id ORDER BY salary DESC) "Cume_Dist" FROM employees where department_id in (30, 60); LAST_NAME SALARY DEPARTMENT_ID Percentile_Disc Cume_Dist ------------- ---------- ------------- --------------- ---------- Raphaely 11000 30 2900 .166666667 Khoo 3100 30 2900 .333333333 Baida 2900 30 2900 .5 Tobias 2800 30 2900 .666666667 Himuro 2600 30 2900 .833333333 Colmenares 2500 30 2900 1 Hunold 9000 60 4800 .2 Ernst 6000 60 4800 .4 Austin 4800 60 4800 .8 Pataballa 4800 60 4800 .8 Lorentz 4200 60 4800 1 The median value for Department 30 is 2900, which is the value whose corresponding percentile (Cume_Dist) is the smallest value greater than or equal to 0.5. The median value for Department 60 is 4800, which is the value whose corresponding percentile is the smallest value greater than or equal to 0.5. See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions of the OVER clause See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion
- 280. POWER 5-118 Oracle Database SQL Reference POWER Syntax Purpose POWER returns n2 raised to the n1 power. The base n2 and the exponent n1 can be any numbers, but if n2 is negative, then n1 must be an integer. This function takes as arguments any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. If any argument is BINARY_ FLOAT or BINARY_DOUBLE, then the function returns BINARY_DOUBLE. Otherwise the function returns NUMBER. Examples The following example returns 3 squared: SELECT POWER(3,2) "Raised" FROM DUAL; Raised ---------- 9 POWERMULTISET Syntax Purpose POWERMULTISET takes as input a nested table and returns a nested table of nested tables containing all nonempty subsets (called submultisets) of the input nested table. ■ expr can be any expression that evaluates to a nested table. ■ If expr resolves to null, then Oracle Database returns NULL. ■ If expr resolves to a nested table that is empty, then Oracle returns an error. ■ The element types of the nested table must be comparable. Please refer to "Comparison Conditions" on page 7-4 for information on the comparability of nonscalar types. Examples First, create a datatype that is a nested table of the cust_address_tab_type datatype: CREATE TYPE cust_address_tab_tab_typ AS TABLE OF cust_address_tab_typ; See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion Note: This function is not supported in PL/SQL. POWER ( n2 , n1 ) POWERMULTISET ( expr )
- 281. POWERMULTISET_BY_CARDINALITY Functions 5-119 Now, select the nested table column cust_address_ntab from the customers_ demo table using the POWERMULTISET function: SELECT CAST(POWERMULTISET(cust_address_ntab) AS cust_address_tab_tab_typ) FROM customers_demo; CAST(POWERMULTISET(CUST_ADDRESS_NTAB) AS CUST_ADDRESS_TAB_TAB_TYP) (STREET_ADDRESS, POSTAL_CODE, CITY, STATE_PROVINCE, COUNTRY_ID) ------------------------------------------------------------------ CUST_ADDRESS_TAB_TAB_TYP(CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP ('514 W Superior St', '46901', 'Kokomo', 'IN', 'US'))) CUST_ADDRESS_TAB_TAB_TYP(CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP ('2515 Bloyd Ave', '46218', 'Indianapolis', 'IN', 'US'))) CUST_ADDRESS_TAB_TAB_TYP(CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP ('8768 N State Rd 37', '47404', 'Bloomington', 'IN', 'US'))) CUST_ADDRESS_TAB_TAB_TYP(CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP ('6445 Bay Harbor Ln', '46254', 'Indianapolis', 'IN', 'US'))) . . . The preceding example requires the customers_demo table and a nested table column containing data. Please refer to "Multiset Operators" on page 4-5 to create this table and nested table columns. POWERMULTISET_BY_CARDINALITY Syntax Purpose POWERMULTISET_BY_CARDINALITY takes as input a nested table and a cardinality and returns a nested table of nested tables containing all nonempty subsets (called submultisets) of the nested table of the specified cardinality. ■ expr can be any expression that evaluates to a nested table. ■ cardinality can be any positive integer. ■ If expr resolves to null, Oracle Database returns NULL. ■ If expr resolves to a nested table that is empty, then Oracle returns an error. ■ The element types of the nested table must be comparable. Please refer to "Comparison Conditions" on page 7-4 for information on the comparability of nonscalar types. Examples First, duplicate the elements in all the nested table rows to increase the cardinality of the nested table rows to 2: UPDATE customers_demo SET cust_address_ntab = cust_address_ntab MULTISET UNION cust_address_ntab; Note: This function is not supported in PL/SQL. POWERMULTISET_BY_CARDINALITY ( expr , cardinality )
- 282. PREDICTION 5-120 Oracle Database SQL Reference Now, select the nested table column cust_address_ntab from the customers_ demo table using the POWERMULTISET_BY_CARDINALITY function: SELECT CAST(POWERMULTISET_BY_CARDINALITY(cust_address_ntab, 2) AS cust_address_tab_tab_typ) FROM customers_demo; CAST(POWERMULTISET_BY_CARDINALITY(CUST_ADDRESS_NTAB,2) AS CUST_ADDRESS_TAB_TAB_TYP) (STREET_ADDRESS, POSTAL_CODE, CITY, STATE_PROVINCE, COUNTRY_ID) ---------------------------------------------------------------------------------------- CUST_ADDRESS_TAB_TAB_TYP(CUST_ADDRESS_TAB_TYP (CUST_ADDRESS_TYP('514 W Superior St', '46901', 'Kokomo', 'IN', 'US'), CUST_ADDRESS_TYP('514 W Superior St', '46901', 'Kokomo', 'IN', 'US'))) CUST_ADDRESS_TAB_TAB_TYP(CUST_ADDRESS_TAB_TYP (CUST_ADDRESS_TYP('2515 Bloyd Ave', '46218', 'Indianapolis', 'IN', 'US'), CUST_ADDRESS_TYP('2515 Bloyd Ave', '46218', 'Indianapolis', 'IN', 'US'))) CUST_ADDRESS_TAB_TAB_TYP(CUST_ADDRESS_TAB_TYP (CUST_ADDRESS_TYP('8768 N State Rd 37', '47404', 'Bloomington', 'IN', 'US'), CUST_ADDRESS_TYP('8768 N State Rd 37', '47404', 'Bloomington', 'IN', 'US'))) . . . The preceding example requires the customers_demo table and a nested table column containing data. Please refer to "Multiset Operators" on page 4-5 to create this table and nested table columns. PREDICTION Syntax cost_matrix_clause::= mining_attribute_clause::= Purpose This function is for use with models created by the DBMS_DATA_MINING package or with the Oracle Data Mining Java API. It returns the best prediction for the model. The datatype returned depends on the target value type used during the build of the model. For regression models, this function returns the expected value. COST MODEL Specify COST MODEL to indicate that the scoring should be performed by taking into account the cost matrix that was associated with the model at build PREDICTION ( schema . model cost_matrix_clause mining_attribute_clause ) COST MODEL USING * schema . table . * expr AS alias ,
- 283. PREDICTION Functions 5-121 time. If no such cost matrix exists, then the database returns an error. The COST MODEL clause is relevant only for decision tree classification models. If you omit the COST MODEL clause, the best prediction is the target class with the highest probability. If two or more classes are tied with the highest probability, the database chooses one class. mining_attribute_clause This maps the predictors that were provided when the model was built. Specifying USING * maps to all to the columns and expressions that can be retrieved from the underlying inputs (tables, views, and so on). ■ If you specify more predictors in the mining_attribute_clause than there are predictors used by the model, then the extra expressions are silently ignored. ■ If you specify fewer predictors than are used during the build, then the operation proceeds with the subset of predictors you specify and returns information on a best-effort basis. All types of models will return a result regardless of the number of predictors you specify in this clause. ■ If you specify a predictor with the same name as was used during the build but a different datatype, then the database implicitly converts to produce a predictor value of the same type as the original build. Example The following example returns by gender the average age of customers who are likely to use an affinity card. The PREDICTION function takes into account only the cust_ marital_status, education, and household_size predictors. This example, and the prerequisite data mining operations, including the creation of the view, can be found in the demo file $ORACLE_ HOME/rdbms/demo/dmdtdemo.sql. General information on data mining demo files is available in Oracle Data Mining Administrator's Guide. The example is presented here to illustrate the syntactic use of the function. SELECT cust_gender, COUNT(*) AS cnt, ROUND(AVG(age)) AS avg_age FROM mining_data_apply_v WHERE PREDICTION(DT_SH_Clas_sample COST MODEL USING cust_marital_status, education, household_size) = 1 GROUP BY cust_gender ORDER BY cust_gender; C CNT AVG_AGE - ---------- ---------- F 170 38 M 685 42 See Also: ■ Oracle Data Mining Concepts for detailed information on Oracle Data Mining features ■ Oracle Data Mining Administrator's Guide for information on the demo programs available in the code ■ Oracle Data Mining Application Developer's Guide for information on writing Oracle Data Mining applications
- 284. PREDICTION_COST 5-122 Oracle Database SQL Reference PREDICTION_COST Syntax cost_matrix_clause::= mining_attribute_clause::= Purpose This function is for use with decision tree classification models created by the DBMS_ DATA_MINING package or with the Oracle Data Mining Java API. It is not valid with other types of models. It returns a measure of cost for a given prediction as an Oracle NUMBER. If you specify the optional class parameter, then the function returns the cost for the specified class. If you omit the class parameter, then the function returns the cost associated with the best prediction. You can use this form in conjunction with the PREDICTION function to obtain the best pair of prediction value and cost. COST MODEL indicates that the scoring should be performed by taking into account the cost matrix that was associated with the model at build time. If no such cost matrix exists, then the database returns an error. The mining_attribute_clause behaves as described for the PREDICTION function. Please refer to mining_attribute_clause on page 5-121. Example The following example finds the ten customers living in Italy who are least expensive to convince to use an affinity card. This example and the prerequisite data mining operations can be found in the demo file $ORACLE_HOME/rdbms/demo/dmdtdemo.sql. General information on data See Also: ■ Oracle Data Mining Concepts for detailed information on Oracle Data Mining features ■ Oracle Data Mining Administrator's Guide for information on the demo programs available in the code ■ Oracle Data Mining Application Developer's Guide for information on writing Oracle Data Mining applications PREDICTION_COST ( schema . model , class cost_matrix_clause mining_attribute_clause ) COST MODEL USING * schema . table . * expr AS alias ,
- 285. PREDICTION_DETAILS Functions 5-123 mining demo files is available in Oracle Data Mining Administrator's Guide. The example is presented here to illustrate the syntactic use of the function. WITH cust_italy AS ( SELECT cust_id FROM mining_data_apply_v WHERE country_name = 'Italy' ORDER BY PREDICTION_COST(DT_SH_Clas_sample, 1 COST MODEL USING *) ASC, 1 ) SELECT cust_id FROM cust_italy WHERE rownum < 11; CUST_ID ---------- 100081 100179 100185 100324 100344 100554 100662 100733 101250 101306 10 rows selected. PREDICTION_DETAILS Syntax mining_attribute_clause::= Purpose This function is for use with decision tree models and single-feature Adaptive Bayes Network (ABN) models created by the DBMS_DATA_MINING package or with the Oracle Data Mining Java API. It returns an XML string containing model-specific information related to the scoring of the input row. In this release, the return value takes the following form: <Node id= "integer"/> PREDICTION_DETAILS ( schema . model mining_attribute_clause ) USING * schema . table . * expr AS alias ,
- 286. PREDICTION_PROBABILITY 5-124 Oracle Database SQL Reference where integer is the identifier of a data mining tree node. The form of the output is subject to change. It may be enhanced to provide additional prediction information in future releases. The mining_attribute_clause behaves as described for the PREDICTION function. Please refer to mining_attribute_clause on page 5-121. Example The following example uses all attributes from the mining_data_apply_v view that are relevant predictors for the DT_SH_Clas_sample decision tree model. For customers who work in technical support and are under age 25, it returns the tree node that results from scoring those records with the DT_SH_Clas_sample model. This example, and the prerequisite data mining operations, including the creation of the view, can be found in the demo files $ORACLE_ HOME/rdbms/demo/dmdtdemo.sql. General information on data mining demo files is available in Oracle Data Mining Administrator's Guide. The example is presented here to illustrate the syntactic use of the function. SELECT cust_id, education, PREDICTION_DETAILS(DT_SH_Clas_sample using *) treenode FROM mining_data_apply_v WHERE occupation = ’TechSup’ AND age < 25 ORDER BY cust_id; CUST_ID EDUCATION TREENODE ---------- --------------------- ------------------------- 100234 < Bach. <Node id="21"/> 100320 < Bach. <Node id="21"/> 100349 < Bach. <Node id="21"/> 100419 < Bach. <Node id="21"/> 100583 < Bach. <Node id="13"/> 100657 HS-grad <Node id="21"/> 101171 < Bach. <Node id="21"/> 101225 < Bach. <Node id="21"/> 101338 < Bach. <Node id="21"/> 9 rows selected. PREDICTION_PROBABILITY Syntax See Also: ■ Oracle Data Mining Concepts for detailed information on Oracle Data Mining features ■ Oracle Data Mining Administrator's Guide for information on the demo programs available in the code ■ Oracle Data Mining Application Developer's Guide for information on writing Oracle Data Mining applications PREDICTION_PROBABILITY ( schema . model , class mining_attribute_clause )
- 287. PREDICTION_PROBABILITY Functions 5-125 mining_attribute_clause::= Purpose This function is for use with classification models created by the DBMS_DATA_MINING package or with the Oracle Data Mining Java API. It is not valid with other types of models. It returns the probability for a given prediction as an Oracle NUMBER. If you specify the optional class parameter, then the function returns the probability for the specified class. This is equivalent to the probability associated with choosing the given target class value. If you omit the class parameter, then the function returns the probability associated with the best prediction. You can use this form in conjunction with the PREDICTION function to obtain the best pair of prediction value and probability. The mining_attribute_clause behaves as described for the PREDICTION function. Please refer to mining_attribute_clause on page 5-121. Example The following example returns the 10 customers living in Italy who are most likely to use an affinity card. This example, and the prerequisite data mining operations, including the creation of the view, can be found in the demo files $ORACLE_ HOME/rdbms/demo/dmdtdemo.sql. General information on data mining demo files is available in Oracle Data Mining Administrator's Guide. The example is presented here to illustrate the syntactic use of the function. SELECT cust_id FROM ( SELECT cust_id FROM mining_data_apply_v WHERE country_name = 'Italy' ORDER BY PREDICTION_PROBABILITY(DT_SH_Clas_sample, 1 USING *) DESC, cust_id) WHERE rownum < 11; CUST_ID ---------- 100081 100179 See Also: ■ Oracle Data Mining Concepts for detailed information on Oracle Data Mining features ■ Oracle Data Mining Administrator's Guide for information on the demo programs available in the code ■ Oracle Data Mining Application Developer's Guide for information on writing Oracle Data Mining applications USING * schema . table . * expr AS alias ,
- 288. PREDICTION_SET 5-126 Oracle Database SQL Reference 100185 100324 100344 100554 100662 100733 101250 101306 10 rows selected. PREDICTION_SET Syntax cost_matrix_clause::= mining_attribute_clause::= Purpose This function is for use with classification models created using the DBMS_DATA_ MINING package or with the Oracle Data Mining Java API. It is not valid with other types of models. It returns a varray of objects containing all classes in a multiclass classification scenario. The object fields are named PREDICTION, PROBABILITY, and COST. The datatype of the PREDICTION field depends on the target value type used during the build of the model. The other two fields are both Oracle NUMBER. The elements are returned in the order of best prediction to worst prediction. ■ For bestN, specify a positive integer to restrict the returned target classes to the N having the highest probability. If multiple classes are tied in the Nth value, the database still returns only N values. If you want to filter only by cutoff, specify NULL for this parameter. ■ For cutoff, specify a NUMBER value to restrict the returned target classes to those with a cost less than or equal to the specified cost value. You can filter solely by cutoff by specifying NULL for bestN. PREDICTION_SET ( schema . model , bestN , cutoff cost_matrix_clause mining_attribute_clause ) COST MODEL USING * schema . table . * expr AS alias ,
- 289. PREDICTION_SET Functions 5-127 When you specify values for both bestN and cutoff, you restrict the returned predictions to only those that are the bestN and have a probability (or cost when COST MODEL is specified) surpassing the threshold. ■ Specify COST MODEL to indicate that the scoring should be performed by taking into account the cost matrix that was associated with the model at build time. If no such cost matrix exists, then the database returns an error. When you specify COST MODEL, both bestN and cutoff are treated with respect to the prediction cost, not the prediction probability. That is, bestN restricts the result to the target classes having the N best (lowest) costs, and cutoff restricts the target classes to those with a cost less than or equal to the specified cutoff. When you specify this clause, each object in the collection is a triplet of scalar values containing the prediction value (the datatype of which depends on the target value type used during model build), the prediction probability, and the prediction cost (both Oracle NUMBER). If you omit COST MODEL, each object in the varray is a pair of scalars containing the prediction value and prediction probability. The datatypes returned are as described in the preceding paragraph. The mining_attribute_clause behaves as described for the PREDICTION function. Please refer to mining_attribute_clause on page 5-121. Example The following example lists, for ten customers, the likelihood and cost of using or rejecting an affinity card. This example has a binary target, but such a query is also useful in multiclass classification such as Low, Med, and High. This example and the prerequisite data mining operations can be found in the demo file $ORACLE_HOME/rdbms/demo/dmdtdemo.sql. General information on data mining demo files is available in Oracle Data Mining Administrator's Guide. The example is presented here to illustrate the syntactic use of the function. SELECT T.cust_id, S.prediction, S.probability, S.cost FROM (SELECT cust_id, PREDICTION_SET(dt_sh_clas_sample COST MODEL USING *) pset FROM mining_data_apply_v WHERE cust_id < 100011) T, TABLE(T.pset) S ORDER BY cust_id, S.prediction; CUST_ID PREDICTION PROBABILITY COST ---------- ---------- ----------- ----- 100001 0 .96682 .27 100001 1 .03318 .97 100002 0 .74038 2.08 100002 1 .25962 .74 100003 0 .90909 .73 See Also: ■ Oracle Data Mining Concepts for detailed information on Oracle Data Mining features ■ Oracle Data Mining Administrator's Guide for information on the demo programs available in the code ■ Oracle Data Mining Application Developer's Guide for information on writing Oracle Data Mining applications
- 290. PRESENTNNV 5-128 Oracle Database SQL Reference 100003 1 .09091 .91 100004 0 .90909 .73 100004 1 .09091 .91 100005 0 .27236 5.82 100005 1 .72764 .27 100006 0 1.00000 .00 100006 1 .00000 1.00 100007 0 .90909 .73 100007 1 .09091 .91 100008 0 .90909 .73 100008 1 .09091 .91 100009 0 .27236 5.82 100009 1 .72764 .27 100010 0 .80808 1.54 100010 1 .19192 .81 20 rows selected. PRESENTNNV Syntax Purpose The PRESENTNNV function can be used only in the model_clause of the SELECT statement and then only on the right-hand side of a model rule. It returns expr1 when, prior to the execution of the model_clause, cell_reference exists and is not null. Otherwise it returns expr2. Examples In the following example, if a row containing sales for the Mouse Pad for the year 2002 exists, and the sales value is not null, then the sales value remains unchanged. If the row exists and the sales value is null, then the sales value is set to 10. If the row does not exist, then the row is created with the sales value set to 10. SELECT country, prod, year, s FROM sales_view_ref MODEL PARTITION BY (country) DIMENSION BY (prod, year) MEASURES (sale s) IGNORE NAV UNIQUE DIMENSION RULES UPSERT SEQUENTIAL ORDER ( s['Mouse Pad', 2002] = PRESENTNNV(s['Mouse Pad', 2002], s['Mouse Pad', 2002], 10) ) ORDER BY country, prod, year; COUNTRY PROD YEAR S ---------- ----------------------------------- -------- --------- France Mouse Pad 1998 2509.42 France Mouse Pad 1999 3678.69 See Also: model_clause on page 19-23 and "Model Expressions" on page 6-11 for the syntax and semantics PRESENTNNV ( cell_reference , expr1 , expr2 )
- 291. PRESENTV Functions 5-129 France Mouse Pad 2000 3000.72 France Mouse Pad 2001 3269.09 France Mouse Pad 2002 10 France Standard Mouse 1998 2390.83 France Standard Mouse 1999 2280.45 France Standard Mouse 2000 1274.31 France Standard Mouse 2001 2164.54 Germany Mouse Pad 1998 5827.87 Germany Mouse Pad 1999 8346.44 Germany Mouse Pad 2000 7375.46 Germany Mouse Pad 2001 9535.08 Germany Mouse Pad 2002 10 Germany Standard Mouse 1998 7116.11 Germany Standard Mouse 1999 6263.14 Germany Standard Mouse 2000 2637.31 Germany Standard Mouse 2001 6456.13 18 rows selected. The preceding example requires the view sales_view_ref. Please refer to "Examples" on page 19-30 to create this view. PRESENTV Syntax Purpose The PRESENTV function can be used only within the model_clause of the SELECT statement and then only on the right-hand side of a model rule. It returns expr1 when, prior to the execution of the model_clause, cell_reference exists. Otherwise it returns expr2. Examples In the following example, if a row containing sales for the Mouse Pad for the year 2000 exists, then the sales value for the Mouse Pad for the year 2001 is set to the sales value for the Mouse Pad for the year 2000. If the row does not exist, then a row is created with the sales value for the Mouse Pad for year 20001 set to 0. SELECT country, prod, year, s FROM sales_view_ref MODEL PARTITION BY (country) DIMENSION BY (prod, year) MEASURES (sale s) IGNORE NAV UNIQUE DIMENSION RULES UPSERT SEQUENTIAL ORDER ( s['Mouse Pad', 2001] = PRESENTV(s['Mouse Pad', 2000], s['Mouse Pad', 2000], 0) ) See Also: model_clause on page 19-23 and "Model Expressions" on page 6-11 for the syntax and semantics PRESENTV ( cell_reference , expr1 , expr2 )
- 292. PREVIOUS 5-130 Oracle Database SQL Reference ORDER BY country, prod, year; COUNTRY PROD YEAR S ---------- ----------------------------------- -------- --------- France Mouse Pad 1998 2509.42 France Mouse Pad 1999 3678.69 France Mouse Pad 2000 3000.72 France Mouse Pad 2001 3000.72 France Standard Mouse 1998 2390.83 France Standard Mouse 1999 2280.45 France Standard Mouse 2000 1274.31 France Standard Mouse 2001 2164.54 Germany Mouse Pad 1998 5827.87 Germany Mouse Pad 1999 8346.44 Germany Mouse Pad 2000 7375.46 Germany Mouse Pad 2001 7375.46 Germany Standard Mouse 1998 7116.11 Germany Standard Mouse 1999 6263.14 Germany Standard Mouse 2000 2637.31 Germany Standard Mouse 2001 6456.13 16 rows selected. The preceding example requires the view sales_view_ref. Please refer to "The MODEL clause: Examples" on page 19-35 to create this view. PREVIOUS Syntax Purpose The PREVIOUS function can be used only in the model_clause of the SELECT statement and then only in the ITERATE ... [ UNTIL ] clause of the model_rules_ clause. It returns the value of cell_reference at the beginning of each iteration. Examples The following example repeats the rules, up to 1000 times, until the difference between the values of cur_val at the beginning and at the end of an iteration is less than one: SELECT dim_col, cur_val, num_of_iterations FROM (SELECT 1 AS dim_col, 10 AS cur_val FROM dual) MODEL DIMENSION BY (dim_col) MEASURES (cur_val, 0 num_of_iterations) IGNORE NAV UNIQUE DIMENSION RULES ITERATE (1000) UNTIL (PREVIOUS(cur_val[1]) - cur_val[1] < 1) ( cur_val[1] = cur_val[1]/2, num_of_iterations[1] = num_of_iterations[1] + 1 ); See Also: model_clause on page 19-23 and "Model Expressions" on page 6-11 for the syntax and semantics PREVIOUS ( cell_reference )
- 293. RANK Functions 5-131 DIM_COL CUR_VAL NUM_OF_ITERATIONS ---------- ---------- ----------------- 1 .625 4 RANK Aggregate Syntax rank_aggregate::= Analytic Syntax rank_analytic::= Purpose RANK calculates the rank of a value in a group of values. The return type is NUMBER. Rows with equal values for the ranking criteria receive the same rank. Oracle Database then adds the number of tied rows to the tied rank to calculate the next rank. Therefore, the ranks may not be consecutive numbers. This function is useful for top-N and bottom-N reporting. ■ As an aggregate function, RANK calculates the rank of a hypothetical row identified by the arguments of the function with respect to a given sort specification. The arguments of the function must all evaluate to constant expressions within each aggregate group, because they identify a single row within each group. The constant argument expressions and the expressions in the ORDER BY clause of the aggregate match by position. Therefore, the number of arguments must be the same and their types must be compatible. ■ As an analytic function, RANK computes the rank of each row returned from a query with respect to the other rows returned by the query, based on the values of the value_exprs in the order_by_clause. See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion and "Numeric Precedence" on page 2-13 for information on numeric precedence RANK ( expr , ) WITHIN GROUP ( ORDER BY expr DESC ASC NULLS FIRST LAST , ) RANK ( ) OVER ( query_partition_clause order_by_clause )
- 294. RANK 5-132 Oracle Database SQL Reference Aggregate Example The following example calculates the rank of a hypothetical employee in the sample table hr.employees with a salary of $15,500 and a commission of 5%: SELECT RANK(15500, .05) WITHIN GROUP (ORDER BY salary, commission_pct) "Rank" FROM employees; Rank ---------- 105 Similarly, the following query returns the rank for a $15,500 salary among the employee salaries: SELECT RANK(15500) WITHIN GROUP (ORDER BY salary DESC) "Rank of 15500" FROM employees; Rank of 15500 -------------- 4 Analytic Example The following statement ranks the employees in the sample hr schema in department 80 based on their salary and commission. Identical salary values receive the same rank and cause nonconsecutive ranks. Compare this example with the example for DENSE_ RANK on page 5-54. SELECT department_id, last_name, salary, commission_pct, RANK() OVER (PARTITION BY department_id ORDER BY salary DESC, commission_pct) "Rank" FROM employees WHERE department_id = 80; DEPARTMENT_ID LAST_NAME SALARY COMMISSION_PCT Rank ------------- ------------------------- ---------- -------------- ---------- 80 Russell 14000 .4 1 80 Partners 13500 .3 2 80 Errazuriz 12000 .3 3 80 Ozer 11500 .25 4 80 Cambrault 11000 .3 5 80 Abel 11000 .3 5 80 Zlotkey 10500 .2 7 80 Vishney 10500 .25 8 80 Bloom 10000 .2 9 80 Tucker 10000 .3 10 80 King 10000 .35 11 80 Fox 9600 .2 12 80 Greene 9500 .15 13 80 Bernstein 9500 .25 14 80 Sully 9500 .35 15 80 Hall 9000 .25 16 80 McEwen 9000 .35 17 80 Hutton 8800 .25 18 80 Taylor 8600 .2 19 80 Livingston 8400 .2 20 80 Olsen 8000 .2 21 80 Smith 8000 .3 22 80 Cambrault 7500 .2 23 80 Doran 7500 .3 24
- 295. RAWTOHEX Functions 5-133 80 Smith 7400 .15 25 80 Bates 7300 .15 26 80 Marvins 7200 .1 27 80 Tuvault 7000 .15 28 80 Sewall 7000 .25 29 80 Lee 6800 .1 30 80 Ande 6400 .1 31 80 Banda 6200 .1 32 80 Johnson 6200 .1 32 80 Kumar 6100 .1 34 RATIO_TO_REPORT Syntax Purpose RATIO_TO_REPORT is an analytic function. It computes the ratio of a value to the sum of a set of values. If expr evaluates to null, then the ratio-to-report value also evaluates to null. The set of values is determined by the query_partition_clause. If you omit that clause, then the ratio-to-report is computed over all rows returned by the query. You cannot use RATIO_TO_REPORT or any other analytic function for expr. That is, you cannot nest analytic functions, but you can use other built-in function expressions for expr. Please refer to "About SQL Expressions" on page 6-1 for information on valid forms of expr. Examples The following example calculates the ratio-to-report value of each purchasing clerk's salary to the total of all purchasing clerks' salaries: SELECT last_name, salary, RATIO_TO_REPORT(salary) OVER () AS rr FROM employees WHERE job_id = 'PU_CLERK'; LAST_NAME SALARY RR ------------------------- ---------- ---------- Khoo 3100 .223021583 Baida 2900 .208633094 Tobias 2800 .201438849 Himuro 2600 .18705036 Colmenares 2500 .179856115 RAWTOHEX Syntax See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions, including valid forms of expr RATIO_TO_REPORT ( expr ) OVER ( query_partition_clause ) RAWTOHEX ( raw )
- 296. RAWTONHEX 5-134 Oracle Database SQL Reference Purpose RAWTOHEX converts raw to a character value containing its hexadecimal equivalent. The raw argument must be RAW datatype. You can specify a BLOB argument for this function if it is called from within a PL/SQL block. Examples The following hypothetical example returns the hexadecimal equivalent of a RAW column value: SELECT RAWTOHEX(raw_column) "Graphics" FROM graphics; Graphics -------- 7D RAWTONHEX Syntax Purpose RAWTONHEX converts raw to an NVARCHAR2 character value containing its hexadecimal equivalent. The value returned is always in the national character set. Examples The following hypothetical example returns the hexadecimal equivalent of a RAW column value: SELECT RAWTONHEX(raw_column), DUMP ( RAWTONHEX (raw_column) ) "DUMP" FROM graphics; RAWTONHEX(RA) DUMP ----------------------- ------------------------------ 7D Typ=1 Len=4: 0,55,0,68 REF Syntax Purpose REF takes as its argument a correlation variable (table alias) associated with a row of an object table or an object view. A REF value is returned for the object instance that is bound to the variable or row. See Also: "RAW and LONG RAW Datatypes" on page 2-23 and HEXTORAW on page 5-75 RAWTONHEX ( raw ) REF ( correlation_variable )
- 297. REFTOHEX Functions 5-135 Examples The sample schema oe contains a type called cust_address_typ, described as follows: Attribute Type ----------------------------- ---------------- STREET_ADDRESS VARCHAR2(40) POSTAL_CODE VARCHAR2(10) CITY VARCHAR2(30) STATE_PROVINCE VARCHAR2(10) COUNTRY_ID CHAR(2) The following example creates a table based on the sample type oe.cust_address_ typ, inserts a row into the table, and retrieves a REF value for the object instance of the type in the addresses table: CREATE TABLE addresses OF cust_address_typ; INSERT INTO addresses VALUES ( '123 First Street', '4GF H1J', 'Our Town', 'Ourcounty', 'US'); SELECT REF(e) FROM addresses e; REF(E) ----------------------------------------------------------------------------------- 00002802097CD1261E51925B60E0340800208254367CD1261E51905B60E034080020825436010101820000 REFTOHEX Syntax Purpose REFTOHEX converts argument expr to a character value containing its hexadecimal equivalent. expr must return a REF. Examples The sample schema oe contains a warehouse_typ. The following example builds on that type to illustrate how to convert the REF value of a column to a character value containing its hexadecimal equivalent: CREATE TABLE warehouse_table OF warehouse_typ (PRIMARY KEY (warehouse_id)); CREATE TABLE location_table (location_number NUMBER, building REF warehouse_typ SCOPE IS warehouse_table); INSERT INTO warehouse_table VALUES (1, 'Downtown', 99); INSERT INTO location_table SELECT 10, REF(w) FROM warehouse_table w; SELECT REFTOHEX(building) FROM location_table; See Also: Oracle Database Concepts for information on REFs REFTOHEX ( expr )
- 298. REGEXP_INSTR 5-136 Oracle Database SQL Reference REFTOHEX(BUILDING) -------------------------------------------------------------------------- 0000220208859B5E9255C31760E034080020825436859B5E9255C21760E034080020825436 REGEXP_INSTR Syntax Purpose REGEXP_INSTR extends the functionality of the INSTR function by letting you search a string for a regular expression pattern. The function evaluates strings using characters as defined by the input character set. It returns an integer indicating the beginning or ending position of the matched substring, depending on the value of the return_option argument. If no match is found, the function returns 0. This function complies with the POSIX regular expression standard and the Unicode Regular Expression Guidelines. For more information, please refer to Appendix C, "Oracle Regular Expression Support". ■ source_char is a character expression that serves as the search value. It is commonly a character column and can be of any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. ■ pattern is the regular expression. It is usually a text literal and can be of any of the datatypes CHAR, VARCHAR2, NCHAR, or NVARCHAR2. It can contain up to 512 bytes. If the datatype of pattern is different from the datatype of source_char, Oracle Database converts pattern to the datatype of source_char. For a listing of the operators you can specify in pattern, please refer to Appendix C, "Oracle Regular Expression Support". ■ position is a positive integer indicating the character of source_char where Oracle should begin the search. The default is 1, meaning that Oracle begins the search at the first character of source_char. ■ occurrence is a positive integer indicating which occurrence of pattern in source_char Oracle should search for. The default is 1, meaning that Oracle searches for the first occurrence of pattern. ■ return_option lets you specify what Oracle should return in relation to the occurrence: – If you specify 0, then Oracle returns the position of the first character of the occurrence. This is the default. – If you specify 1, then Oracle returns the position of the character following the occurrence. ■ match_parameter is a text literal that lets you change the default matching behavior of the function. You can specify one or more of the following values for match_parameter: REGEXP_INSTR ( source_char , pattern , position , occurrence , return_option , match_parameter )
- 299. REGEXP_INSTR Functions 5-137 – 'i' specifies case-insensitive matching. – 'c' specifies case-sensitive matching. – 'n' allows the period (.), which is the match-any-character character, to match the newline character. If you omit this parameter, the period does not match the newline character. – 'm' treats the source string as multiple lines. Oracle interprets ^ and $ as the start and end, respectively, of any line anywhere in the source string, rather than only at the start or end of the entire source string. If you omit this parameter, Oracle treats the source string as a single line. – ’x’ ignores whitespace characters. By default, whitespace characters match themselves. If you specify multiple contradictory values, Oracle uses the last value. For example, if you specify 'ic', then Oracle uses case-sensitive matching. If you specify a character other than those shown above, then Oracle returns an error. If you omit match_parameter, then: – The default case sensitivity is determined by the value of the NLS_SORT parameter. – A period (.) does not match the newline character. – The source string is treated as a single line. Examples The following example examines the string, looking for occurrences of one or more non-blank characters. Oracle begins searching at the first character in the string and returns the starting position (default) of the sixth occurrence of one or more non-blank characters. SELECT REGEXP_INSTR('500 Oracle Parkway, Redwood Shores, CA', '[^ ]+', 1, 6) "REGEXP_INSTR" FROM DUAL; REGEXP_INSTR ------------ 37 The following example examines the string, looking for occurrences of words beginning with s, r, or p, regardless of case, followed by any six alphabetic characters. Oracle begins searching at the third character in the string and returns the position in the string of the character following the second occurrence of a seven-letter word beginning with s, r, or p, regardless of case. SELECT REGEXP_INSTR('500 Oracle Parkway, Redwood Shores, CA', '[s|r|p][[:alpha:]]{6}', 3, 2, 1, 'i') "REGEXP_INSTR" FROM DUAL; REGEXP_INSTR See Also: ■ INSTR on page 5-79 and REGEXP_SUBSTR on page 5-140 ■ REGEXP_REPLACE on page 5-138 and REGEXP_LIKE Condition on page 7-17
- 300. REGEXP_REPLACE 5-138 Oracle Database SQL Reference ------------ 28 REGEXP_REPLACE Syntax Purpose REGEXP_REPLACE extends the functionality of the REPLACE function by letting you search a string for a regular expression pattern. By default, the function returns source_char with every occurrence of the regular expression pattern replaced with replace_string. The string returned is in the same character set as source_char. The function returns VARCHAR2 if the first argument is not a LOB and returns CLOB if the first argument is a LOB. This function complies with the POSIX regular expression standard and the Unicode Regular Expression Guidelines. For more information, please refer to Appendix C, "Oracle Regular Expression Support". ■ source_char is a character expression that serves as the search value. It is commonly a character column and can be of any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB or NCLOB. ■ pattern is the regular expression. It is usually a text literal and can be of any of the datatypes CHAR, VARCHAR2, NCHAR, or NVARCHAR2. It can contain up to 512 bytes. If the datatype of pattern is different from the datatype of source_char, Oracle Database converts pattern to the datatype of source_char. For a listing of the operators you can specify in pattern, please refer to Appendix C, "Oracle Regular Expression Support". ■ replace_string can be of any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. If replace_string is a CLOB or NCLOB, then Oracle truncates replace_string to 32K. The replace_string can contain up to 500 backreferences to subexpressions in the form n, where n is a number from 1 to 9. If n is the backslash character in replace_string, then you must precede it with the escape character (). For more information on backreference expressions, please refer to the notes to "Oracle Regular Expression Support", Table C–1 on page C-1. ■ position is a positive integer indicating the character of source_char where Oracle should begin the search. The default is 1, meaning that Oracle begins the search at the first character of source_char. ■ occurrence is a nonnegative integer indicating the occurrence of the replace operation: – If you specify 0, then Oracle replaces all occurrences of the match. – If you specify a positive integer n, then Oracle replaces the nth occurrence. REGEXP_REPLACE ( source_char , pattern , replace_string , position , occurrence , match_parameter )
- 301. REGEXP_REPLACE Functions 5-139 ■ match_parameter is a text literal that lets you change the default matching behavior of the function. This argument affects only the matching process and has no effect on replace_string. You can specify one or more of the following values for match_parameter: – 'i' specifies case-insensitive matching. – 'c' specifies case-sensitive matching. – 'n' allows the period (.), which is the match-any-character character, to match the newline character. If you omit this parameter, the period does not match the newline character. – 'm' treats the source string as multiple lines. Oracle interprets ^ and $ as the start and end, respectively, of any line anywhere in the source string, rather than only at the start or end of the entire source string. If you omit this parameter, Oracle treats the source string as a single line. – ’x’ ignores whitespace characters. By default, whitespace characters match themselves. If you specify multiple contradictory values, Oracle uses the last value. For example, if you specify 'ic', then Oracle uses case-sensitive matching. If you specify a character other than those shown above, then Oracle returns an error. If you omit match_parameter, then: – The default case sensitivity is determined by the value of the NLS_SORT parameter. – A period (.) does not match the newline character. – The source string is treated as a single line. Examples The following example examines phone_number, looking for the pattern xxx.xxx.xxxx. Oracle reformats this pattern with (xxx) xxx-xxxx. SELECT REGEXP_REPLACE(phone_number, '([[:digit:]]{3}).([[:digit:]]{3}).([[:digit:]]{4})', '(1) 2-3') "REGEXP_REPLACE" FROM employees; REGEXP_REPLACE -------------------------------------------------------------------------------- (515) 123-4567 (515) 123-4568 (515) 123-4569 (590) 423-4567 . . . The following example examines country_name. Oracle puts a space after each non-null character in the string. SELECT See Also: ■ REPLACE on page 5-148 ■ REGEXP_INSTR on page 5-136, REGEXP_SUBSTR on page 5-140, and REGEXP_LIKE Condition on page 7-17
- 302. REGEXP_SUBSTR 5-140 Oracle Database SQL Reference REGEXP_REPLACE(country_name, '(.)', '1 ') "REGEXP_REPLACE" FROM countries; REGEXP_REPLACE -------------------------------------------------------------------------------- A r g e n t i n a A u s t r a l i a B e l g i u m B r a z i l C a n a d a . . . The following example examines the string, looking for two or more spaces. Oracle replaces each occurrence of two or more spaces with a single space. SELECT REGEXP_REPLACE('500 Oracle Parkway, Redwood Shores, CA', '( ){2,}', ' ') "REGEXP_REPLACE" FROM DUAL; REGEXP_REPLACE -------------------------------------- 500 Oracle Parkway, Redwood Shores, CA REGEXP_SUBSTR Syntax Purpose REGEXP_SUBSTR extends the functionality of the SUBSTR function by letting you search a string for a regular expression pattern. It is also similar to REGEXP_INSTR, but instead of returning the position of the substring, it returns the substring itself. This function is useful if you need the contents of a match string but not its position in the source string. The function returns the string as VARCHAR2 or CLOB data in the same character set as source_char. This function complies with the POSIX regular expression standard and the Unicode Regular Expression Guidelines. For more information, please refer to Appendix C, "Oracle Regular Expression Support". ■ source_char is a character expression that serves as the search value. It is commonly a character column and can be of any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. ■ pattern is the regular expression. It is usually a text literal and can be of any of the datatypes CHAR, VARCHAR2, NCHAR, or NVARCHAR2. It can contain up to 512 bytes. If the datatype of pattern is different from the datatype of source_char, Oracle Database converts pattern to the datatype of source_char. For a listing REGEXP_SUBSTR ( source_char , pattern , position , occurrence , match_parameter )
- 303. REGEXP_SUBSTR Functions 5-141 of the operators you can specify in pattern, please refer to Appendix C, "Oracle Regular Expression Support". ■ position is a positive integer indicating the character of source_char where Oracle should begin the search. The default is 1, meaning that Oracle begins the search at the first character of source_char. ■ occurrence is a positive integer indicating which occurrence of pattern in source_char Oracle should search for. The default is 1, meaning that Oracle searches for the first occurrence of pattern. ■ match_parameter is a text literal that lets you change the default matching behavior of the function. You can specify one or more of the following values for match_parameter: – 'i' specifies case-insensitive matching. – 'c' specifies case-sensitive matching. – 'n' allows the period (.), which is the match-any-character character, to match the newline character. If you omit this parameter, the period does not match the newline character. – 'm' treats the source string as multiple lines. Oracle interprets ^ and $ as the start and end, respectively, of any line anywhere in the source string, rather than only at the start or end of the entire source string. If you omit this parameter, Oracle treats the source string as a single line. – ’x’ ignores whitespace characters. By default, whitespace characters match themselves. If you specify multiple contradictory values, Oracle uses the last value. For example, if you specify 'ic', then Oracle uses case-sensitive matching. If you specify a character other than those shown above, then Oracle returns an error. If you omit match_parameter, then: – The default case sensitivity is determined by the value of the NLS_SORT parameter. – A period (.) does not match the newline character. – The source string is treated as a single line. Examples The following example examines the string, looking for the first substring bounded by commas. Oracle Database searches for a comma followed by one or more occurrences of non-comma characters followed by a comma. Oracle returns the substring, including the leading and trailing commas. SELECT REGEXP_SUBSTR('500 Oracle Parkway, Redwood Shores, CA', ',[^,]+,') "REGEXPR_SUBSTR" FROM DUAL; REGEXPR_SUBSTR ----------------- See Also: ■ SUBSTR on page 5-173 and REGEXP_INSTR on page 5-136 ■ REGEXP_REPLACE on page 5-138, and REGEXP_LIKE Condition on page 7-17
- 304. REGR_ (Linear Regression) Functions 5-142 Oracle Database SQL Reference , Redwood Shores, The following example examines the string, looking for http:// followed by a substring of one or more alphanumeric characters and optionally, a period (.). Oracle searches for a minimum of three and a maximum of four occurrences of this substring between http:// and either a slash (/) or the end of the string. SELECT REGEXP_SUBSTR('http://www.oracle.com/products', 'http://([[:alnum:]]+.?){3,4}/?') "REGEXP_SUBSTR" FROM DUAL; REGEXP_SUBSTR ---------------------- http://www.oracle.com/ REGR_ (Linear Regression) Functions The linear regression functions are: ■ REGR_SLOPE ■ REGR_INTERCEPT ■ REGR_COUNT ■ REGR_R2 ■ REGR_AVGX ■ REGR_AVGY ■ REGR_SXX ■ REGR_SYY ■ REGR_SXY Syntax linear_regr::= REGR_SLOPE REGR_INTERCEPT REGR_COUNT REGR_R2 REGR_AVGX REGR_AVGY REGR_SXX REGR_SYY REGR_SXY ( expr1 , expr2 ) OVER ( analytic_clause )
- 305. REGR_ (Linear Regression) Functions Functions 5-143 Purpose The linear regression functions fit an ordinary-least-squares regression line to a set of number pairs. You can use them as both aggregate and analytic functions. These functions take as arguments any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. Oracle determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype, and returns that datatype. Oracle applies the function to the set of (expr1, expr2) pairs after eliminating all pairs for which either expr1 or expr2 is null. Oracle computes all the regression functions simultaneously during a single pass through the data. expr1 is interpreted as a value of the dependent variable (a y value), and expr2 is interpreted as a value of the independent variable (an x value). ■ REGR_SLOPE returns the slope of the line. The return value is a numeric datatype and can be null. After the elimination of null (expr1, expr2) pairs, it makes the following computation: COVAR_POP(expr1, expr2) / VAR_POP(expr2) ■ REGR_INTERCEPT returns the y-intercept of the regression line. The return value is a numeric datatype and can be null. After the elimination of null (expr1, expr2) pairs, it makes the following computation: AVG(expr1) - REGR_SLOPE(expr1, expr2) * AVG(expr2) ■ REGR_COUNT returns an integer that is the number of non-null number pairs used to fit the regression line. ■ REGR_R2 returns the coefficient of determination (also called R-squared or goodness of fit) for the regression. The return value is a numeric datatype and can be null. VAR_POP(expr1) and VAR_POP(expr2) are evaluated after the elimination of null pairs. The return values are: NULL if VAR_POP(expr2) = 0 1 if VAR_POP(expr1) = 0 and VAR_POP(expr2) != 0 POWER(CORR(expr1,expr),2) if VAR_POP(expr1) > 0 and VAR_POP(expr2 != 0 All of the remaining regression functions return a numeric datatype and can be null: ■ REGR_AVGX evaluates the average of the independent variable (expr2) of the regression line. It makes the following computation after the elimination of null (expr1, expr2) pairs: See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: "Aggregate Functions" on page 5-8 and "About SQL Expressions" on page 6-1 for information on valid forms of expr See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion and "Numeric Precedence" on page 2-13 for information on numeric precedence
- 306. REGR_ (Linear Regression) Functions 5-144 Oracle Database SQL Reference AVG(expr2) ■ REGR_AVGY evaluates the average of the dependent variable (expr1) of the regression line. It makes the following computation after the elimination of null (expr1, expr2) pairs: AVG(expr1) REGR_SXY, REGR_SXX, REGR_SYY are auxiliary functions that are used to compute various diagnostic statistics. ■ REGR_SXX makes the following computation after the elimination of null (expr1, expr2) pairs: REGR_COUNT(expr1, expr2) * VAR_POP(expr2) ■ REGR_SYY makes the following computation after the elimination of null (expr1, expr2) pairs: REGR_COUNT(expr1, expr2) * VAR_POP(expr1) ■ REGR_SXY makes the following computation after the elimination of null (expr1, expr2) pairs: REGR_COUNT(expr1, expr2) * COVAR_POP(expr1, expr2) The following examples are based on the sample tables sh.sales and sh.products. General Linear Regression Example The following example provides a comparison of the various linear regression functions used in their analytic form. The analytic form of these functions can be useful when you want to use regression statistics for calculations such as finding the salary predicted for each employee by the model. The sections that follow on the individual linear regression functions contain examples of the aggregate form of these functions. SELECT job_id, employee_id ID, salary, REGR_SLOPE(SYSDATE-hire_date, salary) OVER (PARTITION BY job_id) slope, REGR_INTERCEPT(SYSDATE-hire_date, salary) OVER (PARTITION BY job_id) intcpt, REGR_R2(SYSDATE-hire_date, salary) OVER (PARTITION BY job_id) rsqr, REGR_COUNT(SYSDATE-hire_date, salary) OVER (PARTITION BY job_id) count, REGR_AVGX(SYSDATE-hire_date, salary) OVER (PARTITION BY job_id) avgx, REGR_AVGY(SYSDATE-hire_date, salary) OVER (PARTITION BY job_id) avgy FROM employees WHERE department_id in (50, 80) ORDER BY job_id, employee_id; JOB_ID ID SALARY SLOPE INTCPT RSQR COUNT AVGX AVGY ---------- ----- ---------- ----- --------- ----- ------ ---------- --------- SA_MAN 145 14000 .355 -1707.035 .832 5 12200.000 2626.589 SA_MAN 146 13500 .355 -1707.035 .832 5 12200.000 2626.589 SA_MAN 147 12000 .355 -1707.035 .832 5 12200.000 2626.589 SA_MAN 148 11000 .355 -1707.035 .832 5 12200.000 2626.589 SA_MAN 149 10500 .355 -1707.035 .832 5 12200.000 2626.589 SA_REP 150 10000 .257 404.763 .647 29 8396.552 2561.244
- 307. REGR_ (Linear Regression) Functions Functions 5-145 SA_REP 151 9500 .257 404.763 .647 29 8396.552 2561.244 SA_REP 152 9000 .257 404.763 .647 29 8396.552 2561.244 SA_REP 153 8000 .257 404.763 .647 29 8396.552 2561.244 SA_REP 154 7500 .257 404.763 .647 29 8396.552 2561.244 SA_REP 155 7000 .257 404.763 .647 29 8396.552 2561.244 SA_REP 156 10000 .257 404.763 .647 29 8396.552 2561.244 ... REGR_SLOPE and REGR_INTERCEPT Examples The following example calculates the slope and regression of the linear regression model for time employed (SYSDATE - hire_date) and salary using the sample table hr.employees. Results are grouped by job_id. SELECT job_id, REGR_SLOPE(SYSDATE-hire_date, salary) slope, REGR_INTERCEPT(SYSDATE-hire_date, salary) intercept FROM employees WHERE department_id in (50,80) GROUP BY job_id ORDER BY job_id; JOB_ID SLOPE INTERCEPT ---------- ---------- ---------- JOB_ID SLOPE INTERCEPT ---------- ----- ------------ SA_MAN .355 -1707.030762 SA_REP .257 404.767151 SH_CLERK .745 159.015293 ST_CLERK .904 134.409050 ST_MAN .479 -570.077291 REGR_COUNT Examples The following example calculates the count of by job_id for time employed (SYSDATE - hire_date) and salary using the sample table hr.employees. Results are grouped by job_id. SELECT job_id, REGR_COUNT(SYSDATE-hire_date, salary) count FROM employees WHERE department_id in (30, 50) GROUP BY job_id; JOB_ID COUNT ---------- ------ ST_MAN 5 PU_MAN 1 SH_CLERK 20 PU_CLERK 5 ST_CLERK 20 REGR_R2 Examples The following example calculates the coefficient of determination the linear regression of time employed (SYSDATE - hire_date) and salary using the sample table hr.employees: SELECT job_id, REGR_R2(SYSDATE-hire_date, salary) Regr_R2 FROM employees WHERE department_id in (80, 50) GROUP by job_id;
- 308. REMAINDER 5-146 Oracle Database SQL Reference JOB_ID REGR_R2 ---------- ----------- ST_MAN .694185080 SH_CLERK .879799698 SA_MAN .832447480 SA_REP .647007156 ST_CLERK .742808493 REGR_AVGY and REGR_AVGX Examples The following example calculates the average values for time employed (SYSDATE - hire_date) and salary using the sample table hr.employees. Results are grouped by job_id: SELECT job_id, REGR_AVGY(SYSDATE-hire_date, salary) avgy, REGR_AVGX(SYSDATE-hire_date, salary) avgx FROM employees WHERE department_id in (30,50) GROUP BY job_id; JOB_ID AVGY AVGX ---------- --------------- ------ ST_MAN 2899.055555556 7280 PU_MAN 3785.455555556 11000 SH_CLERK 2531.955555556 4925 PU_CLERK 2709.255555556 2780 ST_CLERK 2631.605555556 2785 REGR_SXY, REGR_SXX, and REGR_SYY Examples The following example calculates three types of diagnostic statistics for the linear regression of time employed (SYSDATE - hire_date) and salary using the sample table hr.employees: SELECT job_id, REGR_SXY(SYSDATE-hire_date, salary) regr_sxy, REGR_SXX(SYSDATE-hire_date, salary) regr_sxx, REGR_SYY(SYSDATE-hire_date, salary) regr_syy FROM employees WHERE department_id in (80, 50) GROUP BY job_id ORDER BY job_id; JOB_ID REGR_SXY REGR_SXX REGR_SYY ---------- ---------- ----------- ---------- SA_MAN 3303500 9300000.0 1409642 SA_REP 16819665.5 65489655.2 6676562.55 SH_CLERK 4248650 5705500.0 3596039 ST_CLERK 3531545 3905500.0 4299084.55 ST_MAN 2180460 4548000.0 1505915.2 REMAINDER Syntax REMAINDER ( n2 , n1 )
- 309. REPLACE Functions 5-147 Purpose REMAINDER returns the remainder of n2 divided by n1. This function takes as arguments any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. Oracle determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype, and returns that datatype. The MOD function is similar to REMAINDER except that it uses FLOOR in its formula, whereas REMAINDER uses ROUND. Please refer to MOD on page 5-97. ■ If n1 = 0 or m2 = infinity, then Oracle returns – An error if the arguments are of type NUMBER – NaN if the arguments are BINARY_FLOAT or BINARY_DOUBLE. ■ If n1 != 0, then the remainder is n2 - (n1*N) where N is the integer nearest n2/n1. ■ If n2 is a floating-point number, and if the remainder is 0, then the sign of the remainder is the sign of n2. Remainders of 0 are unsigned for NUMBER values. Examples Using table float_point_demo, created for the TO_BINARY_DOUBLE "Examples" on page 5-189, the following example divides two floating-point numbers and returns the remainder of that operation: SELECT bin_float, bin_double, REMAINDER(bin_float, bin_double) FROM float_point_demo; BIN_FLOAT BIN_DOUBLE REMAINDER(BIN_FLOAT,BIN_DOUBLE) ---------- ---------- ------------------------------- 1.235E+003 1.235E+003 5.859E-005 REPLACE Syntax Purpose REPLACE returns char with every occurrence of search_string replaced with replacement_string. If replacement_string is omitted or null, then all occurrences of search_string are removed. If search_string is null, then char is returned. Both search_string and replacement_string, as well as char, can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The string returned is in the same character set as char. The function returns VARCHAR2 if the first argument is not a LOB and returns CLOB if the first argument is a LOB. See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion and "Numeric Precedence" on page 2-13 for information on numeric precedence REPLACE ( char , search_string , replacement_string )
- 310. ROUND (number) 5-148 Oracle Database SQL Reference REPLACE provides functionality related to that provided by the TRANSLATE function. TRANSLATE provides single-character, one-to-one substitution. REPLACE lets you substitute one string for another as well as to remove character strings. Examples The following example replaces occurrences of J with BL: SELECT REPLACE('JACK and JUE','J','BL') "Changes" FROM DUAL; Changes -------------- BLACK and BLUE ROUND (number) Syntax round_number::= Purpose ROUND returns n rounded to integer places to the right of the decimal point. If you omit integer, then n is rounded to 0 places. The argument integer can be negative to round off digits left of the decimal point. n can be any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The argument integer must be an integer. If you omit integer, then the function returns the same datatype as the numeric datatype of the argument. If you include integer, then the function returns NUMBER. For NUMBER values, the value n is rounded away from 0 (for example, to x+1 when x.5 is positive and to x-1 when x.5 is negative). For BINARY_FLOAT and BINARY_DOUBLE values, the function rounds to the nearest even value. Please refer to the examples that follow. Examples The following example rounds a number to one decimal point: SELECT ROUND(15.193,1) "Round" FROM DUAL; Round ---------- 15.2 The following example rounds a number one digit to the left of the decimal point: SELECT ROUND(15.193,-1) "Round" FROM DUAL; Round See Also: TRANSLATE on page 5-203 See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion ROUND ( n , integer )
- 311. ROW_NUMBER Functions 5-149 ---------- 20 The following examples illustrate the difference between rounding NUMBER and floating-point number values. NUMBER values are rounded up (for positive values), whereas floating-point numbers are rounded toward the nearest even value: SELECT ROUND(1.5), ROUND(2.5) FROM DUAL; ROUND(1.5) ROUND(2.5) ---------- ---------- 2 3 SELECT ROUND(1.5f), ROUND(2.5f) FROM DUAL; ROUND(1.5F) ROUND(2.5F) ----------- ----------- 2.0E+000 2.0E+000 ROUND (date) Syntax round_date::= Purpose ROUND returns date rounded to the unit specified by the format model fmt. The value returned is always of datatype DATE, even if you specify a different datetime datatype for date. If you omit fmt, then date is rounded to the nearest day. The date expression must resolve to a DATE value. Examples The following example rounds a date to the first day of the following year: SELECT ROUND (TO_DATE ('27-OCT-00'),'YEAR') "New Year" FROM DUAL; New Year --------- 01-JAN-01 ROW_NUMBER Syntax See Also: "ROUND and TRUNC Date Functions" on page 5-235 for the permitted format models to use in fmt ROUND ( date , fmt ) ROW_NUMBER ( ) OVER ( query_partition_clause order_by_clause )
- 312. ROW_NUMBER 5-150 Oracle Database SQL Reference Purpose ROW_NUMBER is an analytic function. It assigns a unique number to each row to which it is applied (either each row in the partition or each row returned by the query), in the ordered sequence of rows specified in the order_by_clause, beginning with 1. By nesting a subquery using ROW_NUMBER inside a query that retrieves the ROW_ NUMBER values for a specified range, you can find a precise subset of rows from the results of the inner query. This use of the function lets you implement top-N, bottom-N, and inner-N reporting. For consistent results, the query must ensure a deterministic sort order. You cannot use ROW_NUMBER or any other analytic function for expr. That is, you cannot nest analytic functions, but you can use other built-in function expressions for expr. Please refer to "About SQL Expressions" on page 6-1 for information on valid forms of expr. Examples For each department in the sample table oe.employees, the following example assigns numbers to each row in order of employee's hire date: SELECT department_id, last_name, employee_id, ROW_NUMBER() OVER (PARTITION BY department_id ORDER BY employee_id) AS emp_id FROM employees; DEPARTMENT_ID LAST_NAME EMPLOYEE_ID EMP_ID ------------- ------------------------- ----------- ---------- 10 Whalen 200 1 20 Hartstein 201 1 20 Fay 202 2 30 Raphaely 114 1 30 Khoo 115 2 30 Baida 116 3 30 Tobias 117 4 30 Himuro 118 5 30 Colmenares 119 6 40 Mavris 203 1 . . . 100 Popp 113 6 110 Higgins 205 1 110 Gietz 206 2 ROW_NUMBER is a nondeterministic function. However, employee_id is a unique key, so the results of this application of the function are deterministic. The following inner-N query selects all rows from the employees table but returns only the fifty-first through one-hundredth row: SELECT last_name FROM (SELECT last_name, ROW_NUMBER() OVER (ORDER BY last_name) R FROM employees) WHERE R BETWEEN 51 and 100; See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: FIRST_VALUE on page 5-70 and LAST_VALUE on page 5-83 for examples of nondeterministic behavior
- 313. RPAD Functions 5-151 ROWIDTOCHAR Syntax Purpose ROWIDTOCHAR converts a rowid value to VARCHAR2 datatype. The result of this conversion is always 18 characters long. Examples The following example converts a rowid value in the employees table to a character value. (Results vary for each build of the sample database.) SELECT ROWID FROM employees WHERE ROWIDTOCHAR(ROWID) LIKE '%JAAB%'; ROWID ------------------ AAAFfIAAFAAAABSAAb ROWIDTONCHAR Syntax Purpose ROWIDTONCHAR converts a rowid value to NVARCHAR2 datatype. The result of this conversion is always in the national character set and is 18 characters long. Examples The following example converts a rowid value to an NVARCHAR2 string: SELECT LENGTHB( ROWIDTONCHAR(ROWID) ), ROWIDTONCHAR(ROWID) FROM employees; LENGTHB(ROWIDTONCHAR(ROWID)) ROWIDTONCHAR(ROWID ---------------------------- ------------------ 36 AAAFfIAAFAAAABSAAA . . . RPAD Syntax Purpose RPAD returns expr1, right-padded to length n characters with expr2, replicated as many times as necessary. This function is useful for formatting the output of a query. ROWIDTOCHAR ( rowid ) ROWIDTONCHAR ( rowid ) RPAD ( expr1 , n , expr2 )
- 314. RTRIM 5-152 Oracle Database SQL Reference Both expr1 and expr2 can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The string returned is of VARCHAR2 datatype if expr1 is a character datatype and a LOB if expr1 is a LOB datatype. The string returned is in the same character set as expr1. The argument n must be a NUMBER integer or a value that can be implicitly converted to a NUMBER integer. expr1 cannot be null. If you do not specify expr2, then it defaults to a single blank. If expr1 is longer than n, then this function returns the portion of expr1 that fits in n. The argument n is the total length of the return value as it is displayed on your terminal screen. In most character sets, this is also the number of characters in the return value. However, in some multibyte character sets, the display length of a character string can differ from the number of characters in the string. Examples The following example creates a simple chart of salary amounts by padding a single space with asterisks: SELECT last_name, RPAD(' ', salary/1000/1, '*') "Salary" FROM employees WHERE department_id = 80 ORDER BY last_name; LAST_NAME Salary ------------------------- --------------- Abel ********** Ande ***** Banda ***** Bates ****** Bernstein ******** Bloom ********* Cambrault ********** Cambrault ****** Doran ****** Errazuriz *********** Fox ******** Greene ******** Hall ******** Hutton ******* Johnson ***** King ********* . . . RTRIM Syntax Purpose RTRIM removes from the right end of char all of the characters that appear in set. This function is useful for formatting the output of a query. If you do not specify set, then it defaults to a single blank. If char is a character literal, then you must enclose it in single quotes. RTRIM works similarly to LTRIM. RTRIM ( char , set )
- 315. SCN_TO_TIMESTAMP Functions 5-153 Both char and set can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The string returned is of VARCHAR2 datatype if char is a character datatype and a LOB if char is a LOB datatype. Examples The following example trims all the right-most occurrences of period, slash, and equal sign from a string: SELECT RTRIM('BROWNING: ./=./=./=./=./=.=','/=.') "RTRIM example" FROM DUAL; RTRIM exam ---------- BROWNING: SCN_TO_TIMESTAMP Syntax Purpose SCN_TO_TIMESTAMP takes as an argument a number that evaluates to a system change number (SCN), and returns the approximate timestamp associated with that SCN. The returned value is of TIMESTAMP datatype. This function is useful any time you want to know the timestamp associated with an SCN. For example, it can be used in conjunction with the ORA_ROWSCN pseudocolumn to associate a timestamp with the most recent change to a row. Examples The following example uses the ORA_ROWSCN pseudocolumn to determine the system change number of the last update to a row and uses SCN_TO_TIMESTAMP to convert that SCN to a timestamp: SELECT SCN_TO_TIMESTAMP(ORA_ROWSCN) FROM employees WHERE employee_id = 188; You could use such a query to convert a system change number to a timestamp for use in an Oracle Flashback Query: SELECT salary FROM employees WHERE employee_id = 188; SALARY ---------- 3800 UPDATE employees SET salary = salary*10 WHERE employee_id = 188; COMMIT; SELECT salary FROM employees WHERE employee_id = 188; SALARY ---------- 38000 See Also: LTRIM on page 5-91 See Also: ORA_ROWSCN Pseudocolumn on page 3-8 and TIMESTAMP_TO_SCN on page 5-187 SCN_TO_TIMESTAMP ( number )
- 316. SESSIONTIMEZONE 5-154 Oracle Database SQL Reference SELECT SCN_TO_TIMESTAMP(ORA_ROWSCN) FROM employees WHERE employee_id = 188; SCN_TO_TIMESTAMP(ORA_ROWSCN) --------------------------------------------------------------------------- 28-AUG-03 01.58.01.000000000 PM FLASHBACK TABLE employees TO TIMESTAMP TO_TIMESTAMP('28-AUG-03 01.00.00.000000000 PM'); SELECT salary FROM employees WHERE employee_id = 188; SALARY ---------- 3800 SESSIONTIMEZONE Syntax Purpose SESSIONTIMEZONE returns the time zone of the current session. The return type is a time zone offset (a character type in the format '[+|]TZH:TZM') or a time zone region name, depending on how the user specified the session time zone value in the most recent ALTER SESSION statement. Examples The following example returns the time zone of the current session: SELECT SESSIONTIMEZONE FROM DUAL; SESSION ------- -08:00 SET Syntax Purpose SET converts a nested table into a set by eliminating duplicates. The function returns a nested table whose elements are distinct from one another. The returned nested table is of the same type as the input nested table. The element types of the nested table must be comparable. Please refer to "Comparison Conditions" on page 7-4 for information on the comparability of nonscalar types. Note: You can set the default client session time zone using the ORA_ SDTZ environment variable. Please refer to Oracle Database Globalization Support Guide for more information on this variable. SESSIONTIMEZONE SET ( nested_table )
- 317. SIGN Functions 5-155 Example The following example selects from the customers_demo table the unique elements of the cust_address_ntab nested table column: SELECT customer_id, SET(cust_address_ntab) address FROM customers_demo; CUSTOMER_ID ADDRESS(STREET_ADDRESS, POSTAL_CODE, CITY, STATE_PROVINCE, COUNTRY_ID) ----------- ------------------------------------------------------------------------ 101 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('514 W Superior St', '46901', 'Kokomo', 'IN', 'US')) 102 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('2515 Bloyd Ave', '46218', 'Indianapolis', 'IN', 'US')) 103 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('8768 N State Rd 37', '47404', 'Bloomington', 'IN', 'US')) 104 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('6445 Bay Harbor Ln', '46254', 'Indianapolis', 'IN', 'US')) 105 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('4019 W 3Rd St', '47404', 'Bloomington', 'IN', 'US')) . . . The preceding example requires the table customers_demo and a nested table column containing data. Please refer to "Multiset Operators" on page 4-1 to create this table and nested table column. SIGN Syntax Purpose SIGN returns the sign of n. This function takes as an argument any numeric datatype, or any nonnumeric datatype that can be implicitly converted to NUMBER, and returns NUMBER. For value of NUMBER type, the sign is: ■ -1 if n<0 ■ 0 if n=0 ■ 1 if n>0 For binary floating-point numbers (BINARY_FLOAT and BINARY_DOUBLE), this function returns the sign bit of the number. The sign bit is: ■ -1 if n<0 ■ +1 if n>=0 or n=NaN Examples The following example indicates that the argument of the function (-15) is <0: SELECT SIGN(-15) "Sign" FROM DUAL; Sign ---------- -1 SIGN ( n )
- 318. SIN 5-156 Oracle Database SQL Reference SIN Syntax Purpose SIN returns the sine of n (an angle expressed in radians). This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. If the argument is BINARY_ FLOAT, then the function returns BINARY_DOUBLE. Otherwise the function returns the same numeric datatype as the argument. Examples The following example returns the sine of 30 degrees: SELECT SIN(30 * 3.14159265359/180) "Sine of 30 degrees" FROM DUAL; Sine of 30 degrees ------------------ .5 SINH Syntax Purpose SINH returns the hyperbolic sine of n. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. If the argument is BINARY_ FLOAT, then the function returns BINARY_DOUBLE. Otherwise the function returns the same numeric datatype as the argument. Examples The following example returns the hyperbolic sine of 1: SELECT SINH(1) "Hyperbolic sine of 1" FROM DUAL; Hyperbolic sine of 1 -------------------- 1.17520119 See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion SIN ( n ) SINH ( n )
- 319. SOUNDEX Functions 5-157 SOUNDEX Syntax Purpose SOUNDEX returns a character string containing the phonetic representation of char. This function lets you compare words that are spelled differently, but sound alike in English. The phonetic representation is defined in The Art of Computer Programming, Volume 3: Sorting and Searching, by Donald E. Knuth, as follows: 1. Retain the first letter of the string and remove all other occurrences of the following letters: a, e, h, i, o, u, w, y. 2. Assign numbers to the remaining letters (after the first) as follows: b, f, p, v = 1 c, g, j, k, q, s, x, z = 2 d, t = 3 l = 4 m, n = 5 r = 6 3. If two or more letters with the same number were adjacent in the original name (before step 1), or adjacent except for any intervening h and w, then omit all but the first. 4. Return the first four bytes padded with 0. char can be of any of the datatypes CHAR, VARCHAR2, NCHAR, or NVARCHAR2. The return value is the same datatype as char. This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion. Examples The following example returns the employees whose last names are a phonetic representation of "Smyth": SELECT last_name, first_name FROM hr.employees WHERE SOUNDEX(last_name) = SOUNDEX('SMYTHE'); LAST_NAME FIRST_NAME ---------- ---------- Smith Lindsey Smith William See Also: "Datatype Comparison Rules" on page 2-37 for more information. SOUNDEX ( char )
- 320. SQRT 5-158 Oracle Database SQL Reference SQRT Syntax Purpose SQRT returns the square root of n. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument. ■ If n resolves to a NUMBER, then the value n cannot be negative. SQRT returns a real number. ■ If n resolves to a binary floating-point number (BINARY_FLOAT or BINARY_ DOUBLE): – If n >= 0, the result is positive. – If n = -0, the result is -0. – If n < 0, the result is NaN. Examples The following example returns the square root of 26: SELECT SQRT(26) "Square root" FROM DUAL; Square root ----------- 5.09901951 STATS_BINOMIAL_TEST Syntax Purpose STATS_BINOMIAL_TEST is an exact probability test used for dichotomous variables, where only two possible values exist. It tests the difference between a sample proportion and a given proportion. The sample size in such tests is usually small. This function takes four arguments: expr1 is the sample being examined. expr2 contains the values for which the proportion is expected to be, and p is a proportion to See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion SQRT ( n ) STATS_BINOMIAL_TEST ( expr1 , expr2 , p , TWO_SIDED_PROB EXACT_PROB ONE_SIDED_PROB_OR_MORE ONE_SIDED_PROB_OR_LESS )
- 321. STATS_CROSSTAB Functions 5-159 test against. The fourth argument is a return value of type VARCHAR2. If you omit the fourth argument, the default is TWO_SIDED_PROB. The meaning of the return values is shown in Table 5–3. EXACT_PROB gives the probability of getting exactly proportion p. In cases where you want to test whether the proportion found in the sample is significantly different from a 50-50 split, p would normally be 0.50. If you want to test only whether the proportion is different, then use the return value TWO_SIDED_PROB. If your test is whether the proportion is more than the value of expr2, then use the return value ONE_SIDED_PROB_OR_MORE. If the test is to determine whether the proportion of expr2 is less, then use the return value ONE_SIDED_PROB_OR_LESS. STATS_BINOMIAL_TEST Example The following example determines the probability that reality exactly matches the number of men observed under the assumption that 69% of the population is composed of men: SELECT AVG(DECODE(cust_gender, 'M', 1, 0)) real_proportion, STATS_BINOMIAL_TEST (cust_gender, 'M', 0.68, 'EXACT_PROB') exact, STATS_BINOMIAL_TEST (cust_gender, 'M', 0.68, 'ONE_SIDED_PROB_OR_LESS') prob_or_less FROM sh.customers; STATS_CROSSTAB Syntax Table 5–3 STATS_BINOMIAL Return Values Return Value Meaning TWO_SIDED_PROB The probability that the given population proportion, p, could result in the observed proportion or a more extreme one. EXACT_PROB The probability that the given population proportion, p, could result in exactly the observed proportion. ONE_SIDED_PROB_OR_MORE The probability that the given population proportion, p, could result in the observed proportion or a larger one. ONE_SIDED_PROB_OR_LESS The probability that the given population proportion, p, could result in the observed proportion or a smaller one. STATS_CROSSTAB ( expr1 , expr2 , CHISQ_OBS CHISQ_SIG CHISQ_DF PHI_COEFFICIENT CRAMERS_V CONT_COEFFICIENT COHENS_K )
- 322. STATS_F_TEST 5-160 Oracle Database SQL Reference Purpose Crosstabulation (commonly called crosstab) is a method used to analyze two nominal variables. The STATS_CROSSTAB function takes three arguments: two expressions and a return value of type VARCHAR2. expr1 and expr2 are the two variables being analyzed. The function returns one number, determined by the value of the third argument. If you omit the third argument, the default is CHISQ_SIG. The meaning of the return values is shown in Table 5–4. STATS_CROSSTAB Example The following example determines the strength of the association between gender and income level: SELECT STATS_CROSSTAB (cust_gender, cust_income_level, 'CHISQ_OBS') chi_squared, STATS_CROSSTAB (cust_gender, cust_income_level, 'CHISQ_SIG') p_value, STATS_CROSSTAB (cust_gender, cust_income_level, 'PHI_COEFFICIENT') phi_coefficient FROM sh.customers; CHI_SQUARED P_VALUE PHI_COEFFICIENT ----------- ---------- --------------- 251.690705 1.2364E-47 .067367056 STATS_F_TEST Syntax Purpose STATS_F_TEST tests whether two variances are significantly different. The observed value of f is the ratio of one variance to the other, so values very different from 1 usually indicate significant differences. Table 5–4 STATS_CROSSTAB Return Values Return Value Meaning CHISQ_OBS Observed value of chi-squared CHISQ_SIG Significance of observed chi-squared CHISQ_DF Degree of freedom for chi-squared PHI_COEFFICIENT Phi coefficient CRAMERS_V Cramer's V statistic CONT_COEFFICIENT Contingency coefficient COHENS_K Cohen's kappa STATS_F_TEST ( expr1 , expr2 , STATISTIC DF_NUM DF_DEN ONE_SIDED_SIG expr3 TWO_SIDED_SIG )
- 323. STATS_KS_TEST Functions 5-161 This function takes three arguments: expr1 is the grouping or independent variable and expr2 is the sample of values. The function returns one number, determined by the value of the third argument. If you omit the third argument, the default is TWO_ SIDED_SIG. The meaning of the return values is shown in Table 5–5. The one-tailed significance is always in relation to the upper tail. The final argument, expr3, indicates which of the two groups specified by expr1 is the high value or numerator (the value whose rejection region is the upper tail). The observed value of f is the ratio of the variance of one group to the variance of the second group. The significance of the observed value of f is the probability that the variances are different just by chance--a number between 0 and 1. A small value for the significance indicates that the variances are significantly different. The degree of freedom for each of the variances is the number of observations in the sample minus 1. STATS_F_TEST Example The following example determines whether the variance in credit limit between men and women is significantly different. The results, a p_value not close to zero, and an f_statistic close to 1, indicate that the difference between credit limits for men and women are not significant. SELECT VARIANCE(DECODE(cust_gender, 'M', cust_credit_limit, null)) var_men, VARIANCE(DECODE(cust_gender, 'F', cust_credit_limit, null)) var_women, STATS_F_TEST(cust_gender, cust_credit_limit, 'STATISTIC', 'F') f_statistic, STATS_F_TEST(cust_gender, cust_credit_limit) two_sided_p_value FROM sh.customers; VAR_MEN VAR_WOMEN F_STATISTIC TWO_SIDED_P_VALUE ---------- ---------- ----------- ----------------- 12879896.7 13046865 1.01296348 .311928071 STATS_KS_TEST Syntax Purpose STATS_KS_TEST is a Kolmogorov-Smirnov function that compares two samples to test whether they are from the same population or from populations that have the same distribution. It does not assume that the population from which the samples were taken is normally distributed. Table 5–5 STATS_F_TEST Return Values Return Value Meaning STATISTIC The observed value of f DF_NUM Degree of freedom for the numerator DF_DEN Degree of freedom for the denominator ONE_SIDED_SIG One-tailed significance of f TWO_SIDED_SIG Two-tailed significance of f STATS_KS_TEST ( expr1 , expr2 , STATISTIC SIG )
- 324. STATS_MODE 5-162 Oracle Database SQL Reference This function takes three arguments: two expressions and a return value of type VARCHAR2. expr1 classifies the data into the two samples. expr2 contains the values for each of the samples. If expr1 classifies the rows into only one sample or into more than two samples, then an error is raised.The function returns one value determined by the third argument. If you omit the third argument, then the default is SIG. The meaning of the return values is shown in Table 5–6. STATS_KS_TEST Example Using the Kolmogorov Smirnov test, the following example determines whether the distribution of sales between men and women is due to chance: SELECT stats_ks_test(cust_gender, amount_sold, 'STATISTIC') ks_statistic, stats_ks_test(cust_gender, amount_sold) p_value FROM sh.customers c, sh.sales s WHERE c.cust_id = s.cust_id; KS_STATISTIC P_VALUE ------------ ---------- .003841396 .004080006 STATS_MODE Syntax Purpose STATS_MODE takes as its argument a set of values and returns the value that occurs with the greatest frequency. If more than one mode exists, Oracle Database chooses one and returns only that one value. To obtain multiple modes (if multiple modes exist), you must use a combination of other functions, as shown in the hypothetical query: SELECT x FROM (SELECT x, COUNT(x) AS cnt1 FROM t GROUP BY x) WHERE cnt1 = (SELECT MAX(cnt2) FROM (SELECT COUNT(x) AS cnt2 FROM t GROUP BY x)); Examples The following example returns the mode of salary per department in the hr.employees table: SELECT department_id, STATS_MODE(salary) FROM employees GROUP BY department_id; DEPARTMENT_ID STATS_MODE(SALARY) ------------- ------------------ 10 4400 Table 5–6 STATS_KS_TEST Return Values Return Value Meaning STATISTIC Observed value of D SIG Significance of D STATS_MODE ( expr )
- 325. STATS_MW_TEST Functions 5-163 20 6000 30 2500 40 6500 50 2500 60 4800 70 10000 80 9500 90 17000 100 6900 110 8300 7000 If you need to retrieve all of the modes (in cases with multiple modes), you can do so using a combination of other functions, as shown in the next example: SELECT commission_pct FROM (SELECT commission_pct, COUNT(commission_pct) AS cnt1 FROM employees GROUP BY commission_pct) WHERE cnt1 = (SELECT MAX (cnt2) FROM (SELECT COUNT(commission_pct) AS cnt2 FROM employees GROUP BY commission_pct)); COMMISSION_PCT -------------- .2 .3 STATS_MW_TEST Syntax Purpose A Mann Whitney test compares two independent samples to test the null hypothesis that two populations have the same distribution function against the alternative hypothesis that the two distribution functions are different. The STATS_MW_TEST does not assume that the differences between the samples are normally distributed, as do the STATS_T_TEST_* functions. This function takes three arguments and a return value of type VARCHAR2. expr1 classifies the data into groups. expr2 contains the values for each of the groups. The function returns one value, determined by the third argument. If you omit the third argument, the default is TWO_SIDED_SIG. The meaning of the return values is shown in the table that follows. The significance of the observed value of Z or U is the probability that the variances are different just by chance--a number between 0 and 1. A small value for the significance indicates that the variances are significantly different. The degree of freedom for each of the variances is the number of observations in the sample minus 1. STATS_MW_TEST ( expr1 , expr2 , STATISTIC U_STATISTIC ONE_SIDED_SIG expr3 TWO_SIDED_SIG )
- 326. STATS_ONE_WAY_ANOVA 5-164 Oracle Database SQL Reference The one-tailed significance is always in relation to the upper tail. The final argument, expr3, indicates which of the two groups specified by expr1 is the high value (the value whose rejection region is the upper tail). STATS_MW_TEST computes the probability that the samples are from the same distribution by checking the differences in the sums of the ranks of the values. If the samples come from the same distribution, then the sums should be close in value. STATS_MW_TEST Example Using the Mann Whitney test, the following example determines whether the distribution of sales between men and women is due to chance: SELECT STATS_MW_TEST (cust_gender, amount_sold, 'STATISTIC') z_statistic, STATS_MW_TEST (cust_gender, amount_sold, 'ONE_SIDED_SIG', 'F') one_sided_p_value FROM sh.customers c, sh.sales s WHERE c.cust_id = s.cust_id; Z_STATISTIC ONE_SIDED_P_VALUE ----------- ----------------- -1.4011509 .080584471 STATS_ONE_WAY_ANOVA Syntax Purpose The one-way analysis of variance function (STATS_ONE_WAY_ANOVA) tests differences in means (for groups or variables) for statistical significance by comparing two different estimates of variance. One estimate is based on the variances within each group or category. This is known as the mean squares within or mean square error. Table 5–7 STATS_MW_TEST Return Values Return Value Meaning STATISTIC The observed value of Z U_STATISTIC The observed value of U ONE_SIDED_SIG One-tailed significance of Z TWO_SIDED_SIG Two-tailed significance of Z STATS_ONE_WAY_ANOVA ( expr1 , expr2 , SUM_SQUARES_BETWEEN SUM_SQUARES_WITHIN DF_BETWEEN DF_WITHIN MEAN_SQUARES_BETWEEN MEAN_SQUARES_WITHIN F_RATIO SIG )
- 327. STATS_ONE_WAY_ANOVA Functions 5-165 The other estimate is based on the variances among the means of the groups. This is known as the mean squares between. If the means of the groups are significantly different, then the mean squares between will be larger than expected and will not match the mean squares within. If the mean squares of the groups are consistent, then the two variance estimates will be about the same. STATS_ONE_WAY_ANOVA takes three arguments: two expressions and a return value of type VARCHAR2. expr1 is an independent or grouping variable that divides the data into a set of groups. expr2 is a dependent variable (a numeric expression) containing the values corresponding to each member of a group. The function returns one number, determined by the value of the third argument. If you omit the third argument, the default is SIG. The meaning of the return values is shown in Table 5–8. The significance of one-way analysis of variance is determined by obtaining the one-tailed significance of an f-test on the ratio of the mean squares between and the mean squares within. The f-test should use one-tailed significance, because the mean squares between can be only equal to or larger than the mean squares within. Therefore, the significance returned by STATS_ONE_WAY_ANOVA is the probability that the differences between the groups happened by chance--a number between 0 and 1. The smaller the number, the greater the significance of the difference between the groups. Please refer to the STATS_F_TEST on page 5-161 for information on performing an f-test. STATS_ONE_WAY_ANOVA Example The following example determines the significance of the differences in mean sales within an income level and differences in mean sales between income levels. The results, p_values close to zero, indicate that, for both men and women, the difference in the amount of goods sold across different income levels is significant. SELECT cust_gender, STATS_ONE_WAY_ANOVA(cust_income_level, amount_sold, 'F_RATIO') f_ratio, STATS_ONE_WAY_ANOVA(cust_income_level, amount_sold, 'SIG') p_value FROM sh.customers c, sh.sales s WHERE c.cust_id = s.cust_id GROUP BY cust_gender; C F_RATIO P_VALUE - ---------- ---------- F 5.59536943 4.7840E-09 M 9.2865001 6.7139E-17 Table 5–8 STATS_ONE_WAY_ANOVA Return Values Return Value Meaning SUM_SQUARES_BETEEN Sum of squares between groups SUM_SQUARES_WITHIN Sum of squares within groups DF_BETWEEN Degree of freedom between groups DF_WITHIN Degree of freedom within groups MEAN_SQUARES_BETWEEN Mean squares between groups MEAN_SQUARES_WITHIN Mean squares within groups F_RATIO Ratio of the mean squares between to the mean squares within (MSB/MSW) SIG Significance
- 328. STATS_T_TEST_* 5-166 Oracle Database SQL Reference STATS_T_TEST_* The t-test functions are: ■ STATS_T_TEST_ONE: A one-sample t-test ■ STATS_T_TEST_PAIRED: A two-sample, paired t-test (also known as a crossed t-test) ■ STATS_T_TEST_INDEP: A t-test of two independent groups with the same variance (pooled variances) ■ STATS_T_TEST_INDEPU: A t-test of two independent groups with unequal variance (unpooled variances) Syntax stats_t_test::= Purpose The t-test measures the significance of a difference of means. You can use it to compare the means of two groups or the means of one group with a constant. The one-sample and two-sample STATS_T_TEST_* functions take three arguments: two expressions and a return value of type VARCHAR2. The functions return one number, determined by the value of the third argument. If you omit the third argument, the default is TWO_ SIDED_SIG. The meaning of the return values is shown in Table 5–9. The two independent STATS_T_TEST_* functions can take a fourth argument (expr3) if the third argument is specified as STATISTIC or ONE_SIDED_SIG. In this case, expr3 indicates which value of expr1 is the high value, or the value whose rejection region is the upper tail. The significance of the observed value of t is the probability that the value of t would have been obtained by chance--a number between 0 and 1. The smaller the value, the more significant the difference between the means. One-sided significance is always respect to the upper tail. For one-sample and paired t-test, the high value is the first expression. For independent t-test, the high value is the one specified by expr3. Table 5–9 STATS_T_TEST_* Return Values Return Value Meaning STATISTIC The observed value of t DF Degree of freedom ONE_SIDED_SIG One-tailed significance of t TWO_SIDED_SIG Two-tailed significance of t STATS_T_TEST_INDEP STATS_T_TEST_INDEPU STATS_T_TEST_ONE STATS_T_TEST_PAIRED ( expr1 , expr2 , STATISTIC ONE_SIDED_SIG expr3 TWO_SIDED_SIG DF )
- 329. STATS_T_TEST_* Functions 5-167 The degree of freedom depends on the type of t-test that resulted in the observed value of t. For example, for a one-sample t-test (STATS_T_TEST_ONE), the degree of freedom is the number of observations in the sample minus 1. STATS_T_TEST_ONE In the STATS_T_TEST_ONE function, expr1 is the sample and expr2 is the constant mean against which the sample mean is compared. For this t-test only, expr2 is optional; the constant mean defaults to 0. This function obtains the value of t by dividing the difference between the sample mean and the known mean by the standard error of the mean (rather than the standard error of the difference of the means, as for STATS_T_TEST_PAIRED). STATS_T_TEST_ONE Example The following example determines the significance of the difference between the average list price and the constant value 60: SELECT AVG(prod_list_price) group_mean, STATS_T_TEST_ONE(prod_list_price, 60, 'STATISTIC') t_observed, STATS_T_TEST_ONE(prod_list_price, 60) two_sided_p_value FROM sh.products; GROUP_MEAN T_OBSERVED TWO_SIDED_P_VALUE ---------- ---------- ----------------- 139.545556 2.32107746 .023158537 STATS_T_TEST_PAIRED In the STATS_T_TEST_PAIRED function, expr1 and expr2 are the two samples whose means are being compared. This function obtains the value of t by dividing the difference between the sample means by the standard error of the difference of the means (rather than the standard error of the mean, as for STATS_T_TEST_ONE). STATS_T_TEST_INDEP and STATS_T_TEST_INDEPU In the STATS_T_TEST_INDEP and STATS_T_TEST_INDEPU functions, expr1 is the grouping column and expr2 is the sample of values. The pooled variances version (STATS_T_TEST_INDEP) tests whether the means are the same or different for two distributions that have similar variances. The unpooled variances version (STATS_T_ TEST_INDEPU) tests whether the means are the same or different even if the two distributions are known to have significantly different variances. Before using these functions, it is advisable to determine whether the variances of the samples are significantly different. If they are, then the data may come from distributions with different shapes, and the difference of the means may not be very useful. You can perform an f-test to determine the difference of the variances. If they are not significantly different, use STATS_T_TEST_INDEP. If they are significantly different, use STATS_T_TEST_INDEPU. Please refer to STATS_F_TEST on page 5-161 for information on performing an f-test. STATS_T_TEST_INDEP Example The following example determines the significance of the difference between the average sales to men and women where the distributions are assumed to have similar (pooled) variances: SELECT SUBSTR(cust_income_level, 1, 22) income_level, AVG(DECODE(cust_gender, 'M', amount_sold, null)) sold_to_men, AVG(DECODE(cust_gender, 'F', amount_sold, null)) sold_to_women, STATS_T_TEST_INDEP(cust_gender, amount_sold, 'STATISTIC', 'F') t_observed, STATS_T_TEST_INDEP(cust_gender, amount_sold) two_sided_p_value
- 330. STATS_T_TEST_INDEP and STATS_T_TEST_INDEPU 5-168 Oracle Database SQL Reference FROM sh.customers c, sh.sales s WHERE c.cust_id = s.cust_id GROUP BY ROLLUP(cust_income_level); INCOME_LEVEL SOLD_TO_MEN SOLD_TO_WOMEN T_OBSERVED TWO_SIDED_P_VALUE ---------------------- ----------- ------------- ---------- ----------------- A: Below 30,000 105.28349 99.4281447 -1.9880629 .046811482 B: 30,000 - 49,999 102.59651 109.829642 3.04330875 .002341053 C: 50,000 - 69,999 105.627588 110.127931 2.36148671 .018204221 D: 70,000 - 89,999 106.630299 110.47287 2.28496443 .022316997 E: 90,000 - 109,999 103.396741 101.610416 -1.2544577 .209677823 F: 110,000 - 129,999 106.76476 105.981312 -.60444998 .545545304 G: 130,000 - 149,999 108.877532 107.31377 -.85298245 .393671218 H: 150,000 - 169,999 110.987258 107.152191 -1.9062363 .056622983 I: 170,000 - 189,999 102.808238 107.43556 2.18477851 .028908566 J: 190,000 - 249,999 108.040564 115.343356 2.58313425 .009794516 K: 250,000 - 299,999 112.377993 108.196097 -1.4107871 .158316973 L: 300,000 and above 120.970235 112.216342 -2.0642868 .039003862 107.121845 113.80441 .686144393 .492670059 106.663769 107.276386 1.08013499 .280082357 14 rows selected. STATS_T_TEST_INDEPU Example The following example determines the significance of the difference between the average sales to men and women where the distributions are known to have significantly different (unpooled) variances: SELECT SUBSTR(cust_income_level, 1, 22) income_level, AVG(DECODE(cust_gender, 'M', amount_sold, null)) sold_to_men, AVG(DECODE(cust_gender, 'F', amount_sold, null)) sold_to_women, STATS_T_TEST_INDEPU(cust_gender, amount_sold, 'STATISTIC', 'F') t_observed, STATS_T_TEST_INDEPU(cust_gender, amount_sold) two_sided_p_value FROM sh.customers c, sh.sales s WHERE c.cust_id = s.cust_id GROUP BY ROLLUP(cust_income_level); INCOME_LEVEL SOLD_TO_MEN SOLD_TO_WOMEN T_OBSERVED TWO_SIDED_P_VALUE ---------------------- ----------- ------------- ---------- ----------------- A: Below 30,000 105.28349 99.4281447 -2.0542592 .039964704 B: 30,000 - 49,999 102.59651 109.829642 2.96922332 .002987742 C: 50,000 - 69,999 105.627588 110.127931 2.3496854 .018792277 D: 70,000 - 89,999 106.630299 110.47287 2.26839281 .023307831 E: 90,000 - 109,999 103.396741 101.610416 -1.2603509 .207545662 F: 110,000 - 129,999 106.76476 105.981312 -.60580011 .544648553 G: 130,000 - 149,999 108.877532 107.31377 -.85219781 .394107755 H: 150,000 - 169,999 110.987258 107.152191 -1.9451486 .051762624 I: 170,000 - 189,999 102.808238 107.43556 2.14966921 .031587875 J: 190,000 - 249,999 108.040564 115.343356 2.54749867 .010854966 K: 250,000 - 299,999 112.377993 108.196097 -1.4115514 .158091676 L: 300,000 and above 120.970235 112.216342 -2.0726194 .038225611 107.121845 113.80441 .689462437 .490595765 106.663769 107.276386 1.07853782 .280794207 14 rows selected.
- 331. STDDEV Functions 5-169 STATS_WSR_TEST Syntax Purpose STATS_WSR_TEST is a Wilcoxon Signed Ranks test of paired samples to determine whether the median of the differences between the samples is significantly different from zero. The absolute values of the differences are ordered and assigned ranks. Then the null hypothesis states that the sum of the ranks of the positive differences is equal to the sum of the ranks of the negative differences. This function takes three arguments: expr1 and expr2 are the two samples being analyzed, and the third argument is a return value of type VARCHAR2. If you omit the third argument, the default is TWO_SIDED_SIG. The meaning of the return values is shown in Table 5–10. One-sided significance is always with respect to the upper tail. The high value—that is, the value whose rejection region is the upper tail—is expr1. STDDEV Syntax Purpose STDDEV returns the sample standard deviation of expr, a set of numbers. You can use it as both an aggregate and analytic function. It differs from STDDEV_SAMP in that STDDEV returns zero when it has only 1 row of input data, whereas STDDEV_SAMP returns null. Oracle Database calculates the standard deviation as the square root of the variance defined for the VARIANCE aggregate function. Table 5–10 STATS_WSR_TEST_* Return Values Return Value Meaning STATISTIC The observed value of Z ONE_SIDED_SIG One-tailed significance of Z TWO_SIDED_SIG Two-tailed significance of Z See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions STATS_WSR_TEST ( expr1 , expr2 , STATISTIC ONE_SIDED_SIG TWO_SIDED_SIG ) STDDEV ( DISTINCT ALL expr ) OVER ( analytic_clause )
- 332. STDDEV_POP 5-170 Oracle Database SQL Reference This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument. If you specify DISTINCT, then you can specify only the query_partition_clause of the analytic_clause. The order_by_clause and windowing_clause are not allowed. Aggregate Examples The following example returns the standard deviation of the salaries in the sample hr.employees table: SELECT STDDEV(salary) "Deviation" FROM employees; Deviation ---------- 3909.36575 Analytic Examples The query in the following example returns the cumulative standard deviation of the salaries in Department 80 in the sample table hr.employees, ordered by hire_ date: SELECT last_name, salary, STDDEV(salary) OVER (ORDER BY hire_date) "StdDev" FROM employees WHERE department_id = 30; LAST_NAME SALARY StdDev ------------------------- ---------- ---------- Raphaely 11000 0 Khoo 3100 5586.14357 Tobias 2800 4650.0896 Baida 2900 4035.26125 Himuro 2600 3649.2465 Colmenares 2500 3362.58829 STDDEV_POP Syntax See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion See Also: ■ "Aggregate Functions" on page 5-8, VARIANCE on page 5-216, and STDDEV_SAMP on page 5-172 ■ "About SQL Expressions" on page 6-1 for information on valid forms of expr STDDEV_POP ( expr ) OVER ( analytic_clause )
- 333. STDDEV_POP Functions 5-171 Purpose STDDEV_POP computes the population standard deviation and returns the square root of the population variance. You can use it as both an aggregate and analytic function. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument. This function is the same as the square root of the VAR_POP function. When VAR_POP returns null, this function returns null. Aggregate Example The following example returns the population and sample standard deviations of the amount of sales in the sample table sh.sales: SELECT STDDEV_POP(amount_sold) "Pop", STDDEV_SAMP(amount_sold) "Samp" FROM sales; Pop Samp ---------- ---------- 896.355151 896.355592 Analytic Example The following example returns the population standard deviations of salaries in the sample hr.employees table by department: SELECT department_id, last_name, salary, STDDEV_POP(salary) OVER (PARTITION BY department_id) AS pop_std FROM employees; DEPARTMENT_ID LAST_NAME SALARY POP_STD ------------- ------------------------- ---------- ---------- 10 Whalen 4400 0 20 Hartstein 13000 3500 20 Goyal 6000 3500 . . . 100 Sciarra 7700 1644.18166 100 Urman 7800 1644.18166 100 Popp 6900 1644.18166 110 Higgens 12000 1850 110 Gietz 8300 1850 See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion See Also: ■ "Aggregate Functions" on page 5-8 and VAR_POP on page 5-214 ■ "About SQL Expressions" on page 6-1 for information on valid forms of expr
- 334. STDDEV_SAMP 5-172 Oracle Database SQL Reference STDDEV_SAMP Syntax Purpose STDDEV_SAMP computes the cumulative sample standard deviation and returns the square root of the sample variance. You can use it as both an aggregate and analytic function. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument. This function is same as the square root of the VAR_SAMP function. When VAR_SAMP returns null, this function returns null. Aggregate Example Please refer to the aggregate example for STDDEV_POP on page 5-171. Analytic Example The following example returns the sample standard deviation of salaries in the employees table by department: SELECT department_id, last_name, hire_date, salary, STDDEV_SAMP(salary) OVER (PARTITION BY department_id ORDER BY hire_date ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS cum_sdev FROM employees; DEPARTMENT_ID LAST_NAME HIRE_DATE SALARY CUM_SDEV ------------- --------------- --------- ---------- ---------- 10 Whalen 17-SEP-87 4400 20 Hartstein 17-FEB-96 13000 20 Goyal 17-AUG-97 6000 4949.74747 30 Raphaely 07-DEC-94 11000 30 Khoo 18-MAY-95 3100 5586.14357 30 Tobias 24-JUL-97 2800 4650.0896 30 Baida 24-DEC-97 2900 4035.26125 . . . 100 Chen 28-SEP-97 8200 2003.33056 100 Sciarra 30-SEP-97 7700 1925.91969 See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion See Also: ■ "Aggregate Functions" on page 5-8 and VAR_SAMP on page 5-216 ■ "About SQL Expressions" on page 6-1 for information on valid forms of expr STDDEV_SAMP ( expr ) OVER ( analytic_clause )
- 335. SUBSTR Functions 5-173 100 Urman 07-MAR-98 7800 1785.49713 100 Popp 07-DEC-99 6900 1801.11077 110 Higgens 07-JUN-94 12000 110 Gietz 07-JUN-94 8300 2616.29509 SUBSTR Syntax substr::= Purpose The SUBSTR functions return a portion of char, beginning at character position, substring_length characters long. SUBSTR calculates lengths using characters as defined by the input character set. SUBSTRB uses bytes instead of characters. SUBSTRC uses Unicode complete characters. SUBSTR2 uses UCS2 code points. SUBSTR4 uses UCS4 code points. ■ If position is 0, then it is treated as 1. ■ If position is positive, then Oracle Database counts from the beginning of char to find the first character. ■ If position is negative, then Oracle counts backward from the end of char. ■ If substring_length is omitted, then Oracle returns all characters to the end of char. If substring_length is less than 1, then Oracle returns null. char can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. Both position and substring_length must be of datatype NUMBER, or any datatype that can be implicitly converted to NUMBER, and must resolve to an integer. The return value is the same datatype as char. Floating-point numbers passed as arguments to SUBSTR are automatically converted to integers. Examples The following example returns several specified substrings of "ABCDEFG": SELECT SUBSTR('ABCDEFG',3,4) "Substring" FROM DUAL; Substring --------- CDEF SELECT SUBSTR('ABCDEFG',-5,4) "Substring" See Also: Oracle Database Globalization Support Guide for more information about SUBSTR functions and length semantics in different locales SUBSTR SUBSTRB SUBSTRC SUBSTR2 SUBSTR4 ( char , position , substring_length )
- 336. SUM 5-174 Oracle Database SQL Reference FROM DUAL; Substring --------- CDEF Assume a double-byte database character set: SELECT SUBSTRB('ABCDEFG',5,4.2) "Substring with bytes" FROM DUAL; Substring with bytes -------------------- CD SUM Syntax Purpose SUM returns the sum of values of expr. You can use it as an aggregate or analytic function. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument. If you specify DISTINCT, then you can specify only the query_partition_clause of the analytic_clause. The order_by_clause and windowing_clause are not allowed. Aggregate Example The following example calculates the sum of all salaries in the sample hr.employees table: SELECT SUM(salary) "Total" FROM employees; Total ---------- 691400 See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion See Also: "About SQL Expressions" on page 6-1 for information on valid forms of expr and "Aggregate Functions" on page 5-8 SUM ( DISTINCT ALL expr ) OVER ( analytic_clause )
- 337. SYS_CONNECT_BY_PATH Functions 5-175 Analytic Example The following example calculates, for each manager in the sample table hr.employees, a cumulative total of salaries of employees who answer to that manager that are equal to or less than the current salary. You can see that Raphaely and Cambrault have the same cumulative total. This is because Raphaely and Cambrault have the identical salaries, so Oracle Database adds together their salary values and applies the same cumulative total to both rows. SELECT manager_id, last_name, salary, SUM(salary) OVER (PARTITION BY manager_id ORDER BY salary RANGE UNBOUNDED PRECEDING) l_csum FROM employees; MANAGER_ID LAST_NAME SALARY L_CSUM ---------- --------------- ---------- ---------- 100 Mourgos 5800 5800 100 Vollman 6500 12300 100 Kaufling 7900 20200 100 Weiss 8000 28200 100 Fripp 8200 36400 100 Zlotkey 10500 46900 100 Raphaely 11000 68900 100 Cambrault 11000 68900 100 Errazuriz 12000 80900 . . . 149 Taylor 8600 30200 149 Hutton 8800 39000 149 Abel 11000 50000 201 Fay 6000 6000 205 Gietz 8300 8300 King 24000 24000 SYS_CONNECT_BY_PATH Syntax Purpose SYS_CONNECT_BY_PATH is valid only in hierarchical queries. It returns the path of a column value from root to node, with column values separated by char for each row returned by CONNECT BY condition. Both column and char can be any of the datatypes CHAR, VARCHAR2, NCHAR, or NVARCHAR2. The string returned is of VARCHAR2 datatype and is in the same character set as column. Examples The following example returns the path of employee names from employee Kochhar to all employees of Kochhar (and their employees): SELECT LPAD(' ', 2*level-1)||SYS_CONNECT_BY_PATH(last_name, '/') "Path" FROM employees START WITH last_name = 'Kochhar' See Also: "Hierarchical Queries" on page 9-2 for more information about hierarchical queries and CONNECT BY conditions SYS_CONNECT_BY_PATH ( column , char )
- 338. SYS_CONTEXT 5-176 Oracle Database SQL Reference CONNECT BY PRIOR employee_id = manager_id; Path --------------------------------------------------------------- /Kochhar /Kochhar/Greenberg /Kochhar/Greenberg/Faviet /Kochhar/Greenberg/Chen /Kochhar/Greenberg/Sciarra /Kochhar/Greenberg/Urman /Kochhar/Greenberg/Popp /Kochhar/Whalen /Kochhar/Mavris /Kochhar/Baer /Kochhar/Higgins /Kochhar/Higgins/Gietz SYS_CONTEXT Syntax Purpose SYS_CONTEXT returns the value of parameter associated with the context namespace. You can use this function in both SQL and PL/SQL statements. For namespace and parameter, you can specify either a string or an expression that resolves to a string designating a namespace or an attribute. The context namespace must already have been created, and the associated parameter and its value must also have been set using the DBMS_SESSION.set_context procedure. The namespace must be a valid SQL identifier. The parameter name can be any string. It is not case sensitive, but it cannot exceed 30 bytes in length. The datatype of the return value is VARCHAR2. The default maximum size of the return value is 256 bytes. You can override this default by specifying the optional length parameter, which must be a NUMBER or a value that can be implicitly converted to NUMBER. The valid range of values is 1 to 4000 bytes. If you specify an invalid value, then Oracle Database ignores it and uses the default. Oracle provides a built-in namespace called USERENV, which describes the current session. The predefined parameters of namespace USERENV are listed in Table 5–11 on page 5-177. See Also: ■ Oracle Database Application Developer's Guide - Fundamentals for information on using the application context feature in your application development ■ CREATE CONTEXT on page 14-9 for information on creating user-defined context namespaces ■ Oracle Database PL/SQL Packages and Types Reference for information on the DBMS_SESSION.set_context procedure SYS_CONTEXT ( ’ namespace ’ , ’ parameter ’ , length )
- 339. SYS_CONTEXT Functions 5-177 Examples The following statement returns the name of the user who logged onto the database: CONNECT OE/OE SELECT SYS_CONTEXT ('USERENV', 'SESSION_USER') FROM DUAL; SYS_CONTEXT ('USERENV', 'SESSION_USER') ------------------------------------------------------ OE The following hypothetical example returns the group number that was set as the value for the attribute group_no in the PL/SQL package that was associated with the context hr_apps when hr_apps was created: SELECT SYS_CONTEXT ('hr_apps', 'group_no') "User Group" FROM DUAL; Table 5–11 Predefined Parameters of Namespace USERENV Parameter Return Value ACTION Identifies the position in the module (application name) and is set through the DBMS_APPLICATION_INFO package or OCI. AUDITED_CURSORID Returns the cursor ID of the SQL that triggered the audit. This parameter is not valid in a fine-grained auditing environment. If you specify it in such an environment, Oracle Database always returns NULL. AUTHENTICATED_ IDENTITY Returns the identity used in authentication. In the list that follows, the type of user is followed by the value returned: ■ Kerberos-authenticated enterprise user: kerberos principal name ■ Kerberos-authenticated external user : kerberos principal name; same as the schema name ■ SSL-authenticated enterprise user: the DN in the user’s PKI certificate ■ SSL-authenticated external user: the DN in the user's PKI certificate ■ Password-authenticated enterprise user: nickname; same as the login name ■ Password-authenticated database user: the database username; same as the schema name ■ OS-authenticated external user: the external operating system user name ■ Radius/DCE-authenticated external user: the schema name ■ Proxy with DN : Oracle Internet Directory DN of the client ■ Proxy with certificate: certificate DN of the client ■ Proxy with username: database user name if client is a local database user; nickname if client is an enterprise user. ■ SYSDBA/SYSOPER using Password File: login name ■ SYSDBA/SYSOPER using OS authentication: operating system user name AUTHENTICATION_DATA Data being used to authenticate the login user. For X.503 certificate authenticated sessions, this field returns the context of the certificate in HEX2 format. Note: You can change the return value of the AUTHENTICATION_DATA attribute using the length parameter of the syntax. Values of up to 4000 are accepted. This is the only attribute of USERENV for which Oracle Database implements such a change.
- 340. SYS_CONTEXT 5-178 Oracle Database SQL Reference AUTHENTICATION_ METHOD Returns the method of authentication. In the list that follows, the type of user is followed by the method returned: ■ Password-authenticated enterprise user, local database user, or SYSDBA/SYSOPER using Password File; proxy with username using password: PASSWORD ■ Kerberos-authenticated enterprise or external user: KERBEROS ■ SSL-authenticated enterprise or external user: SSL ■ Radius-authenticated external user: RADIUS ■ OS-authenticated external user or SYSDBA/SYSOPER: OS ■ DCE-authenticated external user: DCE ■ Proxy with certificate, DN, or username without using password: NONE You can use IDENTIFICATION_TYPE to distinguish between external and enterprise users when the authentication method is Password, Kerberos, or SSL. BG_JOB_ID Job ID of the current session if it was established by an Oracle Database background process. Null if the session was not established by a background process. CLIENT_IDENTIFIER Returns an identifier that is set by the application through the DBMS_ SESSION.SET_IDENTIFIER procedure, the OCI attribute OCI_ATTR_CLIENT_ IDENTIFIER, or the Java class Oracle.jdbc.OracleConnection.setClientIdentifier. This attribute is used by various database components to identify lightweight application users who authenticate as the same database user. CLIENT_INFO Returns up to 64 bytes of user session information that can be stored by an application using the DBMS_APPLICATION_INFO package. CURRENT_BIND The bind variables for fine-grained auditing. CURRENT_SCHEMA Name of the default schema being used in the current schema. This value can be changed during the session with an ALTER SESSION SET CURRENT_SCHEMA statement. CURRENT_SCHEMAID Identifier of the default schema being used in the current session. CURRENT_SQL CURRENT_SQLn CURRENT_SQL returns the first 4K bytes of the current SQL that triggered the fine-grained auditing event. The CURRENT_SQLn attributes return subsequent 4K-byte increments, where n can be an integer from 1 to 7, inclusive. CURRENT_ SQL1 returns bytes 4K to 8K; CURRENT_SQL2 returns bytes 8K to 12K, and so forth. You can specify these attributes only inside the event handler for the fine-grained auditing feature. CURRENT_SQL_LENGTH The length of the current SQL statement that triggers fine-grained audit or row-level security (RLS) policy functions or event handlers. Valid only inside the function or event handler. DB_DOMAIN Domain of the database as specified in the DB_DOMAIN initialization parameter. DB_NAME Name of the database as specified in the DB_NAME initialization parameter. DB_UNIQUE_NAME Name of the database as specified in the DB_UNIQUE_NAME initialization parameter. ENTRYID The current audit entry number. The audit entryid sequence is shared between fine-grained audit records and regular audit records. You cannot use this attribute in distributed SQL statements. The correct auditing entry identifier can be seen only through an audit handler for standard or fine-grained audit. Table 5–11 (Cont.) Predefined Parameters of Namespace USERENV Parameter Return Value
- 341. SYS_CONTEXT Functions 5-179 ENTERPRISE_IDENTITY Returns the user's enterprise-wide identity: ■ For enterprise users: the Oracle Internet Directory DN. ■ For external users: the external identity (Kerberos principal name, Radius and DCE schema names, OS user name, Certificate DN). ■ For local users and SYSDBA/SYSOPER logins: NULL. The value of the attribute differs by proxy method: ■ For a proxy with DN: the Oracle Internet Directory DN of the client ■ For a proxy with certificate: the certificate DN of the client for external users; the Oracle Internet Directory DN for global users ■ For a proxy with username: the Oracle Internet Directory DN if the client is an enterprise users; NULL if the client is a local database user. FG_JOB_ID Job ID of the current session if it was established by a client foreground process. Null if the session was not established by a foreground process. GLOBAL_CONTEXT_ MEMORY Returns the number being used in the System Global Area by the globally accessed context. GLOBAL_UID Returns the global user ID from Oracle Internet Directory for Enterprise User Security (EUS) logins; returns null for all other logins. HOST Name of the host machine from which the client has connected. IDENTIFICATION_TYPE Returns the way the user's schema was created in the database. Specifically, it reflects the IDENTIFIED clause in the CREATE/ALTER USER syntax. In the list that follows, the syntax used during schema creation is followed by the identification type returned: ■ IDENTIFIED BY password: LOCAL ■ IDENTIFIED EXTERNALLY: EXTERNAL ■ IDENTIFIED GLOBALLY: GLOBAL SHARED ■ IDENTIFIED GLOBALLY AS DN: GLOBAL PRIVATE INSTANCE The instance identification number of the current instance. INSTANCE_NAME The name of the instance. IP_ADDRESS IP address of the machine from which the client is connected. ISDBA Returns TRUE if the user has been authenticated as having DBA privileges either through the operating system or through a password file. LANG The ISO abbreviation for the language name, a shorter form than the existing 'LANGUAGE' parameter. LANGUAGE The language and territory currently used by your session, along with the database character set, in this form: language_territory.characterset MODULE The application name (module) set through the DBMS_APPLICATION_INFO package or OCI. NETWORK_PROTOCOL Network protocol being used for communication, as specified in the 'PROTOCOL=protocol' portion of the connect string. NLS_CALENDAR The current calendar of the current session. NLS_CURRENCY The currency of the current session. NLS_DATE_FORMAT The date format for the session. NLS_DATE_LANGUAGE The language used for expressing dates. Table 5–11 (Cont.) Predefined Parameters of Namespace USERENV Parameter Return Value
- 342. SYS_CONTEXT 5-180 Oracle Database SQL Reference Table 5–12 lists the parameters of namespace USERENV that have been deprecated. Oracle suggests that you use the alternatives suggested in the Comments column. NLS_SORT BINARY or the linguistic sort basis. NLS_TERRITORY The territory of the current session. OS_USER Operating system user name of the client process that initiated the database session. POLICY_INVOKER The invoker of row-level security (RLS) policy functions. PROXY_ENTERPRISE_ IDENTITY Returns the Oracle Internet Directory DN when the proxy user is an enterprise user. PROXY_GLOBAL_UID Returns the global user ID from Oracle Internet Directory for Enterprise User Security (EUS) proxy users; returns NULL for all other proxy users. PROXY_USER Name of the database user who opened the current session on behalf of SESSION_ USER. PROXY_USERID Identifier of the database user who opened the current session on behalf of SESSION_USER. SERVER_HOST The host name of the machine on which the instance is running. SERVICE_NAME The name of the service to which a given session is connected. SESSION_USER For enterprises users, returns the schema. For other users, returns the database user name by which the current user is authenticated. This value remains the same throughout the duration of the session. SESSION_USERID Identifier of the database user name by which the current user is authenticated. SESSIONID The auditing session identifier. You cannot use this attribute in distributed SQL statements. SID The session number (different from the session ID). STATEMENTID The auditing statement identifier. STATEMENTID represents the number of SQL statements audited in a given session. You cannot use this attribute in distributed SQL statements. The correct auditing statement identifier can be seen only through an audit handler for standard or fine-grained audit. TERMINAL The operating system identifier for the client of the current session. In distributed SQL statements, this attribute returns the identifier for your local session. In a distributed environment, this is supported only for remote SELECT statements, not for remote INSERT, UPDATE, or DELETE operations. (The return length of this parameter may vary by operating system.) Table 5–12 Deprecated Parameters of Namespace USERENV Parameter Comments AUTHENTICATION_TYPE This parameter returned a value indicating how the user was authenticated. The same information is now available from the new AUTHENTICATION_METHOD parameter combined with IDENTIFICATION_TYPE. CURRENT_USER Use the SESSION_USER parameter instead. CURRENT_USERID Use the SESSION_USERID parameter instead. EXTERNAL_NAME This parameter returned the external name of the user. More complete information can now be obtained from the AUTHENTICATED_IDENTITY and ENTERPRISE_ IDENTITY parameter. Table 5–11 (Cont.) Predefined Parameters of Namespace USERENV Parameter Return Value
- 343. SYS_EXTRACT_UTC Functions 5-181 SYS_DBURIGEN Syntax Purpose SYS_DBURIGen takes as its argument one or more columns or attributes, and optionally a rowid, and generates a URL of datatype DBURIType to a particular column or row object. You can then use the URL to retrieve an XML document from the database. All columns or attributes referenced must reside in the same table. They must perform the function of a primary key. That is, they need not actually match the primary key of the table, but they must reference a unique value. If you specify multiple columns, then all but the final column identify the row in the database, and the last column specified identifies the column within the row. By default the URL points to a formatted XML document. If you want the URL to point only to the text of the document, then specify the optional 'text()'. If the table or view containing the columns or attributes does not have a schema specified in the context of the query, then Oracle Database interprets the table or view name as a public synonym. Examples The following example uses the SYS_DBURIGen function to generate a URL of datatype DBURIType to the email column of the row in the sample table hr.employees where the employee_id = 206: SELECT SYS_DBURIGEN(employee_id, email) FROM employees WHERE employee_id = 206; SYS_DBURIGEN(EMPLOYEE_ID,EMAIL)(URL, SPARE) -------------------------------------------------------------------- DBURITYPE('/PUBLIC/EMPLOYEES/ROW[EMPLOYEE_ID=''206'']/EMAIL', NULL) SYS_EXTRACT_UTC Syntax Note: In this XML context, the lowercase text is a keyword, not a syntactic placeholder. See Also: Oracle XML Developer's Kit Programmer's Guide for information on the URIType datatype and XML documents in the database SYS_DBURIGEN ( column attribute rowid , , ’ text ( ) ’ ) SYS_EXTRACT_UTC ( datetime_with_timezone )
- 344. SYS_GUID 5-182 Oracle Database SQL Reference Purpose SYS_EXTRACT_UTC extracts the UTC (Coordinated Universal Time--formerly Greenwich Mean Time) from a datetime value with time zone offset or time zone region name. Examples The following example extracts the UTC from a specified datetime: SELECT SYS_EXTRACT_UTC(TIMESTAMP '2000-03-28 11:30:00.00 -08:00') FROM DUAL; SYS_EXTRACT_UTC(TIMESTAMP'2000-03-2811:30:00.00-08:00') ----------------------------------------------------------------- 28-MAR-00 07.30.00 PM SYS_GUID Syntax Purpose SYS_GUID generates and returns a globally unique identifier (RAW value) made up of 16 bytes. On most platforms, the generated identifier consists of a host identifier, a process or thread identifier of the process or thread invoking the function, and a nonrepeating value (sequence of bytes) for that process or thread. Examples The following example adds a column to the sample table hr.locations, inserts unique identifiers into each row, and returns the 32-character hexadecimal representation of the 16-byte RAW value of the global unique identifier: ALTER TABLE locations ADD (uid_col RAW(32)); UPDATE locations SET uid_col = SYS_GUID(); SELECT location_id, uid_col FROM locations; LOCATION_ID UID_COL ----------- ---------------------------------------- 1000 7CD5B7769DF75CEFE034080020825436 1100 7CD5B7769DF85CEFE034080020825436 1200 7CD5B7769DF95CEFE034080020825436 1300 7CD5B7769DFA5CEFE034080020825436 . . . SYS_TYPEID Syntax SYS_GUID ( ) SYS_TYPEID ( object_type_value )
- 345. SYS_XMLAGG Functions 5-183 Purpose SYS_TYPEID returns the typeid of the most specific type of the operand. This value is used primarily to identify the type-discriminant column underlying a substitutable column. For example, you can use the value returned by SYS_TYPEID to build an index on the type-discriminant column. You can use this function only on object type operands. All final root object types--that is, final types not belonging to a type hierarchy--have a null typeid. Oracle Database assigns to all types belonging to a type hierarchy a unique non-null typeid. Examples The following examples use the tables persons and books, which are created in "Substitutable Table and Column Examples" on page 16-51. Both tables in turn use the person_t type, which is created in "Type Hierarchy Example" on page 17-17. The first query returns the most specific types of the object instances stored in the persons table. SELECT name, SYS_TYPEID(VALUE(p)) "Type_id" FROM persons p; NAME Type_id ------------------------- -------------------------------- Bob 01 Joe 02 Tim 03 The next query returns the most specific types of authors stored in the table books: SELECT b.title, b.author.name, SYS_TYPEID(author) "Type_ID" FROM books b; TITLE AUTHOR.NAME Type_ID ------------------------- -------------------- ------------------- An Autobiography Bob 01 Business Rules Joe 02 Mixing School and Work Tim 03 You can use the SYS_TYPEID function to create an index on the type-discriminant column of a table. For an example, see "Indexing on Substitutable Columns: Examples" on page 14-79. SYS_XMLAGG Syntax Purpose SYS_XMLAgg aggregates all of the XML documents or fragments represented by expr and produces a single XML document. It adds a new enclosing element with a default name ROWSET. If you want to format the XML document differently, then specify fmt, which is an instance of the XMLFormat object. See Also: Oracle Database Application Developer's Guide - Object-Relational Features for more information on typeids SYS_XMLAGG ( expr , fmt )
- 346. SYS_XMLGEN 5-184 Oracle Database SQL Reference Examples The following example uses the SYS_XMLGen function to generate an XML document for each row of the sample table employees where the employee's last name begins with the letter R, and then aggregates all of the rows into a single XML document in the default enclosing element ROWSET: SELECT SYS_XMLAGG(SYS_XMLGEN(last_name)) FROM employees WHERE last_name LIKE 'R%'; SYS_XMLAGG(SYS_XMLGEN(LAST_NAME)) -------------------------------------------------------------------- <ROWSET> <LAST_NAME>Raphaely</LAST_NAME> <LAST_NAME>Rogers</LAST_NAME> <LAST_NAME>Rajs</LAST_NAME> <LAST_NAME>Russell</LAST_NAME> </ROWSET> SYS_XMLGEN Syntax Purpose SYS_XMLGen takes an expression that evaluates to a particular row and column of the database, and returns an instance of type XMLType containing an XML document. The expr can be a scalar value, a user-defined type, or an XMLType instance. ■ If expr is a scalar value, then the function returns an XML element containing the scalar value. ■ If expr is a type, then the function maps the user-defined type attributes to XML elements. ■ If expr is an XMLType instance, then the function encloses the document in an XML element whose default tag name is ROW. By default the elements of the XML document match the elements of expr. For example, if expr resolves to a column name, then the enclosing XML element will be the same column name. If you want to format the XML document differently, then specify fmt, which is an instance of the XMLFormat object. See Also: ■ SYS_XMLGEN on page 5-185 and "XML Format Model" on page 2-67 for using the attributes of the XMLFormat type to format SYS_XMLAgg results ■ Oracle Database Concepts and Oracle XML Developer's Kit Programmer's Guide for information on XML types and their use SYS_XMLGEN ( expr , fmt )
- 347. SYSTIMESTAMP Functions 5-185 Examples The following example retrieves the employee email ID from the sample table oe.employees where the employee_id value is 205, and generates an instance of an XMLType containing an XML document with an EMAIL element. SELECT SYS_XMLGEN(email) FROM employees WHERE employee_id = 205; SYS_XMLGEN(EMAIL) ------------------------------------------------------------------- <EMAIL>SHIGGINS</EMAIL> SYSDATE Syntax Purpose SYSDATE returns the current date and time set for the operating system on which the database resides. The datatype of the returned value is DATE, and the format returned depends on the value of the NLS_DATE_FORMAT initialization parameter. The function requires no arguments. In distributed SQL statements, this function returns the date and time set for the operating system of your local database. You cannot use this function in the condition of a CHECK constraint. Examples The following example returns the current operating system date and time: SELECT TO_CHAR (SYSDATE, 'MM-DD-YYYY HH24:MI:SS') "NOW" FROM DUAL; NOW ------------------- 04-13-2001 09:45:51 SYSTIMESTAMP Syntax See Also: ■ "XML Format Model" on page 2-67 for a description of the XMLFormat type and how to use its attributes to format SYS_ XMLGen results ■ Oracle Database Concepts and Oracle XML Developer's Kit Programmer's Guide for information on XML types and their use SYSDATE SYSTIMESTAMP
- 348. TAN 5-186 Oracle Database SQL Reference Purpose SYSTIMESTAMP returns the system date, including fractional seconds and time zone, of the system on which the database resides. The return type is TIMESTAMP WITH TIME ZONE. Examples The following example returns the system timestamp: SELECT SYSTIMESTAMP FROM DUAL; SYSTIMESTAMP ------------------------------------------------------------------ 28-MAR-00 12.38.55.538741 PM -08:00 The following example shows how to explicitly specify fractional seconds: SELECT TO_CHAR(SYSTIMESTAMP, 'SSSSS.FF') FROM DUAL; TO_CHAR(SYSTIME --------------- 55615.449255 TAN Syntax Purpose TAN returns the tangent of n (an angle expressed in radians). This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. If the argument is BINARY_ FLOAT, then the function returns BINARY_DOUBLE. Otherwise the function returns the same numeric datatype as the argument. Examples The following example returns the tangent of 135 degrees: SELECT TAN(135 * 3.14159265359/180) "Tangent of 135 degrees" FROM DUAL; Tangent of 135 degrees ---------------------- - 1 TANH Syntax See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion TAN ( n ) TANH ( n )
- 349. TIMESTAMP_TO_SCN Functions 5-187 Purpose TANH returns the hyperbolic tangent of n. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. If the argument is BINARY_ FLOAT, then the function returns BINARY_DOUBLE. Otherwise the function returns the same numeric datatype as the argument. Examples The following example returns the hyperbolic tangent of .5: SELECT TANH(.5) "Hyperbolic tangent of .5" FROM DUAL; Hyperbolic tangent of .5 ------------------------ .462117157 TIMESTAMP_TO_SCN Syntax Purpose TIMESTAMP_TO_SCN takes as an argument a timestamp value and returns the approximate system change number (SCN) associated with that timestamp. The returned value is of datatype NUMBER. This function is useful any time you want to know the SCN associated with a particular timestamp. Examples The following example inserts a row into the oe.orders table and then uses TIMESTAMP_TO_SCN to determine the system change number of the insert operation. (The actual SCN returned will differ on each system.) INSERT INTO orders (order_id, order_date, customer_id, order_total) VALUES (5000, SYSTIMESTAMP, 188, 2345); 1 row created. COMMIT; Commit complete. SELECT TIMESTAMP_TO_SCN(order_date) FROM orders WHERE order_id = 5000; TIMESTAMP_TO_SCN(ORDER_DATE) ---------------------------- 574100 See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion See Also: SCN_TO_TIMESTAMP on page 5-153 for information on converting SCNs to timestamp TIMESTAMP_TO_SCN ( timestamp )
- 350. TO_BINARY_DOUBLE 5-188 Oracle Database SQL Reference TO_BINARY_DOUBLE Syntax Purpose TO_BINARY_DOUBLE returns a double-precision floating-point number. ■ expr can be a character string or a numeric value of type NUMBER, BINARY_ FLOAT, or BINARY_DOUBLE. If expr is BINARY_DOUBLE, then the function returns expr. ■ The optional 'fmt' and 'nlsparam' arguments are valid only if expr is a character string. They serve the same purpose as for the TO_CHAR (number) function. – The case-insensitive string 'INF' is converted to positive infinity. – The case-insensitive string '-INF' is converted to negative identity. – The case-insensitive string 'NaN' is converted to NaN (not a number). You cannot use a floating-point number format element (F, f, D, or d) in a character string expr. Conversions from character strings or NUMBER to BINARY_DOUBLE can be inexact, because the NUMBER and character types use decimal precision to represent the numeric value, and BINARY_DOUBLE uses binary precision. Conversions from BINARY_FLOAT to BINARY_DOUBLE are exact. Examples The examples that follow are based on a table with three columns, each with a different numeric datatype: CREATE TABLE float_point_demo (dec_num NUMBER(10,2), bin_double BINARY_DOUBLE, bin_float BINARY_FLOAT); INSERT INTO float_point_demo VALUES (1234.56,1234.56,1234.56); SELECT * FROM float_point_demo; DEC_NUM BIN_DOUBLE BIN_FLOAT ---------- ---------- ---------- 1234.56 1.235E+003 1.235E+003 The following example converts a value of datatype NUMBER to a value of datatype BINARY_DOUBLE: SELECT dec_num, TO_BINARY_DOUBLE(dec_num) FROM float_point_demo; DEC_NUM TO_BINARY_DOUBLE(DEC_NUM) ---------- ------------------------- See Also: TO_CHAR (number) on page 5-193 and "Floating-Point Numbers" on page 2-11 TO_BINARY_DOUBLE ( expr , fmt , ’ nlsparam ’ )
- 351. TO_BINARY_FLOAT Functions 5-189 1234.56 1.235E+003 The following example compares extracted dump information from the dec_num and bin_double columns: SELECT DUMP(dec_num) "Decimal", DUMP(bin_double) "Double" FROM float_point_demo; Decimal Double --------------------------- --------------------------------------------- Typ=2 Len=4: 194,13,35,57 Typ=101 Len=8: 192,147,74,61,112,163,215,10 TO_BINARY_FLOAT Syntax Purpose TO_BINARY_FLOAT returns a single-precision floating-point number. ■ expr can be a character string or a numeric value of type NUMBER, BINARY_ FLOAT, or BINARY_DOUBLE. If expr is BINARY_FLOAT, then the function returns expr. ■ The optional 'fmt' and 'nlsparam' arguments are valid only if expr is a character string. They serve the same purpose as for the TO_CHAR (number) function. – The incase-sensitive string 'INF' is converted to positive infinity. – The incase-sensitive string '-INF' is converted to negative identity. – The incase-sensitive string 'NaN' is converted to NaN (not a number). You cannot use a floating-point number format element (F, f, D, or d) in a character string expr. Conversions from character strings or NUMBER to BINARY_FLOAT can be inexact, because the NUMBER and character types use decimal precision to represent the numeric value and BINARY_FLOAT uses binary precision. Conversions from BINARY_DOUBLE to BINARY_FLOAT are inexact if the BINARY_ DOUBLE value uses more bits of precision than supported by the BINARY_FLOAT. Examples Using table float_point_demo created for TO_BINARY_DOUBLE on page 5-188, the following example converts a value of datatype NUMBER to a value of datatype BINARY_FLOAT: SELECT dec_num, TO_BINARY_FLOAT(dec_num) FROM float_point_demo; See Also: TO_CHAR (number) on page 5-193 and "Floating-Point Numbers" on page 2-11 TO_BINARY_FLOAT ( expr , fmt , ’ nlsparam ’ )
- 352. TO_CHAR (character) 5-190 Oracle Database SQL Reference DEC_NUM TO_BINARY_FLOAT(DEC_NUM) ---------- ------------------------ 1234.56 1.235E+003 TO_CHAR (character) Syntax to_char_char::= Purpose TO_CHAR (character) converts NCHAR, NVARCHAR2, CLOB, or NCLOB data to the database character set. The value returned is always VARCHAR2. When you use this function to convert a character LOB into the database character set, if the LOB value to be converted is larger than the target type, then the database returns an error. You can use this function in conjunction with any of the XML functions to generate a date in the database format rather than the XML Schema standard format. Examples The following example interprets a simple string as character data: SELECT TO_CHAR('01110') FROM DUAL; TO_CH ----- 01110 Compare this example with the first example for TO_CHAR (number) on page 5-193. The following example converts some CLOB data from the pm.print_media table to the database character set: SELECT TO_CHAR(ad_sourcetext) FROM print_media WHERE product_id = 2268; TO_CHAR(AD_SOURCETEXT) -------------------------------------------------------------------- ****************************** TIGER2 2268...Standard Hayes Compatible Modem Product ID: 2268 The #1 selling modem in the universe! Tiger2's modem includes call management and Internet voicing. Make real-time full duplex phone calls at the same time you're online. See Also: ■ Oracle XML DB Developer's Guide for information about formatting of XML dates and timestamps, including examples ■ "XML Functions" on page 5-7 for a listing of the XML function TO_CHAR ( nchar clob nclob )
- 353. TO_CHAR (datetime) Functions 5-191 ********************************** TO_CHAR (datetime) Syntax to_char_date::= Purpose TO_CHAR (datetime) converts a datetime or interval value of DATE, TIMESTAMP, TIMESTAMP WITH TIME ZONE, or TIMESTAMP WITH LOCAL TIME ZONE datatype to a value of VARCHAR2 datatype in the format specified by the date format fmt. If you omit fmt, then date is converted to a VARCHAR2 value as follows: ■ DATE values are converted to values in the default date format. ■ TIMESTAMP and TIMESTAMP WITH LOCAL TIME ZONE values are converted to values in the default timestamp format. ■ TIMESTAMP WITH TIME ZONE values are converted to values in the default timestamp with time zone format. Please refer to "Format Models" on page 2-54 for information on datetime formats. The 'nlsparam' argument specifies the language in which month and day names and abbreviations are returned. This argument can have this form: 'NLS_DATE_LANGUAGE = language' If you omit 'nlsparam', then this function uses the default date language for your session. Examples The following example uses this table: CREATE TABLE date_tab ( ts_col TIMESTAMP, tsltz_col TIMESTAMP WITH LOCAL TIME ZONE, tstz_col TIMESTAMP WITH TIME ZONE); The example shows the results of applying TO_CHAR to different TIMESTAMP datatypes. The result for a TIMESTAMP WITH LOCAL TIME ZONE column is sensitive to session time zone, whereas the results for the TIMESTAMP and TIMESTAMP WITH TIME ZONE columns are not sensitive to session time zone: ALTER SESSION SET TIME_ZONE = '-8:00'; INSERT INTO date_tab VALUES ( TIMESTAMP'1999-12-01 10:00:00', TIMESTAMP'1999-12-01 10:00:00', TIMESTAMP'1999-12-01 10:00:00'); INSERT INTO date_tab VALUES ( TIMESTAMP'1999-12-02 10:00:00 -8:00', TIMESTAMP'1999-12-02 10:00:00 -8:00', TO_CHAR ( datetime interval , fmt , ’ nlsparam ’ )
- 354. TO_CHAR (number) 5-192 Oracle Database SQL Reference TIMESTAMP'1999-12-02 10:00:00 -8:00'); SELECT TO_CHAR(ts_col, 'DD-MON-YYYY HH24:MI:SSxFF'), TO_CHAR(tstz_col, 'DD-MON-YYYY HH24:MI:SSxFF TZH:TZM') FROM date_tab; TO_CHAR(TS_COL,'DD-MON-YYYYHH2 TO_CHAR(TSTZ_COL,'DD-MON-YYYYHH24:MI: ------------------------------ ------------------------------------- 01-DEC-1999 10:00:00 01-DEC-1999 10:00:00.000000 -08:00 02-DEC-1999 10:00:00 02-DEC-1999 10:00:00.000000 -08:00 SELECT SESSIONTIMEZONE, TO_CHAR(tsltz_col, 'DD-MON-YYYY HH24:MI:SSxFF') FROM date_tab; SESSIONTIMEZONE TO_CHAR(TSLTZ_COL,'DD-MON-YYYY --------------- ------------------------------ -08:00 01-DEC-1999 10:00:00.000000 -08:00 02-DEC-1999 10:00:00.000000 ALTER SESSION SET TIME_ZONE = '-5:00'; SELECT TO_CHAR(ts_col, 'DD-MON-YYYY HH24:MI:SSxFF'), TO_CHAR(tstz_col, 'DD-MON-YYYY HH24:MI:SSxFF TZH:TZM') FROM date_tab; TO_CHAR(TS_COL,'DD-MON-YYYYHH2 TO_CHAR(TSTZ_COL,'DD-MON-YYYYHH24:MI: ------------------------------ ------------------------------------- 01-DEC-1999 10:00:00.000000 01-DEC-1999 10:00:00.000000 -08:00 02-DEC-1999 10:00:00.000000 02-DEC-1999 10:00:00.000000 -08:00 SELECT SESSIONTIMEZONE, TO_CHAR(tsltz_col, 'DD-MON-YYYY HH24:MI:SSxFF') FROM date_tab; SESSIONTIMEZONE TO_CHAR(TSLTZ_COL,'DD-MON-YYYY ------------------------- ------------------------------ -05:00 01-DEC-1999 13:00:00.000000 -05:00 02-DEC-1999 13:00:00.000000 TO_CHAR (number) Syntax to_char_number::= Purpose TO_CHAR (number) converts n to a value of VARCHAR2 datatype, using the optional number format fmt. The value n can be of type NUMBER, BINARY_FLOAT, or BINARY_ DOUBLE. If you omit fmt, then n is converted to a VARCHAR2 value exactly long enough to hold its significant digits. Please refer to "Format Models" on page 2-54 for information on number formats. TO_CHAR ( n , fmt , ’ nlsparam ’ )
- 355. TO_CHAR (number) Functions 5-193 The 'nlsparam' argument specifies these characters that are returned by number format elements: ■ Decimal character ■ Group separator ■ Local currency symbol ■ International currency symbol This argument can have this form: 'NLS_NUMERIC_CHARACTERS = ''dg'' NLS_CURRENCY = ''text'' NLS_ISO_CURRENCY = territory ' The characters d and g represent the decimal character and group separator, respectively. They must be different single-byte characters. Within the quoted string, you must use two single quotation marks around the parameter values. Ten characters are available for the currency symbol. If you omit 'nlsparam' or any one of the parameters, then this function uses the default parameter values for your session. Examples The following statement uses implicit conversion to combine a string and a number into a number: SELECT TO_CHAR('01110' + 1) FROM dual; TO_C ---- 1111 Compare this example with the first example for TO_CHAR (character) on page 5-190. In the next example, the output is blank padded to the left of the currency symbol. SELECT TO_CHAR(-10000,'L99G999D99MI') "Amount" FROM DUAL; Amount -------------- $10,000.00- SELECT TO_CHAR(-10000,'L99G999D99MI', 'NLS_NUMERIC_CHARACTERS = '',.'' NLS_CURRENCY = ''AusDollars'' ') "Amount" FROM DUAL; Amount ------------------- AusDollars10.000,00- In the optional number format fmt, L designates local currency symbol and MI designates a trailing minus sign. See Table 2–17, " Matching Character Data and Format Models with the FX Format Model Modifier" on page 2-66 for a complete listing of number format elements.
- 356. TO_CLOB 5-194 Oracle Database SQL Reference TO_CLOB Syntax Purpose TO_CLOB converts NCLOB values in a LOB column or other character strings to CLOB values. char can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. Oracle Database executes this function by converting the underlying LOB data from the national character set to the database character set. Examples The following statement converts NCLOB data from the sample pm.print_media table to CLOB and inserts it into a CLOB column, replacing existing data in that column. UPDATE PRINT_MEDIA SET AD_FINALTEXT = TO_CLOB (AD_FLTEXTN); TO_DATE Syntax Purpose TO_DATE converts char of CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype to a value of DATE datatype. The fmt is a datetime model format specifying the format of char. If you omit fmt, then char must be in the default date format. If fmt is J, for Julian, then char must be an integer. The default date format is determined implicitly by the NLS_TERRITORY initialization parameter or can be set explicitly by the NLS_DATE_FORMAT parameter. The 'nlsparam' argument has the same purpose in this function as in the TO_CHAR function for date conversion. Do not use the TO_DATE function with a DATE value for the char argument. The first two digits of the returned DATE value can differ from the original char, depending on fmt or the default date format. This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion. Note: This function does not convert data to any of the other datetime datatypes. For information on other datetime conversions, please refer to TO_TIMESTAMP on page 5-201, TO_TIMESTAMP_TZ on page 5-202, TO_DSINTERVAL on page 5-196, and TO_ YMINTERVAL on page 5-203. TO_CLOB ( lob_column char ) TO_DATE ( char , fmt , ’ nlsparam ’ )
- 357. TO_DSINTERVAL Functions 5-195 Examples The following example converts a character string into a date: SELECT TO_DATE( 'January 15, 1989, 11:00 A.M.', 'Month dd, YYYY, HH:MI A.M.', 'NLS_DATE_LANGUAGE = American') FROM DUAL; TO_DATE(' --------- 15-JAN-89 The value returned reflects the default date format if the NLS_TERRITORY parameter is set to 'AMERICA'. Different NLS_TERRITORY values result in different default date formats: ALTER SESSION SET NLS_TERRITORY = 'KOREAN'; SELECT TO_DATE( 'January 15, 1989, 11:00 A.M.', 'Month dd, YYYY, HH:MI A.M.', 'NLS_DATE_LANGUAGE = American') FROM DUAL; TO_DATE( -------- 89/01/15 TO_DSINTERVAL Syntax Purpose TO_DSINTERVAL converts a character string of CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype to an INTERVAL DAY TO SECOND value. ■ char is the character string to be converted. ■ The only valid nlsparam you can specify in this function is NLS_NUMERIC_ CHARACTERS. This argument can have the form: NLS_NUMERIC_CHARACTERS = "dg" where d and g represent the decimal character and group separator respectively. Neither character can be a space. Examples The following example selects from the employees table the employees who had worked for the company for at least 100 days on January 1, 1990: See Also: "Datetime Format Models" on page 2-58 and "Datatype Comparison Rules" on page 2-37 for more information TO_DSINTERVAL ( char , ’ nlsparam ’ )
- 358. TO_LOB 5-196 Oracle Database SQL Reference SELECT employee_id, last_name FROM employees WHERE hire_date + TO_DSINTERVAL('100 10:00:00') <= DATE '1990-01-01'; EMPLOYEE_ID LAST_NAME ----------- --------------- 100 King 101 Kochhar 200 Whalen TO_LOB Syntax Purpose TO_LOB converts LONG or LONG RAW values in the column long_column to LOB values. You can apply this function only to a LONG or LONG RAW column, and only in the select list of a subquery in an INSERT statement. Before using this function, you must create a LOB column to receive the converted LONG values. To convert LONG values, create a CLOB column. To convert LONG RAW values, create a BLOB column. You cannot use the TO_LOB function to convert a LONG column to a LOB column in the subquery of a CREATE TABLE ... AS SELECT statement if you are creating an index-organized table. Instead, create the index-organized table without the LONG column, and then use the TO_LOB function in an INSERT ... AS SELECT statement. Example The following syntax shows how to use the TO_LOB function on your LONG data in a hypothetical table old_table: CREATE TABLE new_table (col1, col2, ... lob_col CLOB); INSERT INTO new_table (select o.col1, o.col2, ... TO_LOB(o.old_long_col) FROM old_table o; TO_MULTI_BYTE Syntax See Also: ■ the modify_col_properties clause of ALTER TABLE on page 12-2 for an alternative method of converting LONG columns to LOB ■ INSERT on page 18-51 for information on the subquery of an INSERT statement TO_LOB ( long_column ) TO_MULTI_BYTE ( char )
- 359. TO_NCHAR (character) Functions 5-197 Purpose TO_MULTI_BYTE returns char with all of its single-byte characters converted to their corresponding multibyte characters. char can be of datatype CHAR, VARCHAR2, NCHAR, or NVARCHAR2. The value returned is in the same datatype as char. Any single-byte characters in char that have no multibyte equivalents appear in the output string as single-byte characters. This function is useful only if your database character set contains both single-byte and multibyte characters. This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion. Examples The following example illustrates converting from a single byte A to a multibyte A in UTF8: SELECT dump(TO_MULTI_BYTE( 'A')) FROM DUAL; DUMP(TO_MULTI_BYTE('A')) ------------------------ Typ=1 Len=3: 239,188,161 TO_NCHAR (character) Syntax to_nchar_char::= Purpose TO_NCHAR (character) converts a character string, CHAR, VARCHAR2, CLOB, or NCLOB value to the national character set. The value returned is always NVARCHAR2. This function is equivalent to the TRANSLATE ... USING function with a USING clause in the national character set. Examples The following example converts VARCHAR2 data from the oe.customers table to the national character set: SELECT TO_NCHAR(cust_last_name) FROM customers WHERE customer_id=103; TO_NCHAR(CUST_LAST_NAME) -------------------------------------------------- Taylor See Also: "Datatype Comparison Rules" on page 2-37 for more information. See Also: "Data Conversion" on page 2-40 and TRANSLATE ... USING on page 5-204 TO_NCHAR ( char clob nclob )
- 360. TO_NCHAR (datetime) 5-198 Oracle Database SQL Reference TO_NCHAR (datetime) Syntax to_nchar_date::= Purpose TO_NCHAR (datetime) converts a datetime or interval value of DATE, TIMESTAMP, TIMESTAMP WITH TIME ZONE, TIMESTAMP WITH LOCAL TIME ZONE, INTERVAL MONTH TO YEAR, or INTERVAL DAY TO SECOND datatype from the database character set to the national character set. Examples The following example converts the order_date of all orders whose status is 9 to the national character set: SELECT TO_NCHAR(order_date) FROM orders WHERE order_status > 9; TO_NCHAR(ORDER_DATE) ---------------------------- 14-SEP-99 08.53.40.223345 AM 13-SEP-99 09.19.00.654279 AM 27-JUN-00 08.53.32.335522 PM 26-JUN-00 09.19.43.190089 PM 06-DEC-99 01.22.34.225609 PM TO_NCHAR (number) Syntax to_nchar_number::= Purpose TO_NCHAR (number) converts n to a string in the national character set. The value n can be of type NUMBER, BINARY_FLOAT, or BINARY_DOUBLE. The function returns a value of the same type as the argument. The optional fmt and 'nlsparam' corresponding to n can be of DATE, TIMESTAMP, TIMESTAMP WITH TIME ZONE, TIMESTAMP WITH LOCAL TIME ZONE, INTERVAL MONTH TO YEAR, or INTERVAL DAY TO SECOND datatype. Examples The following example converts the customer_id values from the sample table oe.orders to the national character set: TO_NCHAR ( datetime interval , fmt , ’ nlsparam ’ ) TO_NCHAR ( n , fmt , ’ nlsparam ’ )
- 361. TO_NUMBER Functions 5-199 SELECT TO_NCHAR(customer_id) "NCHAR_Customer_ID" FROM orders WHERE order_status > 9; NCHAR_Customer_ID ----------------- 102 103 148 149 148 TO_NCLOB Syntax Purpose TO_NCLOB converts CLOB values in a LOB column or other character strings to NCLOB values. char can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. Oracle Database implements this function by converting the character set of char from the database character set to the national character set. Examples The following example inserts some character data into an NCLOB column of the pm.print_media table by first converting the data with the TO_NCLOB function: INSERT INTO print_media (product_id, ad_id, ad_fltextn) VALUES (3502, 31001, TO_NCLOB('Placeholder for new product description')); TO_NUMBER Syntax Purpose TO_NUMBER converts expr to a value of NUMBER datatype. The expr can be a BINARY_FLOAT or BINARY_DOUBLE value or a value of CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype containing a number in the format specified by the optional format model fmt. This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion. See Also: "Datatype Comparison Rules" on page 2-37 for more information. TO_NCLOB ( lob_column char ) TO_NUMBER ( expr , fmt , ’ nlsparam ’ )
- 362. TO_SINGLE_BYTE 5-200 Oracle Database SQL Reference Examples The following examples convert character string data into a number: UPDATE employees SET salary = salary + TO_NUMBER('100.00', '9G999D99') WHERE last_name = 'Perkins'; The 'nlsparam' argument in this function has the same purpose as it does in the TO_CHAR function for number conversions. Please refer to TO_CHAR (number) on page 5-193 for more information. SELECT TO_NUMBER('-AusDollars100','L9G999D99', ' NLS_NUMERIC_CHARACTERS = '',.'' NLS_CURRENCY = ''AusDollars'' ') "Amount" FROM DUAL; Amount ---------- -100 TO_SINGLE_BYTE Syntax Purpose TO_SINGLE_BYTE returns char with all of its multibyte characters converted to their corresponding single-byte characters. char can be of datatype CHAR, VARCHAR2, NCHAR, or NVARCHAR2. The value returned is in the same datatype as char. Any multibyte characters in char that have no single-byte equivalents appear in the output as multibyte characters. This function is useful only if your database character set contains both single-byte and multibyte characters. This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion. Examples The following example illustrates going from a multibyte A in UTF8 to a single byte ASCII A: SELECT TO_SINGLE_BYTE( CHR(15711393)) FROM DUAL; T - A See Also: "Datatype Comparison Rules" on page 2-37 for more information. TO_SINGLE_BYTE ( char )
- 363. TO_TIMESTAMP_TZ Functions 5-201 TO_TIMESTAMP Syntax Purpose TO_TIMESTAMP converts char of CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype to a value of TIMESTAMP datatype. The optional fmt specifies the format of char. If you omit fmt, then char must be in the default format of the TIMESTAMP datatype, which is determined by the NLS_ TIMESTAMP_FORMAT initialization parameter. The optional 'nlsparam' argument has the same purpose in this function as in the TO_CHAR function for date conversion. This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion. Examples The following example converts a character string to a timestamp. The character string is not in the default TIMESTAMP format, so the format mask must be specified: SELECT TO_TIMESTAMP ('10-Sep-02 14:10:10.123000', 'DD-Mon-RR HH24:MI:SS.FF') FROM DUAL; TO_TIMESTAMP('10-SEP-0214:10:10.123000','DD-MON-RRHH24:MI:SS.FF') --------------------------------------------------------------------------- 10-SEP-02 02.10.10.123000000 PM TO_TIMESTAMP_TZ Syntax Purpose TO_TIMESTAMP_TZ converts char of CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype to a value of TIMESTAMP WITH TIME ZONE datatype. See Also: "Datatype Comparison Rules" on page 2-37 for more information. See Also: NLS_TIMESTAMP_FORMAT parameter for information on the default TIMESTAMP format and "Datetime Format Models" on page 2-58 for information on specifying the format mask Note: This function does not convert character strings to TIMESTAMP WITH LOCAL TIME ZONE. To do this, use a CAST function, as shown in CAST on page 5-24. TO_TIMESTAMP ( char , fmt , ’ nlsparam ’ ) TO_TIMESTAMP_TZ ( char , fmt , ’ nlsparam ’ )
- 364. TO_YMINTERVAL 5-202 Oracle Database SQL Reference The optional fmt specifies the format of char. If you omit fmt, then char must be in the default format of the TIMESTAMP WITH TIME ZONE datatype. The optional 'nlsparam' has the same purpose in this function as in the TO_CHAR function for date conversion. Examples The following example converts a character string to a value of TIMESTAMP WITH TIME ZONE: SELECT TO_TIMESTAMP_TZ('1999-12-01 11:00:00 -8:00', 'YYYY-MM-DD HH:MI:SS TZH:TZM') FROM DUAL; TO_TIMESTAMP_TZ('1999-12-0111:00:00-08:00','YYYY-MM-DDHH:MI:SSTZH:TZM') -------------------------------------------------------------------- 01-DEC-99 11.00.00.000000000 AM -08:00 The following example casts a null column in a UNION operation as TIMESTAMP WITH LOCAL TIME ZONE using the sample tables oe.order_items and oe.orders: SELECT order_id, line_item_id, CAST(NULL AS TIMESTAMP WITH LOCAL TIME ZONE) order_date FROM order_items UNION SELECT order_id, to_number(null), order_date FROM orders; ORDER_ID LINE_ITEM_ID ORDER_DATE ---------- ------------ ----------------------------------- 2354 1 2354 2 2354 3 2354 4 2354 5 2354 6 2354 7 2354 8 2354 9 2354 10 2354 11 2354 12 2354 13 2354 14-JUL-00 05.18.23.234567 PM 2355 1 2355 2 ... TO_YMINTERVAL Syntax Purpose TO_YMINTERVAL converts a character string of CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype to an INTERVAL YEAR TO MONTH type, where char is the character string to be converted. TO_YMINTERVAL ( char )
- 365. TRANSLATE Functions 5-203 Examples The following example calculates for each employee in the sample hr.employees table a date one year two months after the hire date: SELECT hire_date, hire_date + TO_YMINTERVAL('01-02') "14 months" FROM employees; HIRE_DATE 14 months --------- --------- 17-JUN-87 17-AUG-88 21-SEP-89 21-NOV-90 13-JAN-93 13-MAR-94 03-JAN-90 03-MAR-91 21-MAY-91 21-JUL-92 . . . TRANSLATE Syntax Purpose TRANSLATE returns expr with all occurrences of each character in from_string replaced by its corresponding character in to_string. Characters in expr that are not in from_string are not replaced. If expr is a character string, then you must enclose it in single quotation marks. The argument from_string can contain more characters than to_string. In this case, the extra characters at the end of from_ string have no corresponding characters in to_string. If these extra characters appear in char, then they are removed from the return value. You cannot use an empty string for to_string to remove all characters in from_ string from the return value. Oracle Database interprets the empty string as null, and if this function has a null argument, then it returns null. TRANSLATE provides functionality related to that provided by the REPLACE function. REPLACE lets you substitute a single string for another single string, as well as remove character strings. TRANSLATE lets you make several single-character, one-to-one substitutions in one operation. This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion. Examples The following statement translates a book title into a string that could be used (for example) as a filename. The from_string contains four characters: a space, asterisk, slash, and apostrophe (with an extra apostrophe as the escape character). The to_ string contains only three underscores. This leaves the fourth character in the from_ string without a corresponding replacement, so apostrophes are dropped from the returned value. SELECT TRANSLATE('SQL*Plus User''s Guide', ' */''', '___') FROM DUAL; TRANSLATE('SQL*PLUSU See Also: "Datatype Comparison Rules" on page 2-37 for more information and REPLACE on page 5-148 TRANSLATE ( expr , from_string , to_string )
- 366. TRANSLATE ... USING 5-204 Oracle Database SQL Reference -------------------- SQL_Plus_Users_Guide TRANSLATE ... USING Syntax Purpose TRANSLATE ... USING converts char into the character set specified for conversions between the database character set and the national character set. The char argument is the expression to be converted. ■ Specifying the USING CHAR_CS argument converts char into the database character set. The output datatype is VARCHAR2. ■ Specifying the USING NCHAR_CS argument converts char into the national character set. The output datatype is NVARCHAR2. This function is similar to the Oracle CONVERT function, but must be used instead of CONVERT if either the input or the output datatype is being used as NCHAR or NVARCHAR2. If the input contains UCS2 code points or backslash characters (), then use the UNISTR function. Examples The following statements use data from the sample table oe.product_ descriptions to show the use of the TRANSLATE ... USING function: CREATE TABLE translate_tab (char_col VARCHAR2(100), nchar_col NVARCHAR2(50)); INSERT INTO translate_tab SELECT NULL, translated_name FROM product_descriptions WHERE product_id = 3501; SELECT * FROM translate_tab; CHAR_COL NCHAR_COL ------------------------- ------------------------- . . . C per a SPNIX4.0 - Sys C pro SPNIX4.0 - Sys C for SPNIX4.0 - Sys Note: The TRANSLATE ... USING function is supported primarily for ANSI compatibility. Oracle recommends that you use the TO_CHAR and TO_NCHAR functions, as appropriate, for converting data to the database or national character set. TO_CHAR and TO_NCHAR can take as arguments a greater variety of datatypes than TRANSLATE ... USING, which accepts only character data. See Also: CONVERT on page 5-37 and UNISTR on page 5-210 TRANSLATE ( char USING CHAR_CS NCHAR_CS )
- 367. TREAT Functions 5-205 C til SPNIX4.0 - Sys . . . UPDATE translate_tab SET char_col = TRANSLATE (nchar_col USING CHAR_CS); SELECT * FROM translate_tab; CHAR_COL NCHAR_COL ------------------------- ------------------------- . . . C per a SPNIX4.0 - Sys C per a SPNIX4.0 - Sys C pro SPNIX4.0 - Sys C pro SPNIX4.0 - Sys C for SPNIX4.0 - Sys C for SPNIX4.0 - Sys C til SPNIX4.0 - Sys C til SPNIX4.0 - Sys . . . TREAT Syntax Purpose TREAT changes the declared type of an expression. You must have the EXECUTE object privilege on type to use this function. ■ type must be some supertype or subtype of the declared type of expr. If the most specific type of expr is type (or some subtype of type), then TREAT returns expr. If the most specific type of expr is not type (or some subtype of type), then TREAT returns NULL. ■ You can specify REF only if the declared type of expr is a REF type. ■ If the declared type of expr is a REF to a source type of expr, then type must be some subtype or supertype of the source type of expr. If the most specific type of DEREF(expr) is type (or a subtype of type), then TREAT returns expr. If the most specific type of DEREF(expr) is not type (or a subtype of type), then TREAT returns NULL. This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion. Examples The following statement uses the table oe.persons, which is created in "Substitutable Table and Column Examples" on page 16-51. That table is based on the person_t type, which is created in "Type Hierarchy Example" on page 17-17. The example retrieves the salary attribute of all people in the persons table, the value being null for instances of people that are not employees. SELECT name, TREAT(VALUE(p) AS employee_t).salary salary FROM persons p; See Also: "Datatype Comparison Rules" on page 2-37 for more information TREAT ( expr AS REF schema . type )
- 368. TRIM 5-206 Oracle Database SQL Reference NAME SALARY ------------------------- ---------- Bob Joe 100000 Tim 1000 You can use the TREAT function to create an index on the subtype attributes of a substitutable column. For an example, see "Indexing on Substitutable Columns: Examples" on page 14-79. TRIM Syntax Purpose TRIM enables you to trim leading or trailing characters (or both) from a character string. If trim_character or trim_source is a character literal, then you must enclose it in single quotes. ■ If you specify LEADING, then Oracle Database removes any leading characters equal to trim_character. ■ If you specify TRAILING, then Oracle removes any trailing characters equal to trim_character. ■ If you specify BOTH or none of the three, then Oracle removes leading and trailing characters equal to trim_character. ■ If you do not specify trim_character, then the default value is a blank space. ■ If you specify only trim_source, then Oracle removes leading and trailing blank spaces. ■ The function returns a value with datatype VARCHAR2. The maximum length of the value is the length of trim_source. ■ If either trim_source or trim_character is null, then the TRIM function returns null. Both trim_character and trim_source can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The string returned is of VARCHAR2 datatype if trim_source is a character datatype and a LOB if trim_source is a LOB datatype. The return string is in the same character set as trim_source. Examples This example trims leading zeroes from the hire date of the employees in the hr schema: SELECT employee_id, TO_CHAR(TRIM(LEADING 0 FROM hire_date)) FROM employees TRIM ( LEADING TRAILING BOTH trim_character trim_character FROM trim_source )
- 369. TRUNC (number) Functions 5-207 WHERE department_id = 60; EMPLOYEE_ID TO_CHAR(T ----------- --------- 103 3-JAN-90 104 21-MAY-91 105 25-JUN-97 106 5-FEB-98 107 7-FEB-99 TRUNC (number) Syntax trunc_number::= Purpose The TRUNC (number) function returns n1 truncated to n2 decimal places. If n2 is omitted, then n1 is truncated to 0 places. n2 can be negative to truncate (make zero) n2 digits left of the decimal point. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. If you omit n2, then the function returns the same datatype as the numeric datatype of the argument. If you include n2, then the function returns NUMBER. Examples The following examples truncate numbers: SELECT TRUNC(15.79,1) "Truncate" FROM DUAL; Truncate ---------- 15.7 SELECT TRUNC(15.79,-1) "Truncate" FROM DUAL; Truncate ---------- 10 See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion TRUNC ( n1 , n2 )
- 370. TRUNC (date) 5-208 Oracle Database SQL Reference TRUNC (date) Syntax trunc_date::= Purpose The TRUNC (date) function returns date with the time portion of the day truncated to the unit specified by the format model fmt. The value returned is always of datatype DATE, even if you specify a different datetime datatype for date. If you omit fmt, then date is truncated to the nearest day. Please refer to "ROUND and TRUNC Date Functions" on page 5-235 for the permitted format models to use in fmt. Examples The following example truncates a date: SELECT TRUNC(TO_DATE('27-OCT-92','DD-MON-YY'), 'YEAR') "New Year" FROM DUAL; New Year --------- 01-JAN-92 TZ_OFFSET Syntax Purpose TZ_OFFSET returns the time zone offset corresponding to the argument based on the date the statement is executed. You can enter a valid time zone name, a time zone offset from UTC (which simply returns itself), or the keyword SESSIONTIMEZONE or DBTIMEZONE. For a listing of valid values for time_zone_name, query the TZNAME column of the V$TIMEZONE_NAMES dynamic performance view. TRUNC ( date , fmt ) TZ_OFFSET ( ’ time_zone_name ’ ’ + – hh : mi ’ SESSIONTIMEZONE DBTMEZONE )
- 371. UNISTR Functions 5-209 Examples The following example returns the time zone offset of the US/Eastern time zone from UTC: SELECT TZ_OFFSET('US/Eastern') FROM DUAL; TZ_OFFS ------- -04:00 UID Syntax Purpose UID returns an integer that uniquely identifies the session user (the user who logged on). Examples The following example returns the UID of the current user: SELECT UID FROM DUAL; UNISTR Syntax Purpose UNISTR takes as its argument a text literal or an expression that resolves to character data and returns it in the national character set. The national character set of the database can be either AL16UTF16 or UTF8. UNISTR provides support for Unicode string literals by letting you specify the Unicode encoding value of characters in the string. This is useful, for example, for inserting data into NCHAR columns. The Unicode encoding value has the form 'xxxx' where 'xxxx' is the hexadecimal value of a character in UCS-2 encoding format. Supplementary characters are encoded as two code units, the first from the high-surrogates range (U+D800 to U+DBFF), and the second from the low-surrogates range (U+DC00 to U+DFFF). To include the backslash in the string itself, precede it with another backslash (). Note: Timezone region names are needed by the daylight savings feature. The region names are stored in two time zone files. The default time zone file is a small file containing only the most common time zones to maximize performance. If your time zone is not in the default file, then you will not have daylight savings support until you provide a path to the complete (larger) file by way of the ORA_TZFILE environment variable. UID UNISTR ( string )
- 372. UPDATEXML 5-210 Oracle Database SQL Reference For portability and data preservation, Oracle recommends that in the UNISTR string argument you specify only ASCII characters and the Unicode encoding values. Examples The following example passes both ASCII characters and Unicode encoding values to the UNISTR function, which returns the string in the national character set: SELECT UNISTR('abc00e500f100f6') FROM DUAL; UNISTR ------ abcåñö UPDATEXML Syntax Purpose UPDATEXML takes as arguments an XMLType instance and an XPath-value pair and returns an XMLType instance with the updated value. If XPath_string is an XML element, then the corresponding value_expr must be an XMLType instance. If XPath_string is an attribute or text node, then the value_expr can be any scalar datatype. You can specify an absolute XPath_string with an initial slash or a relative XPath_string by omitting the initial slash. If you omit the initial slash, the context of the relative path defaults to the root node. The datatypes of the target of each XPath_string and its corresponding value_expr must match. The optional namespace_string must resolve to a VARCHAR2 value that specifies a default mapping or namespace mapping for prefixes, which Oracle Database uses when evaluating the XPath expression(s). If you update an XML element to null, Oracle removes the attributes and children of the element, and the element becomes empty. If you update the text node of an element to null, Oracle removes the text value of the element, and the element itself remains but is empty. In most cases, this function materializes an XML document in memory and updates the value. However, UPDATEXML is optimized for UPDATE statements on object-relational columns so that the function updates the value directly in the column. This optimization requires the following conditions: ■ The XMLType_instance must be the same as the column in the UPDATE ... SET clause. ■ The XPath_string must resolve to scalar content. Examples The following example updates to 4 the number of docks in the San Francisco warehouse in the sample schema OE, which has a warehouse_spec column of type XMLType: See Also: Oracle Database Globalization Support Guide for information on Unicode and national character sets UPDATEXML ( XMLType_instance , XPath_string , value_expr , , namespace_string )
- 373. USER Functions 5-211 SELECT warehouse_name, EXTRACT(warehouse_spec, '/Warehouse/Docks') "Number of Docks" FROM warehouses WHERE warehouse_name = 'San Francisco'; WAREHOUSE_NAME Number of Docks -------------------- -------------------- San Francisco <Docks>1</Docks> UPDATE warehouses SET warehouse_spec = UPDATEXML(warehouse_spec, '/Warehouse/Docks/text()',4) WHERE warehouse_name = 'San Francisco'; 1 row updated. SELECT warehouse_name, EXTRACT(warehouse_spec, '/Warehouse/Docks') "Number of Docks" FROM warehouses WHERE warehouse_name = 'San Francisco'; WAREHOUSE_NAME Number of Docks -------------------- -------------------- San Francisco <Docks>4</Docks> UPPER Syntax Purpose UPPER returns char, with all letters uppercase. char can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The return value is the same datatype as char. The database sets the case of the characters based on the binary mapping defined for the underlying character set. For linguistic-sensitive uppercase, please refer to NLS_UPPER on page 5-106. Examples The following example returns each employee’s last name in uppercase: SELECT UPPER(last_name) "Uppercase" FROM employees; USER Syntax UPPER ( char ) USER
- 374. USERENV 5-212 Oracle Database SQL Reference Purpose USER returns the name of the session user (the user who logged on) with the datatype VARCHAR2. Oracle Database compares values of this function with blank-padded comparison semantics. In a distributed SQL statement, the UID and USER functions together identify the user on your local database. You cannot use these functions in the condition of a CHECK constraint. Examples The following example returns the current user and the user's UID: SELECT USER, UID FROM DUAL; USERENV Syntax Purpose USERENV returns information about the current session. This information can be useful for writing an application-specific audit trail table or for determining the language-specific characters currently used by your session. You cannot use USERENV in the condition of a CHECK constraint. Table 5–13 describes the values for the parameter argument. All calls to USERENV return VARCHAR2 data except for calls with the SESSIONID and ENTRYID parameters, which return NUMBER. Note: USERENV is a legacy function that is retained for backward compatibility. Oracle recommends that you use the SYS_CONTEXT function with the built-in USERENV namespace for current functionality. See SYS_CONTEXT on page 5-176 for more information. Table 5–13 Parameters of the USERENV Function Parameter Return Value CLIENT_INFO CLIENT_INFO returns up to 64 bytes of user session information that can be stored by an application using the DBMS_APPLICATION_INFO package. Caution: Some commercial applications may be using this context value. Please refer to the applicable documentation for those applications to determine what restrictions they may impose on use of this context area. See Also: ■ Oracle Database Concepts for more information on application context ■ CREATE CONTEXT on page 14-9 and SYS_CONTEXT on page 5-176 USERENV ( ’ parameter ’ )
- 375. VALUE Functions 5-213 Examples The following example returns the LANGUAGE parameter of the current session: SELECT USERENV('LANGUAGE') "Language" FROM DUAL; Language ----------------------------------- AMERICAN_AMERICA.WE8ISO8859P1 VALUE Syntax Purpose VALUE takes as its argument a correlation variable (table alias) associated with a row of an object table and returns object instances stored in the object table. The type of the object instances is the same type as the object table. Examples The following example uses the sample table oe.persons, which is created in "Substitutable Table and Column Examples" on page 16-51: SELECT VALUE(p) FROM persons p; VALUE(P)(NAME, SSN) ------------------------------------------------------------- PERSON_T('Bob', 1234) EMPLOYEE_T('Joe', 32456, 12, 100000) PART_TIME_EMP_T('Tim', 5678, 13, 1000, 20) ENTRYID The current audit entry number. The audit entryid sequence is shared between fine-grained audit records and regular audit records. You cannot use this attribute in distributed SQL statements. ISDBA ISDBA returns 'TRUE' if the user has been authenticated as having DBA privileges either through the operating system or through a password file. LANG LANG returns the ISO abbreviation for the language name, a shorter form than the existing 'LANGUAGE' parameter. LANGUAGE LANGUAGE returns the language and territory used by the current session along with the database character set in this form: language_territory.characterset SESSIONID SESSIONID returns the auditing session identifier. You cannot specify this parameter in distributed SQL statements. TERMINAL TERMINAL returns the operating system identifier for the terminal of the current session. In distributed SQL statements, this parameter returns the identifier for your local session. In a distributed environment, this parameter is supported only for remote SELECT statements, not for remote INSERT, UPDATE, or DELETE operations. Table 5–13 (Cont.) Parameters of the USERENV Function Parameter Return Value VALUE ( correlation_variable )
- 376. VAR_POP 5-214 Oracle Database SQL Reference VAR_POP Syntax Purpose VAR_POP returns the population variance of a set of numbers after discarding the nulls in this set. You can use it as both an aggregate and analytic function. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument. If the function is applied to an empty set, then it returns null. The function makes the following calculation: (SUM(expr2 ) - SUM(expr)2 / COUNT(expr)) / COUNT(expr) Aggregate Example The following example returns the population variance of the salaries in the employees table: SELECT VAR_POP(salary) FROM employees; VAR_POP(SALARY) --------------- 15140307.5 Analytic Example The following example calculates the cumulative population and sample variances in the sh.sales table of the monthly sales in 1998: SELECT t.calendar_month_desc, VAR_POP(SUM(s.amount_sold)) OVER (ORDER BY t.calendar_month_desc) "Var_Pop", VAR_SAMP(SUM(s.amount_sold)) OVER (ORDER BY t.calendar_month_desc) "Var_Samp" FROM sales s, times t WHERE s.time_id = t.time_id AND t.calendar_year = 1998 GROUP BY t.calendar_month_desc; See Also: "IS OF type Condition" on page 7-23 for information on using IS OF type conditions with the VALUE function See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion See Also: "About SQL Expressions" on page 6-1 for information on valid forms of expr and "Aggregate Functions" on page 5-8 VAR_POP ( expr ) OVER ( analytic_clause )
- 377. VAR_SAMP Functions 5-215 CALENDAR Var_Pop Var_Samp -------- ---------- ---------- 1998-01 0 1998-02 6.1321E+11 1.2264E+12 1998-03 4.7058E+11 7.0587E+11 1998-04 4.6929E+11 6.2572E+11 1998-05 1.5524E+12 1.9405E+12 1998-06 2.3711E+12 2.8453E+12 1998-07 3.7464E+12 4.3708E+12 1998-08 3.7852E+12 4.3260E+12 1998-09 3.5753E+12 4.0222E+12 1998-10 3.4343E+12 3.8159E+12 1998-11 3.4245E+12 3.7669E+12 1998-12 4.8937E+12 5.3386E+12 VAR_SAMP Syntax Purpose VAR_SAMP returns the sample variance of a set of numbers after discarding the nulls in this set. You can use it as both an aggregate and analytic function. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument. If the function is applied to an empty set, then it returns null. The function makes the following calculation: (SUM(expr2 ) - SUM(expr)2 / COUNT(expr)) / (COUNT(expr) - 1) This function is similar to VARIANCE, except that given an input set of one element, VARIANCE returns 0 and VAR_SAMP returns null. Aggregate Example The following example returns the sample variance of the salaries in the sample employees table. SELECT VAR_SAMP(salary) FROM employees; VAR_SAMP(SALARY) ---------------- 15283140.5 See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion See Also: "About SQL Expressions" on page 6-1 for information on valid forms of expr and "Aggregate Functions" on page 5-8 VAR_SAMP ( expr ) OVER ( analytic_clause )
- 378. VARIANCE 5-216 Oracle Database SQL Reference Analytic Example Please refer to the analytic example for VAR_POP on page 5-214. VARIANCE Syntax Purpose VARIANCE returns the variance of expr. You can use it as an aggregate or analytic function. Oracle Database calculates the variance of expr as follows: ■ 0 if the number of rows in expr = 1 ■ VAR_SAMP if the number of rows in expr > 1 If you specify DISTINCT, then you can specify only the query_partition_clause of the analytic_clause. The order_by_clause and windowing_clause are not allowed. This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument. Aggregate Example The following example calculates the variance of all salaries in the sample employees table: SELECT VARIANCE(salary) "Variance" FROM employees; Variance ---------- 15283140.5 Analytic Example The following example returns the cumulative variance of salary values in Department 30 ordered by hire date. SELECT last_name, salary, VARIANCE(salary) OVER (ORDER BY hire_date) "Variance" FROM employees WHERE department_id = 30; See Also: "Analytic Functions" on page 5-9 for information on syntax, semantics, and restrictions See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion, "About SQL Expressions" on page 6-1 for information on valid forms of expr and "Aggregate Functions" on page 5-8 VARIANCE ( DISTINCT ALL expr ) OVER ( analytic_clause )
- 379. WIDTH_BUCKET Functions 5-217 LAST_NAME SALARY Variance --------------- ---------- ---------- Raphaely 11000 0 Khoo 3100 31205000 Tobias 2800 21623333.3 Baida 2900 16283333.3 Himuro 2600 13317000 Colmenares 2500 11307000 VSIZE Syntax Purpose VSIZE returns the number of bytes in the internal representation of expr. If expr is null, then this function returns null. This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion. Examples The following example returns the number of bytes in the last_name column of the employees in department 10: SELECT last_name, VSIZE (last_name) "BYTES" FROM employees WHERE department_id = 10; LAST_NAME BYTES --------------- ---------- Whalen 6 WIDTH_BUCKET Syntax Purpose WIDTH_BUCKET lets you construct equiwidth histograms, in which the histogram range is divided into intervals that have identical size. (Compare this function with NTILE, which creates equiheight histograms.) Ideally each bucket is a closed-open interval of the real number line. For example, a bucket can be assigned to scores between 10.00 and 19.999... to indicate that 10 is included in the interval and 20 is excluded. This is sometimes denoted [10, 20). For a given expression, WIDTH_BUCKET returns the bucket number into which the value of this expression would fall after being evaluated. See Also: "Datatype Comparison Rules" on page 2-37 for more information VSIZE ( expr ) WIDTH_BUCKET ( expr , min_value , max_value , num_buckets )
- 380. WIDTH_BUCKET 5-218 Oracle Database SQL Reference ■ expr is the expression for which the histogram is being created. This expression must evaluate to a numeric or datetime value or to a value that can be implicitly converted to a numeric or datetime value. If expr evaluates to null, then the expression returns null. ■ min_value and max_value are expressions that resolve to the end points of the acceptable range for expr. Both of these expressions must also evaluate to numeric or datetime values, and neither can evaluate to null. ■ num_buckets is an expression that resolves to a constant indicating the number of buckets. This expression must evaluate to a positive integer. When needed, Oracle Database creates an underflow bucket numbered 0 and an overflow bucket numbered num_buckets+1. These buckets handle values less than min_value and more than max_value and are helpful in checking the reasonableness of endpoints. Examples The following example creates a ten-bucket histogram on the credit_limit column for customers in Switzerland in the sample table oe.customers and returns the bucket number ("Credit Group") for each customer. Customers with credit limits greater than the maximum value are assigned to the overflow bucket, 11: SELECT customer_id, cust_last_name, credit_limit, WIDTH_BUCKET(credit_limit, 100, 5000, 10) "Credit Group" FROM customers WHERE nls_territory = 'SWITZERLAND' ORDER BY "Credit Group"; CUSTOMER_ID CUST_LAST_NAME CREDIT_LIMIT Credit Group ----------- -------------------- ------------ ------------ 825 Dreyfuss 500 1 826 Barkin 500 1 853 Palin 400 1 827 Siegel 500 1 843 Oates 700 2 844 Julius 700 2 835 Eastwood 1200 3 840 Elliott 1400 3 842 Stern 1400 3 841 Boyer 1400 3 837 Stanton 1200 3 836 Berenger 1200 3 848 Olmos 1800 4 849 Kaurusmdki 1800 4 828 Minnelli 2300 5 829 Hunter 2300 5 852 Tanner 2300 5 851 Brown 2300 5 850 Finney 2300 5 830 Dutt 3500 7 831 Bel Geddes 3500 7 832 Spacek 3500 7 838 Nicholson 3500 7 839 Johnson 3500 7 833 Moranis 3500 7 834 Idle 3500 7 See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion
- 381. XMLAGG Functions 5-219 845 Fawcett 5000 11 846 Brando 5000 11 847 Streep 5000 11 XMLAGG Syntax Purpose XMLAgg is an aggregate function. It takes a collection of XML fragments and returns an aggregated XML document. Any arguments that return null are dropped from the result. XMLAgg is similar to SYS_XMLAgg except that XMLAgg returns a collection of nodes but it does not accept formatting using the XMLFormat object. Also, XMLAgg does not enclose the output in an element tag as does SYS_XMLAgg. Within the order_by_clause, Oracle Database does not interpret number literals as column positions, as it does in other uses of this clause, but simply as number literals. Examples The following example produces a Department element containing Employee elements with employee job ID and last name as the contents of the elements: SELECT XMLELEMENT("Department", XMLAGG(XMLELEMENT("Employee", e.job_id||' '||e.last_name) ORDER BY last_name)) as "Dept_list" FROM employees e WHERE e.department_id = 30; Dept_list ------------------------------------------------------------- <Department> <Employee>PU_CLERK Baida</Employee> <Employee>PU_CLERK Colmenares</Employee> <Employee>PU_CLERK Himuro</Employee> <Employee>PU_CLERK Khoo</Employee> <Employee>PU_MAN Raphaely</Employee> <Employee>PU_CLERK Tobias</Employee> </Department> The result is a single row, because XMLAgg aggregates the rows. You can use the GROUP BY clause to group the returned set of rows into multiple groups: SELECT XMLELEMENT("Department", XMLAGG(XMLELEMENT("Employee", e.job_id||' '||e.last_name))) AS "Dept_list" FROM employees e GROUP BY e.department_id; See Also: XMLELEMENT on page 5-224 and SYS_XMLAGG on page 5-184 XMLAGG ( XMLType_instance order_by_clause )
- 382. XMLCDATA 5-220 Oracle Database SQL Reference Dept_list --------------------------------------------------------- <Department> <Employee>AD_ASST Whalen</Employee> </Department> <Department> <Employee>MK_MAN Hartstein</Employee> <Employee>MK_REP Fay</Employee> </Department> <Department> <Employee>PU_MAN Raphaely</Employee> <Employee>PU_CLERK Khoo</Employee> <Employee>PU_CLERK Tobias</Employee> <Employee>PU_CLERK Baida</Employee> <Employee>PU_CLERK Colmenares</Employee> <Employee>PU_CLERK Himuro</Employee> </Department> . . . XMLCDATA Syntax Purpose XMLCData generates a CDATA section by evaluating value_expr. The value_expr must resolve to a string. The value returned by the function takes the following form: <![CDATA[string]]> If the resulting value is not a valid XML CDATA section, then the function returns an error. The following conditions apply to XMLCData: ■ The value_expr cannot contain the substring ]]>. ■ If value_expr evaluates to null, then the function returns null. Examples The following statement uses the DUAL table to illustrate the syntax of XMLCData: SELECT XMLELEMENT("PurchaseOrder", XMLAttributes(dummy as "pono"), XMLCdata('<!DOCTYPE po_dom_group [ <!ELEMENT po_dom_group(student_name)*> <!ELEMENT po_purch_name (#PCDATA)> <!ATTLIST po_name po_no ID #REQUIRED> <!ATTLIST po_name trust_1 IDREF #IMPLIED> <!ATTLIST po_name trust_2 IDREF #IMPLIED> ]>')) "XMLCData" FROM DUAL; See Also: Oracle XML DB Developer's Guide for more information on this function XMLCDATA ( value_expr )
- 383. XMLCOLATTVAL Functions 5-221 XMLCData ---------------------------------------------------------- <PurchaseOrder pono="X"><![CDATA[ <!DOCTYPE po_dom_group [ <!ELEMENT po_dom_group(student_name)*> <!ELEMENT po_purch_name (#PCDATA)> <!ATTLIST po_name po_no ID #REQUIRED> <!ATTLIST po_name trust_1 IDREF #IMPLIED> <!ATTLIST po_name trust_2 IDREF #IMPLIED> ]> ]]> </PurchaseOrder> XMLCOLATTVAL Syntax Purpose XMLColAttVal creates an XML fragment and then expands the resulting XML so that each XML fragment has the name column with the attribute name. You can use the AS c_alias clause to change the value of the name attribute to something other than the column name. You must specify a value for value_expr. If value_expr is null, then no element is returned. Restriction on XMLColAttVal You cannot specify an object type column for value_ expr. Examples The following example creates an Emp element for a subset of employees, with nested employee_id, last_name, and salary elements as the contents of Emp. Each nested element is named column and has a name attribute with the column name as the attribute value: SELECT XMLELEMENT("Emp", XMLCOLATTVAL(e.employee_id, e.last_name, e.salary)) "Emp Element" FROM employees e WHERE employee_id = 204; Emp Element -------------------------------------------------------------------- <Emp> <column name="EMPLOYEE_ID">204</column> <column name="LAST_NAME">Baer</column> <column name="SALARY">10000</column> </Emp> Please refer to the example for XMLFOREST on page 5-226 to compare the output of these two functions. XMLCOLATTVAL ( value_expr AS c_alias , )
- 384. XMLCOMMENT 5-222 Oracle Database SQL Reference XMLCOMMENT Syntax Purpose XMLComment generates an XML comment using an evaluated result of value_expr. The value_expr must resolve to a string. It cannot contain two consecutive dashes (hyphens). The value returned by the function takes the following form: <!--string--> If value_expr resolves to null, then the function returns null. Examples The following example uses the DUAL table to illustrate the XMLComment syntax: SELECT XMLCOMMENT('OrderAnalysisComp imported, reconfigured, disassembled') AS "XMLCOMMENT" FROM DUAL; XMLCOMMENT -------------------------------------------------------------------------------- <!--OrderAnalysisComp imported, reconfigured, disassembled--> XMLCONCAT Syntax Purpose XMLConcat takes as input a series of XMLType instances, concatenates the series of elements for each row, and returns the concatenated series. XMLConcat is the inverse of XMLSequence. Null expressions are dropped from the result. If all the value expressions are null, then the function returns null. Examples The following example creates XML elements for the first and last names of a subset of employees, and then concatenates and returns those elements: SELECT XMLCONCAT(XMLELEMENT("First", e.first_name), XMLELEMENT("Last", e.last_name)) AS "Result" FROM employees e WHERE e.employee_id > 202; See Also: Oracle XML DB Developer's Guide for more information on this function See Also: XMLSEQUENCE on page 5-230 XMLCOMMENT ( value_expr ) XMLCONCAT ( XMLType_instance , )
- 385. XMLELEMENT Functions 5-223 Result ---------------------------------------------------------------- <First>Susan</First> <Last>Mavris</Last> <First>Hermann</First> <Last>Baer</Last> <First>Shelley</First> <Last>Higgins</Last> <First>William</First> <Last>Gietz</Last> 4 rows selected. XMLELEMENT Syntax XML_attributes_clause::= Purpose XMLElement takes an element name for identifier, an optional collection of attributes for the element, and arguments that make up the content of the element. It returns an instance of type XMLType. XMLElement is similar to SYS_XMLGen except that XMLElement can include attributes in the XML returned, but it does not accept formatting using the XMLFormat object. The XMLElement function is typically nested to produce an XML document with a nested structure, as in the example in the following section. You must specify a value for identifier, which Oracle Database uses as the enclosing tag. The identifier can be up to 4000 characters and does not have to be a column name or column reference. It cannot be an expression or null. The objects that make up the element content follow the XMLATTRIBUTES keyword. In the XML_attributes_clause, if the value_expr is null, then no attribute is created for that value expression. The type of value_expr cannot be an object type or collection. If you specify an alias for value_expr using the AS clause, the c_alias can be up to 4000 characters. For the optional value_expr that follows the XML_attributes_clause in the diagram: XMLELEMENT ( NAME identifier , XML_attributes_clause , value_expr AS c_alias ) XMLATTRIBUTES ( value_expr AS c_alias , )
- 386. XMLELEMENT 5-224 Oracle Database SQL Reference ■ If value_expr is a scalar expression, then you can omit the AS clause, and Oracle uses the column name as the element name. ■ If value_expr is an object type or collection, then the AS clause is mandatory, and Oracle uses the specified c_alias as the enclosing tag. ■ If value_expr is null, then no element is created for that value expression. Examples The following example produces an Emp element for a series of employees, with nested elements that provide the employee's name and hire date: SELECT XMLELEMENT("Emp", XMLELEMENT("Name", e.job_id||' '||e.last_name), XMLELEMENT("Hiredate", e.hire_date)) as "Result" FROM employees e WHERE employee_id > 200; Result ------------------------------------------------------------------- <Emp> <Name>MK_MAN Hartstein</Name> <Hiredate>17-FEB-96</Hiredate> </Emp> <Emp> <Name>MK_REP Fay</Name> <Hiredate>17-AUG-97</Hiredate> </Emp> <Emp> <Name>HR_REP Mavris</Name> <Hiredate>07-JUN-94</Hiredate> </Emp> <Emp> <Name>PR_REP Baer</Name> <Hiredate>07-JUN-94</Hiredate> </Emp> <Emp> <Name>AC_MGR Higgins</Name> <Hiredate>07-JUN-94</Hiredate> </Emp> <Emp> <Name>AC_ACCOUNT Gietz</Name> <Hiredate>07-JUN-94</Hiredate> </Emp> 6 rows selected. The following similar example uses the XMLElement function with the XML_ attributes_clause to create nested XML elements with attribute values for the top-level element: SELECT XMLELEMENT("Emp", XMLATTRIBUTES(e.employee_id AS "ID", e.last_name), XMLELEMENT("Dept", e.department_id), XMLELEMENT("Salary", e.salary)) AS "Emp Element" See Also: SYS_XMLGEN on page 5-185
- 387. XMLFOREST Functions 5-225 FROM employees e WHERE e.employee_id = 206; Emp Element --------------------------------------------------------------- <Emp ID="206" LAST_NAME="Gietz"> <Dept>110</Dept> <Salary>8300</Salary> </Emp> Notice that the AS identifier clause was not specified for the last_name column. As a result, the XML returned uses the column name last_name as the default. Finally, the next example uses a subquery within the XML_attributes_clause to retrieve information from another table into the attributes of an element: SELECT XMLELEMENT("Emp", XMLATTRIBUTES(e.employee_id, e.last_name), XMLELEMENT("Dept", XMLATTRIBUTES(e.department_id, (SELECT d.department_name FROM departments d WHERE d.department_id = e.department_id) as "Dept_name")), XMLELEMENT("salary", e.salary), XMLELEMENT("Hiredate", e.hire_date)) AS "Emp Element" FROM employees e WHERE employee_id = 205; Emp Element ------------------------------------------------------------------- <Emp EMPLOYEE_ID="205" LAST_NAME="Higgins"> <Dept DEPARTMENT_ID="110" Dept_name="Accounting"/> <salary>12000</salary> <Hiredate>07-JUN-94</Hiredate> </Emp> XMLFOREST Syntax Purpose XMLForest converts each of its argument parameters to XML, and then returns an XML fragment that is the concatenation of these converted arguments. ■ If value_expr is a scalar expression, then you can omit the AS clause, and Oracle Database uses the column name as the element name. ■ If value_expr is an object type or collection, then the AS clause is mandatory, and Oracle uses the specified c_alias as the enclosing tag. The c_alias can be up to 4000 characters. ■ If value_expr is null, then no element is created for that value_expr. Examples The following example creates an Emp element for a subset of employees, with nested employee_id, last_name, and salary elements as the contents of Emp: XMLFOREST ( value_expr AS c_alias , )
- 388. XMLPARSE 5-226 Oracle Database SQL Reference SELECT XMLELEMENT("Emp", XMLFOREST(e.employee_id, e.last_name, e.salary)) "Emp Element" FROM employees e WHERE employee_id = 204; Emp Element ---------------------------------------------------------------- <Emp> <EMPLOYEE_ID>204</EMPLOYEE_ID> <LAST_NAME>Baer</LAST_NAME> <SALARY>10000</SALARY> </Emp> Please refer to the example for XMLCOLATTVAL on page 5-222 to compare the output of these two functions. XMLPARSE Syntax Purpose XMLParse parses and generates an XML instance from the evaluated result of value_ expr. The value_expr must resolve to a string. If value_expr resolves to null, then the function returns null. ■ If you specify DOCUMENT, then value_expr must resolve to a singly rooted XML document. ■ If you specify CONTENT, then value_expr must resolve to a valid XML value. ■ When you specify WELLFORMED, you are guaranteeing that value_expr resolves to a well-formed XML document, so the database does not perform validity checks to ensure that the input is well formed. Examples The following example uses the DUAL table to illustrate the syntax of XMLParse: SELECT XMLPARSE(CONTENT '124 <purchaseOrder poNo="12435"> <customerName> Acme Enterprises</customerName> <itemNo>32987457</itemNo> </purchaseOrder>' WELLFORMED) AS PO FROM DUAL; PO ----------------------------------------------------------------- 124 <purchaseOrder poNo="12435"> <customerName> Acme Enterprises</customerName> <itemNo>32987457</itemNo> </purchaseOrder> See Also: Oracle XML DB Developer's Guide for more information on this function XMLPARSE ( DOCUMENT CONTENT value_expr WELLFORMED )
- 389. XMLQUERY Functions 5-227 XMLPI Syntax Purpose XMLPI generates an XML processing instruction using identifier and optionally the evaluated result of value_expr. A processing instruction is commonly used to provide to an application information that is associated with all or part of an XML document. The application uses the processing instruction to determine how best to process the XML document. The optional value_expr must resolve to a string. If you omit value_expr, then a zero-length string is the default. The value returned by the function takes this form: <?identifier string?> XMLPI is subject to the following restrictions: ■ The identifier must be a valid target for a processing instruction. ■ You cannot specify xml in any case combination for identifier. ■ The identifier cannot contain the consecutive characters ?>. Examples The following statement uses the DUAL table to illustrate the use of the XMLPI syntax: SELECT XMLPI(NAME "Order analysisComp", 'imported, reconfigured, disassembled') AS "XMLPI" FROM DUAL; XMLPI -------------------------------------------------------------------------------- <?Order analysisComp imported, reconfigured, disassembled?> The following fragment instructs the application (for example, a browser) to display the XML document using the cascading stylesheet test.css: <?xml-stylesheet type="text/css" href="test.css"?> XMLQUERY Syntax See Also: Oracle XML DB Developer's Guide for more information on this function XMLPI ( NAME identifier , value_expr ) XMLQUERY ( XQuery_string XML_passing_clause RETURNING CONTENT )
- 390. XMLQUERY 5-228 Oracle Database SQL Reference XML_passing_clause::= Purpose XMLQUERY lets you query XML data in SQL statements. It takes an XQuery expression as a string literal, an optional context item, and other bind variables and returns the result of evaluating the XQuery expression using these input values. ■ XQuery_string is a complete XQuery expression, including prolog. ■ The expr in the XML_passing_clause is an expression returning an XMLType that is used as the context for evaluating the XQuery expression. You can specify only one expr in the PASSING clause without an identifier. The result of evaluating each expr is bound to the corresponding identifier in the XQuery_ string. If any expr that is not followed by an AS clause, then the result of evaluating that expression is used as the context item for evaluating the XQuery_ string. ■ RETURNING CONTENT indicates that the result from the XQuery evaluation is either an XML 1.0 document or a document fragment conforming to the XML 1.0 semantics. Examples The following statement specifies the warehouse_spec column of the oe.warehouses table in the XML_passing_clause as a context item. The statement returns specific information about the warehouses with area greater than 50K. SELECT warehouse_name, EXTRACTVALUE(warehouse_spec, ’/Warehouse/Area’), XMLQuery( 'for $i in /Warehouse where $i/Area > 50000 return <Details> <Docks num="{$i/Docks}"/> <Rail> { if ($i/RailAccess = "Y") then "true" else "false" } </Rail> </Details>' PASSING warehouse_spec RETURNING CONTENT) "Big_warehouses" FROM warehouses; WAREHOUSE_ID Area Big_warehouses ------------ --------- -------------------------------------------------------- 1 25000 2 50000 3 85700 <Details><Docks></Docks><Rail>false</Rail></Details> 4 103000 <Details><Docks num="3"></Docks><Rail>true</Rail></Details> . . . See Also: Oracle XML DB Developer's Guide for more information on this function PASSING BY VALUE expr AS identifier ,
- 391. XMLSEQUENCE Functions 5-229 XMLROOT Syntax Purpose XMLROOT lets you create a new XML value by providing version and standalone properties in the XML root information (prolog) of an existing XML value. If the value_expr already has a prolog, then the database returns an error. If the input is null, then the function returns null. The value returned takes the following form: <?xml version = "version" [ STANDALONE = "{yes | no}" ]?> ■ The first value_expr specifies the XML value for which you are providing prolog information. ■ In the VERSION clause, value_expr must resolve to a string representing a valid XML version. If you specify NO VALUE for VERSION, then the version defaults to 1.0. ■ If you omit the optional STANDALONE clause, or if you specify it with NO VALUE, then the standalone property is absent from the value returned by the function. Examples The following statement uses the DUAL table to illustrate the syntax of XMLROOT: SELECT XMLROOT ( XMLType('<poid>143598</poid>'), VERSION '1.0', STANDALONE YES) AS "XMLROOT" FROM DUAL; XMLROOT -------------------------------------------------------------------------------- <?xml version="1.0" standalone="yes"?> <poid>143598</poid> XMLSEQUENCE Syntax Purpose XMLSequence has two forms: ■ The first form takes as input an XMLType instance and returns a varray of the top-level nodes in the XMLType. This form is effectively superseded by the XMLROOT ( value_expr , VERSION value_expr NO VALUE , STANDALONE YES NO NO VALUE ) XMLSEQUENCE ( XMLType_instance sys_refcursor_instance , fmt )
- 392. XMLSEQUENCE 5-230 Oracle Database SQL Reference SQL/XML standard function XMLTable, which provides for more readable SQL code. Prior to Oracle Database 10g Release 2, XMLSequence was used with SQL function TABLE to do some of what can now be done better with the XMLTable function. ■ The second form takes as input a REFCURSOR instance, with an optional instance of the XMLFormat object, and returns as an XMLSequence type an XML document for each row of the cursor. Because XMLSequence returns a collection of XMLType, you can use this function in a TABLE clause to unnest the collection values into multiple rows, which can in turn be further processed in the SQL query. Examples The following example shows how XMLSequence divides up an XML document with multiple elements into VARRAY single-element documents. In this example, the TABLE keyword instructs Oracle Database to consider the collection a table value that can be used in the FROM clause of the subquery: SELECT EXTRACT(warehouse_spec, '/Warehouse') as "Warehouse" FROM warehouses WHERE warehouse_name = 'San Francisco'; Warehouse ------------------------------------------------------------ <Warehouse> <Building>Rented</Building> <Area>50000</Area> <Docks>1</Docks> <DockType>Side load</DockType> <WaterAccess>Y</WaterAccess> <RailAccess>N</RailAccess> <Parking>Lot</Parking> <VClearance>12 ft</VClearance> </Warehouse> 1 row selected. SELECT VALUE(p) FROM warehouses w, TABLE(XMLSEQUENCE(EXTRACT(warehouse_spec, '/Warehouse/*'))) p WHERE w.warehouse_name = 'San Francisco'; VALUE(P) ---------------------------------------------------------------- <Building>Rented</Building> <Area>50000</Area> <Docks>1</Docks> <DockType>Side load</DockType> <WaterAccess>Y</WaterAccess> <RailAccess>N</RailAccess> <Parking>Lot</Parking> <VClearance>12 ft</VClearance> 8 rows selected. See Also: Oracle XML DB Developer's Guide for more information on this function, and XMLTABLE on page 5-232
- 393. XMLTABLE Functions 5-231 XMLSERIALIZE Syntax Purpose XMLSerialize creates a string or LOB containing the contents of value_expr. ■ If you specify DOCUMENT, then the value_expr must be a valid XML document. ■ If you specify CONTENT, then the value_expr need not be a singly rooted XML document. However it must be valid XML content. ■ The datatype specified can be a string type (VARCHAR2 or VARCHAR, but not NVARCHAR or NVARCHAR2) or CLOB . The default is CLOB. Examples The following statement uses the DUAL table to illustrate the syntax of XMLSerialize: SELECT XMLSERIALIZE(CONTENT XMLTYPE(’<Owner>Grandco</Owner>’)) FROM DUAL; XMLTABLE Syntax XML_namespaces_clause::= XMLTABLE_options::= XML_passing_clause::= See Also: Oracle XML DB Developer's Guide for more information on this function XMLSERIALIZE ( DOCUMENT CONTENT value_expr AS datatype ) XMLTABLE ( XML_namespaces_clause , XQuery_string XMLTABLE_options ) XMLNAMESPACES ( string AS identifier , DEFAULT string ) XML_passing_clause COLUMNS XML_table_column , PASSING BY VALUE expr AS identifier ,
- 394. XMLTABLE 5-232 Oracle Database SQL Reference XML_table_column::= Purpose XMLTable maps the result of an XQuery evaluation into relational rows and columns. You can query the result returned by the function as a virtual relational table using SQL. ■ The XMLNAMESPACES clause contains a set of XML namespace declarations. These declarations are referenced by the XQuery expression (the evaluated XQuery_ string), which computes the row, and by the XPath expression in the PATH clause of XML_table_column, which computes the columns for the entire XMLTable function. If you want to use qualified names in the PATH expressions of the COLUMNS clause, then you need to specify the XMLNAMESPACES clause. ■ XQuery_string is a complete XQuery expression and can include prolog declarations. ■ The expr in the XML_passing_clause is an expression returning an XMLType that is used as the context for evaluating the XQuery expression. You can specify only one expr in the PASSING clause without an identifier. The result of evaluating each expr is bound to the corresponding identifier in the XQuery_ string. If any expr that is not followed by an AS clause, then the result of evaluating that expression is used as the context item for evaluating the XQuery_ string. ■ The optional COLUMNS clause defines the columns of the virtual table to be created by XMLTable. – If you omit the COLUMNS clause, then XMLTable returns a row with a single XMLType pseudocolumn named COLUMN_VALUE. – FOR ORDINALITY specifies that column is to be a column of generated row numbers. There must be at most one FOR ORDINALITY clause. It is created as a NUMBER column. – The optional PATH clause specifies that the portion of the XQuery result that is addressed by XPath expression string is to be used as the column content. If you omit PATH, then the XPath expression column is assumed. For example: XMLTable(... COLUMNS xyz is equivalent to XMLTable(... COLUMNS xyz PATH ’XYZ’) You can use different PATH clauses to split the XQuery result into different virtual-table columns. – The optional DEFAULT clause specifies the value to use when the PATH expression results in an empty sequence. Its expr is an XQuery expression that is evaluated to produce the default value. See Also: Oracle XML DB Developer's Guide for more information on the XMLTable function, including additional examples, and on XQuery in general column FOR ORDINALITY datatype PATH string DEFAULT expr
- 395. XMLTRANSFORM Functions 5-233 Examples The following example converts the result of applying the XQuery '/Warehouse' to each value in the warehouse_spec column of the warehouses table into a virtual relational table with columns Water and Rail: SELECT warehouse_name warehouse, warehouse2."Water", warehouse2."Rail" FROM warehouses, XMLTABLE('/Warehouse' PASSING warehouses.warehouse_spec COLUMNS "Water" varchar2(6) PATH '/Warehouse/WaterAccess', "Rail" varchar2(6) PATH '/Warehouse/RailAccess') warehouse2; WAREHOUSE Water Rail ----------------------------------- ------ ------ Southlake, Texas Y N San Francisco Y N New Jersey N N Seattle, Washington N Y XMLTRANSFORM Syntax Purpose XMLTransform takes as arguments an XMLType instance and an XSL style sheet, which is itself a form of XMLType instance. It applies the style sheet to the instance and returns an XMLType. This function is useful for organizing data according to a style sheet as you are retrieving it from the database. Examples The XMLTransform function requires the existence of an XSL style sheet. Here is an example of a very simple style sheet that alphabetizes elements within a node: CREATE TABLE xsl_tab (col1 XMLTYPE); INSERT INTO xsl_tab VALUES ( XMLTYPE.createxml( '<?xml version="1.0"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" > <xsl:output encoding="utf-8"/> <!-- alphabetizes an xml tree --> <xsl:template match="*"> <xsl:copy> <xsl:apply-templates select="*|text()"> <xsl:sort select="name(.)" data-type="text" order="ascending"/> </xsl:apply-templates> See Also: Oracle XML DB Developer's Guide for more information on this function XMLTRANSFORM ( XMLType_instance , XMLType_instance )
- 396. ROUND and TRUNC Date Functions 5-234 Oracle Database SQL Reference </xsl:copy> </xsl:template> <xsl:template match="text()"> <xsl:value-of select="normalize-space(.)"/> </xsl:template> </xsl:stylesheet> ')); 1 row created. The next example uses the xsl_tab XSL style sheet to alphabetize the elements in one warehouse_spec of the sample table oe.warehouses: SELECT XMLTRANSFORM(w.warehouse_spec, x.col1).GetClobVal() FROM warehouses w, xsl_tab x WHERE w.warehouse_name = 'San Francisco'; XMLTRANSFORM(W.WAREHOUSE_SPEC,X.COL1).GETCLOBVAL() -------------------------------------------------------------------------------- <Warehouse> <Area>50000</Area> <Building>Rented</Building> <DockType>Side load</DockType> <Docks>1</Docks> <Parking>Lot</Parking> <RailAccess>N</RailAccess> <VClearance>12 ft</VClearance> <WaterAccess>Y</WaterAccess> </Warehouse> ROUND and TRUNC Date Functions Table 5–14 lists the format models you can use with the ROUND and TRUNC date functions and the units to which they round and truncate dates. The default model, 'DD', returns the date rounded or truncated to the day with a time of midnight. Table 5–14 Date Format Models for the ROUND and TRUNC Date Functions Format Model Rounding or Truncating Unit CC SCC One greater than the first two digits of a four-digit year SYYYY YYYY YEAR SYEAR YYY YY Y Year (rounds up on July 1) IYYY IY IY I ISO Year Q Quarter (rounds up on the sixteenth day of the second month of the quarter) MONTH MON MM RM Month (rounds up on the sixteenth day)
- 397. User-Defined Functions Functions 5-235 The starting day of the week used by the format models DAY, DY, and D is specified implicitly by the initialization parameter NLS_TERRITORY. User-Defined Functions You can write user-defined functions in PL/SQL or Java to provide functionality that is not available in SQL or SQL built-in functions. User-defined functions can appear in a SQL statement anywhere SQL functions can appear, that is, wherever an expression can occur. For example, user-defined functions can be used in the following: ■ The select list of a SELECT statement ■ The condition of a WHERE clause ■ CONNECT BY, START WITH, ORDER BY, and GROUP BY clauses ■ The VALUES clause of an INSERT statement ■ The SET clause of an UPDATE statement WW Same day of the week as the first day of the year IW Same day of the week as the first day of the ISO year W Same day of the week as the first day of the month DDD DD J Day DAY DY D Starting day of the week HH HH12 HH24 Hour MI Minute See Also: Oracle Database Reference and Oracle Database Globalization Support Guide for information on this parameter Note: Oracle SQL does not support calling of functions with Boolean parameters or returns. Therefore, if your user-defined functions will be called from SQL statements, you must design them to return numbers (0 or 1) or character strings (’TRUE’ or ’FALSE’). Table 5–14 (Cont.) Date Format Models for the ROUND and TRUNC Date Functions Format Model Rounding or Truncating Unit
- 398. Prerequisites 5-236 Oracle Database SQL Reference user_defined_function::= The optional expression list must match attributes of the function, package, or operator. Restriction on User-defined Functions The DISTINCT and ALL keywords are valid only with a user-defined aggregate function. Prerequisites User-defined functions must be created as top-level functions or declared with a package specification before they can be named within a SQL statement. To use a user function in a SQL expression, you must own or have EXECUTE privilege on the user function. To query a view defined with a user function, you must have SELECT privileges on the view. No separate EXECUTE privileges are needed to select from the view. Name Precedence Within a SQL statement, the names of database columns take precedence over the names of functions with no parameters. For example, if the Human Resources manager creates the following two objects in the hr schema: CREATE TABLE new_emps (new_sal NUMBER, ...); CREATE FUNCTION new_sal RETURN NUMBER IS BEGIN ... END; then in the following two statements, the reference to new_sal refers to the column new_emps.new_sal: SELECT new_sal FROM new_emps; SELECT new_emps.new_sal FROM new_emps; To access the function new_sal, you would enter: SELECT hr.new_sal FROM new_emps; Here are some sample calls to user functions that are allowed in SQL expressions: See Also: ■ CREATE FUNCTION on page 14-48 for information on creating functions, including restrictions on user-defined functions ■ Oracle Database Application Developer's Guide - Fundamentals for a complete discussion of the creation and use of user functions See Also: CREATE FUNCTION on page 14-48 for information on creating top-level functions and CREATE PACKAGE on page 15-39 for information on specifying packaged functions schema . package . function user_defined_operator @ dblink . ( DISTINCT ALL expr , )
- 399. User-Defined Functions Functions 5-237 circle_area (radius) payroll.tax_rate (empno) hr.employees.tax_rate (dependent, empno)@remote Example To call the tax_rate user function from schema hr, execute it against the ss_no and sal columns in tax_table, specify the following: SELECT hr.tax_rate (ss_no, sal) INTO income_tax FROM tax_table WHERE ss_no = tax_id; The INTO clause is PL/SQL that lets you place the results into the variable income_ tax. Naming Conventions If only one of the optional schema or package names is given, then the first identifier can be either a schema name or a package name. For example, to determine whether PAYROLL in the reference PAYROLL.TAX_RATE is a schema or package name, Oracle Database proceeds as follows: 1. Check for the PAYROLL package in the current schema. 2. If a PAYROLL package is not found, then look for a schema name PAYROLL that contains a top-level TAX_RATE function. If no such function is found, then return an error. 3. If the PAYROLL package is found in the current schema, then look for a TAX_RATE function in the PAYROLL package. If no such function is found, then return an error. You can also refer to a stored top-level function using any synonym that you have defined for it.
- 400. Name Precedence 5-238 Oracle Database SQL Reference
- 401. Expressions 6-1 6 Expressions This chapter describes how to combine values, operators, and functions into expressions. This chapter includes these sections: ■ About SQL Expressions ■ Simple Expressions ■ Compound Expressions ■ CASE Expressions ■ CURSOR Expressions ■ Datetime Expressions ■ Function Expressions ■ Interval Expressions ■ Object Access Expressions ■ Scalar Subquery Expressions ■ Model Expressions ■ Type Constructor Expressions ■ Variable Expressions ■ Expression Lists About SQL Expressions An expression is a combination of one or more values, operators, and SQL functions that evaluates to a value. An expression generally assumes the datatype of its components.
- 402. About SQL Expressions 6-2 Oracle Database SQL Reference This simple expression evaluates to 4 and has datatype NUMBER (the same datatype as its components): 2*2 The following expression is an example of a more complex expression that uses both functions and operators. The expression adds seven days to the current date, removes the time component from the sum, and converts the result to CHAR datatype: TO_CHAR(TRUNC(SYSDATE+7)) You can use expressions in: ■ The select list of the SELECT statement ■ A condition of the WHERE clause and HAVING clause ■ The CONNECT BY, START WITH, and ORDER BY clauses ■ The VALUES clause of the INSERT statement ■ The SET clause of the UPDATE statement For example, you could use an expression in place of the quoted string 'Smith' in this UPDATE statement SET clause: SET last_name = 'Smith'; This SET clause has the expression INITCAP(last_name) instead of the quoted string 'Smith': SET last_name = INITCAP(last_name); Expressions have several forms, as shown in the following syntax: Note: The combined values of the NLS_COMP and NLS_SORT settings determine the rules by which characters are sorted and compared. If NLS_COMP is set to LINGUISTIC for your database, then all entities in this chapter will be interpreted according to the rules specified by the NLS_SORT parameter. If NLS_COMP is not set to LINGUISTIC, then the functions are interpreted without regard to the NLS_SORT setting. NLS_SORT can be explicitly set. If it is not set explicitly, it is derived from NLS_LANGUAGE. Please refer to Oracle Database Globalization Support Guide for more information on these settings.
- 403. Simple Expressions Expressions 6-3 expr::= Oracle Database does not accept all forms of expressions in all parts of all SQL statements. Please refer to the individual SQL statements in Chapter 10 through Chapter 19 for information on restrictions on the expressions in that statement. You must use appropriate expression notation whenever expr appears in conditions, SQL functions, or SQL statements in other parts of this reference. The sections that follow describe and provide examples of the various forms of expressions. Simple Expressions A simple expression specifies a column, pseudocolumn, constant, sequence number, or null. simple_expression::= simple_expression compound_expression case_expression cursor_expression datetime_expression function_expression interval_expression object_access_expression scalar_subquery_expression model_expression type_constructor_expression variable_expression query_name schema table view materialized view . column ROWID ROWNUM string number sequence . CURRVAL NEXTVAL NULL
- 404. Compound Expressions 6-4 Oracle Database SQL Reference In addition to the schema of a user, schema can also be "PUBLIC" (double quotation marks required), in which case it must qualify a public synonym for a table, view, or materialized view. Qualifying a public synonym with "PUBLIC" is supported only in data manipulation language (DML) statements, not data definition language (DDL) statements. You can specify ROWID only with a table, not with a view or materialized view. NCHAR and NVARCHAR2 are not valid pseudocolumn datatypes. Some valid simple expressions are: employees.last_name 'this is a text string' 10 N'this is an NCHAR string' Compound Expressions A compound expression specifies a combination of other expressions. compound_expression::= You can use any built-in function as an expression ("Function Expressions" on page 6-9). However, in a compound expression, some combinations of functions are inappropriate and are rejected. For example, the LENGTH function is inappropriate within an aggregate function. The PRIOR operator is used in CONNECT BY clauses of hierarchical queries. Some valid compound expressions are: ('CLARK' || 'SMITH') LENGTH('MOOSE') * 57 SQRT(144) + 72 my_fun(TO_CHAR(sysdate,'DD-MMM-YY')) See Also: Chapter 3, "Pseudocolumns" for more information on pseudocolumns and subquery_factoring_clause on page 19-11 for information on query_name See Also: "Operator Precedence" on page 4-2 and "Hierarchical Queries" on page 9-2 ( expr ) + – PRIOR expr expr * / + – | | expr
- 405. CASE Expressions Expressions 6-5 CASE Expressions CASE expressions let you use IF ... THEN ... ELSE logic in SQL statements without having to invoke procedures. The syntax is: simple_case_expression::= searched_case_expression::= else_clause::= In a simple CASE expression, Oracle Database searches for the first WHEN ... THEN pair for which expr is equal to comparison_expr and returns return_expr. If none of the WHEN ... THEN pairs meet this condition, and an ELSE clause exists, then Oracle returns else_expr. Otherwise, Oracle returns null. You cannot specify the literal NULL for every return_expr and the else_expr. In a searched CASE expression, Oracle searches from left to right until it finds an occurrence of condition that is true, and then returns return_expr. If no condition is found to be true, and an ELSE clause exists, Oracle returns else_expr. Otherwise, Oracle returns null. Oracle Database uses short-circuit evaluation. That is, for a simple CASE expression, the database evaluates each comparison_expr value only before comparing it to expr, rather than evaluating all comparison_expr values before comparing any of them with expr. Consequently, Oracle never evaluates a comparison_expr if a previous comparison_expr is equal to expr. For a searched CASE expression, the database evaluates each condition to determine whether it is true, and never evaluates a condition if the previous condition was true. For a simple CASE expression, the expr and all comparison_expr values must either have the same datatype (CHAR, VARCHAR2, NCHAR, or NVARCHAR2, NUMBER, BINARY_FLOAT, or BINARY_DOUBLE) or must all have a numeric datatype. If all expressions have a numeric datatype, then Oracle determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype, and returns that datatype. For both simple and searched CASE expressions, all of the return_exprs must either have the same datatype (CHAR, VARCHAR2, NCHAR, or NVARCHAR2, NUMBER, BINARY_ FLOAT, or BINARY_DOUBLE) or must all have a numeric datatype. If all return expressions have a numeric datatype, then Oracle determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype, and returns that datatype. The maximum number of arguments in a CASE expression is 255. All expressions count toward this limit, including the initial expression of a simple CASE expression CASE simple_case_expression searched_case_expression else_clause END expr WHEN comparison_expr THEN return_expr WHEN condition THEN return_expr ELSE else_expr
- 406. CURSOR Expressions 6-6 Oracle Database SQL Reference and the optional ELSE expression. Each WHEN ... THEN pair counts as two arguments. To avoid exceeding this limit, you can nest CASE expressions so that the return_ expr itself is a CASE expression. Simple CASE Example For each customer in the sample oe.customers table, the following statement lists the credit limit as "Low" if it equals $100, "High" if it equals $5000, and "Medium" if it equals anything else. SELECT cust_last_name, CASE credit_limit WHEN 100 THEN 'Low' WHEN 5000 THEN 'High' ELSE 'Medium' END FROM customers; CUST_LAST_NAME CASECR -------------------- ------ ... Bogart Medium Nolte Medium Loren Medium Gueney Medium Searched CASE Example The following statement finds the average salary of the employees in the sample table oe.employees, using $2000 as the lowest salary possible: SELECT AVG(CASE WHEN e.salary > 2000 THEN e.salary ELSE 2000 END) "Average Salary" FROM employees e; Average Salary -------------- 6461.68224 CURSOR Expressions A CURSOR expression returns a nested cursor. This form of expression is equivalent to the PL/SQL REF CURSOR and can be passed as a REF CURSOR argument to a function. A nested cursor is implicitly opened when the cursor expression is evaluated. For example, if the cursor expression appears in a select list, a nested cursor will be opened for each row fetched by the query. The nested cursor is closed only when: ■ The nested cursor is explicitly closed by the user See Also: ■ Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion ■ "Numeric Precedence" on page 2-13 for information on numeric precedence ■ COALESCE on page 5-34 and NULLIF on page 5-107 for alternative forms of CASE logic ■ Oracle Database Data Warehousing Guide for examples using various forms of the CASE expression CURSOR ( subquery )
- 407. CURSOR Expressions Expressions 6-7 ■ The parent cursor is reexecuted ■ The parent cursor is closed ■ The parent cursor is cancelled ■ An error arises during fetch on one of its parent cursors (it is closed as part of the clean-up) Restrictions on CURSOR Expressions The following restrictions apply to CURSOR expressions: ■ If the enclosing statement is not a SELECT statement, nested cursors can appear only as REF CURSOR arguments of a procedure. ■ If the enclosing statement is a SELECT statement, nested cursors can also appear in the outermost select list of the query specification or in the outermost select list of another nested cursor. ■ Nested cursors cannot appear in views. ■ You cannot perform BIND and EXECUTE operations on nested cursors. Examples The following example shows the use of a CURSOR expression in the select list of a query: SELECT department_name, CURSOR(SELECT salary, commission_pct FROM employees e WHERE e.department_id = d.department_id) FROM departments d; The next example shows the use of a CURSOR expression as a function argument. The example begins by creating a function in the sample OE schema that can accept the REF CURSOR argument. (The PL/SQL function body is shown in italics.) CREATE FUNCTION f(cur SYS_REFCURSOR, mgr_hiredate DATE) RETURN NUMBER IS emp_hiredate DATE; before number :=0; after number:=0; begin loop fetch cur into emp_hiredate; exit when cur%NOTFOUND; if emp_hiredate > mgr_hiredate then after:=after+1; else before:=before+1; end if; end loop; close cur; if before > after then return 1; else return 0; end if; end; / The function accepts a cursor and a date. The function expects the cursor to be a query returning a set of dates. The following query uses the function to find those managers
- 408. Datetime Expressions 6-8 Oracle Database SQL Reference in the sample employees table, most of whose employees were hired before the manager. SELECT e1.last_name FROM employees e1 WHERE f( CURSOR(SELECT e2.hire_date FROM employees e2 WHERE e1.employee_id = e2.manager_id), e1.hire_date) = 1; LAST_NAME ------------------------- De Haan Mourgos Cambrault Zlotkey Higgens Datetime Expressions A datetime expression yields a value of one of the datetime datatypes. datetime_expression::= A datetime_value_expr can be a datetime column or a compound expression that yields a datetime value. Datetimes and intervals can be combined according to the rules defined in Table 2–5 on page 2-20. The three combinations that yield datetime values are valid in a datetime expression. If you specify AT LOCAL, Oracle uses the current session time zone. The settings for AT TIME ZONE are interpreted as follows: ■ The string '(+|-)HH:MM' specifies a time zone as an offset from UTC. ■ DBTIMEZONE: Oracle uses the database time zone established (explicitly or by default) during database creation. ■ SESSIONTIMEZONE: Oracle uses the session time zone established by default or in the most recent ALTER SESSION statement. ■ time_zone_name: Oracle returns the datetime_value_expr in the time zone indicated by time_zone_name. For a listing of valid time zone names, query the V$TIMEZONE_NAMES dynamic performance view. datetime_value_expr AT LOCAL TIME ZONE ’ + – hh : mm ’ DBTIMEZONE SESSIONTIMEZONE ’ time_zone_name ’ expr
- 409. Function Expressions Expressions 6-9 ■ expr: If expr returns a character string with a valid time zone format, Oracle returns the input in that time zone. Otherwise, Oracle returns an error. Example The following example converts the datetime value of one time zone to another time zone: SELECT FROM_TZ(CAST(TO_DATE('1999-12-01 11:00:00', 'YYYY-MM-DD HH:MI:SS') AS TIMESTAMP), 'America/New_York') AT TIME ZONE 'America/Los_Angeles' "West Coast Time" FROM DUAL; West Coast Time ------------------------------------------------ 01-DEC-99 08.00.00.000000 AM AMERICA/LOS_ANGELES Function Expressions You can use any built-in SQL function or user-defined function as an expression. Some valid built-in function expressions are: LENGTH('BLAKE') ROUND(1234.567*43) SYSDATE A user-defined function expression specifies a call to: ■ A function in an Oracle-supplied package (see Oracle Database PL/SQL Packages and Types Reference) ■ A function in a user-defined package or type or in a standalone user-defined function (see "User-Defined Functions" on page 5-236) ■ A user-defined function or operator (see CREATE OPERATOR on page 15-32, CREATE FUNCTION on page 14-48, and Oracle Database Data Cartridge Developer's Guide) Note: Timezone region names are needed by the daylight savings feature. The region names are stored in two time zone files. The default time zone file is a small file containing only the most common time zones to maximize performance. If your time zone is not in the default file, then you will not have daylight savings support until you provide a path to the complete (larger) file by way of the ORA_TZFILE environment variable. See Also: ■ Oracle Database Administrator's Guide for more information about setting the ORA_TZFILE environment variable ■ Oracle Database Globalization Support Guide. for a complete listing of the timezone region names in both files ■ Oracle Database Reference for information on the dynamic performance views See Also: "SQL Functions" on page 5-1 and "Aggregate Functions" on page 5-8 for information on built-in functions
- 410. Interval Expressions 6-10 Oracle Database SQL Reference Some valid user-defined function expressions are: circle_area(radius) payroll.tax_rate(empno) hr.employees.comm_pct(dependents, empno)@remote DBMS_LOB.getlength(column_name) my_function(DISTINCT a_column) Restriction on User-Defined Function Expressions You cannot pass arguments of object type or XMLType to remote functions and procedures. Interval Expressions An interval expression yields a value of INTERVAL YEAR TO MONTH or INTERVAL DAY TO SECOND. interval_expression::= The interval_value_expr can be the value of an INTERVAL column or a compound expression that yields an interval value. Datetimes and intervals can be combined according to the rules defined in Table 2–5 on page 2-20. The six combinations that yield interval values are valid in an interval expression. Both leading_field_precision and fractional_second_precision can be any integer from 0 to 9. If you omit the leading_field_precision for either DAY or YEAR, then Oracle Database uses the default value of 2. If you omit the fractional_second_precision for second, then the database uses the default value of 6. If the value returned by a query contains more digits that the default precision, then Oracle Database returns an error. Therefore, it is good practice to specify a precision that you know will be at least as large as any value returned by the query. For example, the following statement subtracts the value of the order_date column in the sample table orders (a datetime value) from the system timestamp (another datetime value) to yield an interval value expression. Because we do not know how many days ago the oldest order was placed, we specify the maximum value of 9 for the DAY lading field precision: SELECT (SYSTIMESTAMP - order_date) DAY(9) TO SECOND FROM orders WHERE order_id = 2458; Object Access Expressions An object access expression specifies attribute reference and method invocation. interval_value_expr DAY ( leading_field_precision ) TO SECOND ( fractional_second_precision ) YEAR ( leading_field_precision ) TO MONTH
- 411. Model Expressions Expressions 6-11 object_access_expression::= The column parameter can be an object or REF column. If you specify expr, it must resolve to an object type. When a type's member function is invoked in the context of a SQL statement, if the SELF argument is null, Oracle returns null and the function is not invoked. Examples The following example creates a table based on the sample oe.order_ item_typ object type, and then shows how you would update and select from the object column attributes. CREATE TABLE short_orders ( sales_rep VARCHAR2(25), item order_item_typ); UPDATE short_orders s SET sales_rep = 'Unassigned'; SELECT o.item.line_item_id, o.item.quantity FROM short_orders o; Scalar Subquery Expressions A scalar subquery expression is a subquery that returns exactly one column value from one row. The value of the scalar subquery expression is the value of the select list item of the subquery. If the subquery returns 0 rows, then the value of the scalar subquery expression is NULL. If the subquery returns more than one row, then Oracle returns an error. You can use a scalar subquery expression in most syntax that calls for an expression (expr). However, scalar subqueries are not valid expressions in the following places: ■ As default values for columns ■ As hash expressions for clusters ■ In the RETURNING clause of DML statements ■ As the basis of a function-based index ■ In CHECK constraints ■ In WHEN conditions of CASE expressions ■ In GROUP BY and HAVING clauses ■ In START WITH and CONNECT BY clauses ■ In statements that are unrelated to queries, such as CREATE PROFILE Model Expressions A model expression is used only in the model_clause of a SELECT statement and then only on the right-hand side of a model rule. It yields a value for a cell in a table_alias . column . object_table_alias . ( expr ) . attribute . . method ( argument , ) method ( argument , )
- 412. Model Expressions 6-12 Oracle Database SQL Reference measure column previously defined in the model_clause. For additional information, please refer to model_clause on page 19-23. model_expression::= When you specify a measure column in a model expression, any conditions and expressions you specify must resolve to single values. When you specify an aggregate function in a model expression, the argument to the function is a measure column that has been previously defined in the model_clause. An aggregate function can be used only on the right-hand side of a model rule. Specifying an analytic function on the right-hand side of the model rule lets you express complex calculations directly in the model_clause. The following restrictions apply when using an analytic function in a model expression: ■ Analytic functions can be used only in an UPDATE rule. ■ You cannot specify an analytic function on the right-hand side of the model rule if the left-hand side of the rule contains a FOR loop or an ORDER BY clause. ■ The arguments in the OVER clause of the analytic function cannot contain an aggregate. ■ The arguments before the OVER clause of the analytic function cannot contain a cell reference. When expr is itself a model expression, it is referred to as a nested cell reference. The following restrictions apply to nested cell references: ■ Only one level of nesting is allowed. ■ A nested cell reference must be a single-cell reference. ■ When AUTOMATIC ORDER is specified in the model_rules_clause, a nested cell reference can be used on the left-hand side of a model rule only if the measure used in the nested cell reference is never updated for any cell in the spreadsheet clause. See Also: "The MODEL clause: Examples" on page 19-35 for an example of using an analytic function on the right-hand side of a model rule measure_column [ condition expr , ] aggregate_function [ condition expr , single_column_for_loop , multi_column_for_loop ] analytic_function
- 413. Type Constructor Expressions Expressions 6-13 The model expressions shown below are based on the model_clause of the following SELECT statement: SELECT country,prod,year,s FROM sales_view_ref MODEL PARTITION BY (country) DIMENSION BY (prod, year) MEASURES (sale s) IGNORE NAV UNIQUE DIMENSION RULES UPSERT SEQUENTIAL ORDER ( s[prod='Mouse Pad', year=2000] = s['Mouse Pad', 1998] + s['Mouse Pad', 1999], s['Standard Mouse', 2001] = s['Standard Mouse', 2000] ) ORDER BY country, prod, year; The following model expression represents a single cell reference using symbolic notation. It represents the sales of the Mouse Pad for the year 2000. s[prod='Mouse Pad',year=2000] The following model expression represents a multiple cell reference using positional notation, using the CV function. It represents the sales of the current value of the dimension column prod for the year 2001. s[CV(prod), 2001] The following model expression represents an aggregate function. It represents the sum of sales of the Mouse Pad for the years between the current value of the dimension column year less two and the current value of the dimension column year less one. SUM(s)['Mouse Pad',year BETWEEN CV()-2 AND CV()-1] Type Constructor Expressions A type constructor expression specifies a call to a constructor method. The argument to the type constructor is any expression. Type constructors can be invoked anywhere functions are invoked. type_constructor_expression::= The NEW keyword applies to constructors for object types but not for collection types. It instructs Oracle to construct a new object by invoking an appropriate constructor. The use of the NEW keyword is optional, but it is good practice to specify it. If type_name is an object type, then the expressions must be an ordered list, where the first argument is a value whose type matches the first attribute of the object type, the second argument is a value whose type matches the second attribute of the object See Also: CV on page 5-49 and model_clause on page 19-23 NEW schema . type_name ( expr , )
- 414. Type Constructor Expressions 6-14 Oracle Database SQL Reference type, and so on. The total number of arguments to the constructor must match the total number of attributes of the object type. If type_name is a varray or nested table type, then the expression list can contain zero or more arguments. Zero arguments implies construction of an empty collection. Otherwise, each argument corresponds to an element value whose type is the element type of the collection type. Restriction on Type Constructor Invocation In an invocation of a type constructor method, the number of parameters (expr) specified cannot exceed 999, even if the object type has more than 999 attributes. This limitation applies only when the constructor is called from SQL. For calls from PL/SQL, the PL/SQL limitations apply. Expression Example This example uses the cust_address_typ type in the sample oe schema to show the use of an expression in the call to a constructor method (the PL/SQL is shown in italics): CREATE TYPE address_book_t AS TABLE OF cust_address_typ; DECLARE myaddr cust_address_typ := cust_address_typ( '500 Oracle Parkway', 94065, 'Redwood Shores', 'CA','USA'); alladdr address_book_t := address_book_t(); BEGIN INSERT INTO customers VALUES ( 666999, 'Joe', 'Smith', myaddr, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL); END; / Subquery Example This example uses the warehouse_typ type in the sample schema oe to illustrate the use of a subquery in the call to the constructor method. CREATE TABLE warehouse_tab OF warehouse_typ; INSERT INTO warehouse_tab VALUES (warehouse_typ(101, 'new_wh', 201)); CREATE TYPE facility_typ AS OBJECT ( facility_id NUMBER, warehouse_ref REF warehouse_typ); CREATE TABLE buildings (b_id NUMBER, building facility_typ); INSERT INTO buildings VALUES (10, facility_typ(102, (SELECT REF(w) FROM warehouse_tab w WHERE warehouse_name = 'new_wh'))); SELECT b.b_id, b.building.facility_id "FAC_ID", DEREF(b.building.warehouse_ref) "WH" FROM buildings b; B_ID FAC_ID WH(WAREHOUSE_ID, WAREHOUSE_NAME, LOCATION_ID) ---------- ---------- --------------------------------------------- 10 102 WAREHOUSE_TYP(101, 'new_wh', 201) See Also: Oracle Database Application Developer's Guide - Object-Relational Features for additional information on constructor methods and Oracle Database PL/SQL User's Guide and Reference for information on PL/SQL limitations on calls to type constructors
- 415. Expression Lists Expressions 6-15 Variable Expressions A variable expression specifies a host variable with an optional indicator variable. This form of expression can appear only in embedded SQL statements or SQL statements processed in an Oracle Call Interface (OCI) program. variable_expression::= Some valid variable expressions are: :employee_name INDICATOR :employee_name_indicator_var :department_location Expression Lists An expression list is a combination of other expressions. expression_list::= Expression lists can appear in comparison and membership conditions and in GROUP BY clauses of queries and subqueries. Comparison and membership conditions appear in the conditions of WHERE clauses. They can contain either one or more comma-delimited expressions or one or more sets of expressions where each set contains one or more comma-delimited expressions. In the latter case (multiple sets of expressions): ■ Each set is bounded by parentheses ■ Each set must contain the same number of expressions ■ The number of expressions in each set must match the number of expressions before the operator in the comparison condition or before the IN keyword in the membership condition. A comma-delimited list of expressions can contain no more than 1000 expressions. A comma-delimited list of sets of expressions can contain any number of sets, but each set can contain no more than 1000 expressions. The following are some valid expression lists in conditions: (10, 20, 40) ('SCOTT', 'BLAKE', 'TAYLOR') ( ('Guy', 'Himuro', 'GHIMURO'),('Karen', 'Colmenares', 'KCOLMENA') ) In the third example, the number of expressions in each set must equal the number of expressions in the first part of the condition. For example: SELECT * FROM employees : host_variable INDICATOR : indicator_variable expr , ( expr , )
- 416. Expression Lists 6-16 Oracle Database SQL Reference WHERE (first_name, last_name, email) IN (('Guy', 'Himuro', 'GHIMURO'),('Karen', 'Colmenares', 'KCOLMENA')) In a simple GROUP BY clause, you can use either the upper or lower form of expression list: SELECT department_id, MIN(salary), MAX(salary) FROM employees GROUP BY department_id, salary; SELECT department_id, MIN(salary), MAX(salary) FROM employees GROUP BY (department_id, salary); In ROLLUP, CUBE, and GROUPING SETS clauses of GROUP BY clauses, you can combine individual expressions with sets of expressions in the same expression list. The following example shows several valid grouping sets expression lists in one SQL statement: SELECT prod_category, prod_subcategory, country_id, cust_city, count(*) FROM products, sales, customers WHERE sales.prod_id = products.prod_id AND sales.cust_id=customers.cust_id AND sales.time_id = '01-oct-00' AND customers.cust_year_of_birth BETWEEN 1960 and 1970 GROUP BY GROUPING SETS ( (prod_category, prod_subcategory, country_id, cust_city), (prod_category, prod_subcategory, country_id), (prod_category, prod_subcategory), country_id ); See Also: "Comparison Conditions" on page 7-4 and IN Condition conditions on page 7-21 See Also: SELECT on page 19-4
- 417. Conditions 7-1 7 Conditions A condition specifies a combination of one or more expressions and logical (Boolean) operators and returns a value of TRUE, FALSE, or UNKNOWN. This chapter contains the following sections: ■ About SQL Conditions ■ Comparison Conditions ■ Floating-Point Conditions ■ Logical Conditions ■ Model Conditions ■ Multiset Conditions ■ Pattern-matching Conditions ■ Range Conditions ■ Null Conditions ■ XML Conditions ■ Compound Conditions ■ EXISTS Condition ■ IN Condition ■ IS OF type Condition About SQL Conditions Conditions can have several forms, as shown in the following syntax.
- 418. About SQL Conditions 7-2 Oracle Database SQL Reference condition::= If you have installed Oracle Text, then you can create conditions with the built-in operators that are part of that product, including CONTAINS, CATSEARCH, and MATCHES. For more information on these Oracle Text elements, please refer to Oracle Text Reference. If you are using Oracle Expression Filter, then you can create conditions with the built-in EVALUATE operator that is part of that product. For more information, please refer to Oracle Database Application Developer's Guide - Rules Manager and Expression Filter. The sections that follow describe the various forms of conditions. You must use appropriate condition syntax whenever condition appears in SQL statements. You can use a condition in the WHERE clause of these statements: ■ DELETE ■ SELECT ■ UPDATE You can use a condition in any of these clauses of the SELECT statement: ■ WHERE ■ START WITH ■ CONNECT BY ■ HAVING comparison_condition floating_point_condition logical_condition model_condition multiset_condition pattern_matching_condition range_condition null_condition XML_condition compound_condition exists_condition in_condition is_of_type_condition
- 419. About SQL Conditions Conditions 7-3 A condition could be said to be of a logical datatype, although Oracle Database does not formally support such a datatype. The following simple condition always evaluates to TRUE: 1 = 1 The following more complex condition adds the salary value to the commission_ pct value (substituting the value 0 for null) and determines whether the sum is greater than the number constant 25000: NVL(salary, 0) + NVL(salary + (salary*commission_pct, 0) > 25000) Logical conditions can combine multiple conditions into a single condition. For example, you can use the AND condition to combine two conditions: (1 = 1) AND (5 < 7) Here are some valid conditions: name = 'SMITH' employees.department_id = departments.department_id hire_date > '01-JAN-88' job_id IN ('SA_MAN', 'SA_REP') salary BETWEEN 5000 AND 10000 commission_pct IS NULL AND salary = 2100 Condition Precedence Precedence is the order in which Oracle Database evaluates different conditions in the same expression. When evaluating an expression containing multiple conditions, Oracle evaluates conditions with higher precedence before evaluating those with lower precedence. Oracle evaluates conditions with equal precedence from left to right within an expression. Table 7–1 lists the levels of precedence among SQL condition from high to low. Conditions listed on the same line have the same precedence. As the table indicates, Oracle evaluates operators before conditions. Note: The combined values of the NLS_COMP and NLS_SORT settings determine the rules by which characters are sorted and compared. If NLS_COMP is set to LINGUISTIC for your database, then all entities in this chapter will be interpreted according to the rules specified by the NLS_SORT parameter. If NLS_COMP is not set to LINGUISTIC, then the functions are interpreted without regard to the NLS_SORT setting. NLS_SORT can be explicitly set. If it is not set explicitly, it is derived from NLS_LANGUAGE. Please refer to Oracle Database Globalization Support Guide for more information on these settings. See Also: The description of each statement in Chapter 10 through Chapter 19 for the restrictions on the conditions in that statement Table 7–1 SQL Condition Precedence Type of Condition Purpose SQL operators are evaluated before SQL conditions See "Operator Precedence" on page 4-2
- 420. Comparison Conditions 7-4 Oracle Database SQL Reference Comparison Conditions Comparison conditions compare one expression with another. The result of such a comparison can be TRUE, FALSE, or NULL. Large objects (LOBs) are not supported in comparison conditions. However, you can use PL/SQL programs for comparisons on CLOB data. When comparing numeric expressions, Oracle uses numeric precedence to determine whether the condition compares NUMBER, BINARY_FLOAT, or BINARY_DOUBLE values. Please refer to "Numeric Precedence" on page 2-13 for information on numeric precedence. Two objects of nonscalar type are comparable if they are of the same named type and there is a one-to-one correspondence between their elements. In addition, nested tables of user-defined object types, even if their elements are comparable, must have MAP methods defined on them to be used in equality or IN conditions. Table 7–2 lists comparison conditions. =, !=, <, >, <=, >=, comparison IS [NOT] NULL, LIKE, [NOT] BETWEEN, [NOT] IN, EXISTS, IS OF type comparison NOT exponentiation, logical negation AND conjunction OR disjunction See Also: ■ map_order_func_declaration on page 17-24 for more information on MAP methods ■ Oracle Database PL/SQL User's Guide and Reference for the requirements for comparing user-defined object types in PL/SQL Table 7–2 Comparison Conditions Type of Condition Purpose Example = Equality test. SELECT * FROM employees WHERE salary = 2500; != ^= < > ¬= Inequality test. Some forms of the inequality condition may be unavailable on some platforms. SELECT * FROM employees WHERE salary != 2500; > < Greater-than and less-than tests. SELECT * FROM employees WHERE salary > 2500; SELECT * FROM employees WHERE salary < 2500; Table 7–1 (Cont.) SQL Condition Precedence Type of Condition Purpose
- 421. Comparison Conditions Conditions 7-5 Simple Comparison Conditions A simple comparison condition specifies a comparison with expressions or subquery results. simple_comparison_condition::= expression_list::= >= <= Greater-than-or-equal-to and less-than-or-equal-to tests. SELECT * FROM employees WHERE salary >= 2500; SELECT * FROM employees WHERE salary <= 2500; ANY SOME Compares a value to each value in a list or returned by a query. Must be preceded by =, !=, >, <, <=, >=. Can be followed by any expression or subquery that returns one or more values. Evaluates to FALSE if the query returns no rows. SELECT * FROM employees WHERE salary = ANY (SELECT salary FROM employees WHERE department_id = 30); ALL Compares a value to every value in a list or returned by a query. Must be preceded by =, !=, >, <, <=, >=. Can be followed by any expression or subquery that returns one or more values. Evaluates to TRUE if the query returns no rows. SELECT * FROM employees WHERE salary >= ALL ( 1400, 3000); Table 7–2 (Cont.) Comparison Conditions Type of Condition Purpose Example expr = != ^= <> > < >= <= expr ( expr , ) = != ^= <> ( subquery ) expr , ( expr , )
- 422. Comparison Conditions 7-6 Oracle Database SQL Reference If you use the lower form of this condition (with multiple expressions to the left of the operator), then you must use the lower form of the expression_list, and the values returned by the subquery must match in number and datatype the expressions in expression_list. Group Comparison Conditions A group comparison condition specifies a comparison with any or all members in a list or subquery. group_comparison_condition::= expression_list::= If you use the upper form of this condition (with a single expression to the left of the operator), then you must use the upper form of expression_list. If you use the lower form of this condition (with multiple expressions to the left of the operator), then you must use the lower form of expression_list, and the expressions in each expression_list must match in number and datatype the expressions to the left of the operator. See Also: "Expression Lists" on page 6-15 for more information about combining expressions and SELECT on page 19-4 for information about subqueries See Also: ■ "Expression Lists" on page 6-15 ■ SELECT on page 19-4 expr = != ^= <> > < >= <= ANY SOME ALL ( expression_list subquery ) ( expr , ) = != ^= <> ANY SOME ALL ( expression_list ’ subquery ) expr , ( expr , )
- 423. Logical Conditions Conditions 7-7 Floating-Point Conditions The floating-point conditions let you determine whether an expression is infinite or is the undefined result of an operation (that is, is not a number or NaN). floating_point_conditions::= In both forms of floating-point condition, expr must resolve to a numeric datatype or to any datatype that can be implicitly converted to a numeric datatype. Table 7–3 describes the floating-point conditions. Logical Conditions A logical condition combines the results of two component conditions to produce a single result based on them or to invert the result of a single condition. Table 7–4 lists logical conditions. Table 7–3 Floating-Point Conditions Type of Condition Operation Example IS [NOT] NAN Returns TRUE if expr is the special value NaN when NOT is not specified. Returns TRUE if expr is not the special value NaN when NOT is specified. SELECT COUNT(*) FROM employees WHERE commission_pct IS NOT NAN; IS [NOT] INFINITE Returns TRUE if expr is the special value +INF or -INF when NOT is not specified. Returns TRUE if expr is neither +INF nor -INF when NOT is specified. SELECT last_name FROM employees WHERE salary IS NOT INFINITE; See Also: ■ "Floating-Point Numbers" on page 2-11 for more information on the Oracle implementation of floating-point numbers ■ "Implicit Data Conversion" on page 2-41 for more information on how Oracle converts floating-point datatypes expr IS NOT NAN INFINITE
- 424. Logical Conditions 7-8 Oracle Database SQL Reference Table 7–5 shows the result of applying the NOT condition to an expression. Table 7–6 shows the results of combining the AND condition to two expressions. For example, in the WHERE clause of the following SELECT statement, the AND logical condition is used to ensure that only those hired before 1989 and earning more than $2500 a month are returned: SELECT * FROM employees WHERE hire_date < TO_DATE('01-JAN-1989', 'DD-MON-YYYY') AND salary > 2500; Table 7–7 shows the results of applying OR to two expressions. Table 7–4 Logical Conditions Type of Condition Operation Examples NOT Returns TRUE if the following condition is FALSE. Returns FALSE if it is TRUE. If it is UNKNOWN, then it remains UNKNOWN. SELECT * FROM employees WHERE NOT (job_id IS NULL); SELECT * FROM employees WHERE NOT (salary BETWEEN 1000 AND 2000); AND Returns TRUE if both component conditions are TRUE. Returns FALSE if either is FALSE. Otherwise returns UNKNOWN. SELECT * FROM employees WHERE job_id = 'PU_CLERK' AND department_id = 30; OR Returns TRUE if either component condition is TRUE. Returns FALSE if both are FALSE. Otherwise returns UNKNOWN. SELECT * FROM employees WHERE job_id = 'PU_CLERK' OR department_id = 10; Table 7–5 NOT Truth Table -- TRUE FALSE UNKNOWN NOT FALSE TRUE UNKNOWN Table 7–6 AND Truth Table AND TRUE FALSE UNKNOWN TRUE TRUE FALSE UNKNOWN FALSE FALSE FALSE FALSE UNKNOWN UNKNOWN FALSE UNKNOWN Table 7–7 OR Truth Table OR TRUE FALSE UNKNOWN TRUE TRUE TRUE TRUE FALSE TRUE FALSE UNKNOWN UNKNOWN TRUE UNKNOWN UNKNOWN
- 425. Model Conditions Conditions 7-9 For example, the following query returns employees who have a 40% commission rate or a salary greater than $20,000: SELECT employee_id FROM employees WHERE commission_pct = .4 OR salary > 20000; Model Conditions Model conditions can be used only in the MODEL clause of a SELECT statement. IS ANY Condition The IS ANY condition can be used only in the model_clause of a SELECT statement. Use this condition to qualify all values of a dimension column, including NULL. is_any_condition::= The condition always returns a Boolean value of TRUE in order to qualify all values of the column. Example The following example sets sales for each product for year 2000 to 0: SELECT country, prod, year, s FROM sales_view_ref MODEL PARTITION BY (country) DIMENSION BY (prod, year) MEASURES (sale s) IGNORE NAV UNIQUE DIMENSION RULES UPSERT SEQUENTIAL ORDER ( s[ANY, 2000] = 0 ) ORDER BY country, prod, year; COUNTRY PROD YEAR S ---------- ----------------------------------- -------- --------- France Mouse Pad 1998 2509.42 France Mouse Pad 1999 3678.69 France Mouse Pad 2000 0 France Mouse Pad 2001 3269.09 France Standard Mouse 1998 2390.83 France Standard Mouse 1999 2280.45 France Standard Mouse 2000 0 France Standard Mouse 2001 2164.54 Germany Mouse Pad 1998 5827.87 Germany Mouse Pad 1999 8346.44 Germany Mouse Pad 2000 0 Germany Mouse Pad 2001 9535.08 Germany Standard Mouse 1998 7116.11 See Also: model_clause on page 19-23 and "Model Expressions" on page 6-11 for information dimension_column IS ANY
- 426. Model Conditions 7-10 Oracle Database SQL Reference Germany Standard Mouse 1999 6263.14 Germany Standard Mouse 2000 0 Germany Standard Mouse 2001 6456.13 16 rows selected. The preceding example requires the view sales_view_ref. Please refer to "The MODEL clause: Examples" on page 19-35 to create this view. IS PRESENT Condition is_present_condition::= The IS PRESENT condition can be used only in the model_clause of a SELECT statement. Use this condition to test whether the cell referenced is present prior to the execution of the model_clause. The condition returns TRUE if the cell exists prior to the execution of the model_ clause and FALSE if it does not. Example In the following example, if sales of the Mouse Pad for year 1999 exist, then sales of the Mouse Pad for year 2000 is set to sales of the Mouse Pad for year 1999. Otherwise, sales of the Mouse Pad for year 2000 is set to 0. SELECT country, prod, year, s FROM sales_view_ref MODEL PARTITION BY (country) DIMENSION BY (prod, year) MEASURES (sale s) IGNORE NAV UNIQUE DIMENSION RULES UPSERT SEQUENTIAL ORDER ( s['Mouse Pad', 2000] = CASE WHEN s['Mouse Pad', 1999] IS PRESENT THEN s['Mouse Pad', 1999] ELSE 0 END ) ORDER BY country, prod, year; COUNTRY PROD YEAR S ---------- ----------------------------------- -------- --------- France Mouse Pad 1998 2509.42 France Mouse Pad 1999 3678.69 France Mouse Pad 2000 3678.69 France Mouse Pad 2001 3269.09 France Standard Mouse 1998 2390.83 France Standard Mouse 1999 2280.45 France Standard Mouse 2000 1274.31 France Standard Mouse 2001 2164.54 See Also: model_clause on page 19-23 and "Model Expressions" on page 6-11 for information cell_reference IS PRESENT
- 427. Multiset Conditions Conditions 7-11 Germany Mouse Pad 1998 5827.87 Germany Mouse Pad 1999 8346.44 Germany Mouse Pad 2000 8346.44 Germany Mouse Pad 2001 9535.08 Germany Standard Mouse 1998 7116.11 Germany Standard Mouse 1999 6263.14 Germany Standard Mouse 2000 2637.31 Germany Standard Mouse 2001 6456.13 16 rows selected. The preceding example requires the view sales_view_ref. Please refer to "The MODEL clause: Examples" on page 19-35 to create this view. Multiset Conditions Multiset conditions test various aspects of nested tables. IS A SET Condition Use IS A SET conditions to test whether a specified nested table is composed of unique elements. The condition returns NULL if the nested table is NULL. Otherwise, it returns TRUE if the nested table is a set, even if it is a nested table of length zero, and FALSE otherwise. is_a_set_conditions::= Example The following example selects from the table customers_demo those rows in which the cust_address_ntab nested table column contains unique elements: SELECT customer_id, cust_address_ntab FROM customers_demo WHERE cust_address_ntab IS A SET; CUSTOMER_ID CUST_ADDRESS_NTAB(STREET_ADDRESS, POSTAL_CODE, CITY, STATE_PROVINCE, COUNTRY_ID) ---------------------------------------------------------------------------------------------- 101 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('514 W Superior St', '46901', 'Kokomo', 'IN', 'US')) 102 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('2515 Bloyd Ave', '46218', 'Indianapolis', 'IN', 'US')) 103 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('8768 N State Rd 37', '47404', 'Bloomington', 'IN', 'US')) 104 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('6445 Bay Harbor Ln', '46254', 'Indianapolis', 'IN', 'US')) 105 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('4019 W 3Rd St', '47404', 'Bloomington', 'IN', 'US')) The preceding example requires the table customers_demo and a nested table column containing data. Please refer to "Multiset Operators" on page 4-5 to create this table and nested table column. IS EMPTY Condition Use the IS [NOT] EMPTY conditions to test whether a specified nested table is empty. A nested table that consists of a single value, a NULL, is not considered an empty nested table. nested_table IS NOT A SET
- 428. Multiset Conditions 7-12 Oracle Database SQL Reference is_empty_conditions::= The condition returns a Boolean value: TRUE for an IS EMPTY condition if the collection is empty, and TRUE for an IS NOT EMPTY condition if the collection is not empty. If you specify NULL for the nested table or varray, the result is NULL. Example The following example selects from the sample table pm.print_media those rows in which the ad_textdocs_ntab nested table column is not empty: SELECT product_id, TO_CHAR(ad_finaltext) FROM print_media WHERE ad_textdocs_ntab IS NOT EMPTY; MEMBER Condition member_condition::= A member_condition is a membership condition that tests whether an element is a member of a nested table. The return value is TRUE if expr is equal to a member of the specified nested table or varray. The return value is NULL if expr is null or if the nested table is empty. ■ expr must be of the same type as the element type of the nested table. ■ The OF keyword is optional and does not change the behavior of the condition. ■ The NOT keyword reverses the Boolean output: Oracle returns FALSE if expr is a member of the specified nested table. ■ The element types of the nested table must be comparable. Please refer to "Comparison Conditions" on page 7-4 for information on the comparability of nonscalar types. Example The following example selects from the table customers_demo those rows in which the cust_address_ntab nested table column contains the values specified in the WHERE clause: SELECT customer_id, cust_address_ntab FROM customers_demo WHERE cust_address_typ('8768 N State Rd 37', 47404, 'Bloomington', 'IN', 'US') MEMBER OF cust_address_ntab; CUSTOMER_ID CUST_ADDRESS_NTAB(STREET_ADDRESS, POSTAL_CODE, CITY, STATE_PROVINCE, COUNTRY_ID) ------------ --------------------------------------------------------------------------------- 103 CUST_ADDRESS_TAB_TYP(CUST_ADDRESS_TYP('8768 N State Rd 37', '47404', 'Bloomington', 'IN', 'US')) The preceding example requires the table customers_demo and a nested table column containing data. Please refer to "Multiset Operators" on page 4-5 to create this table and nested table column. nested_table IS NOT EMPTY expr NOT MEMBER OF nested_table
- 429. Multiset Conditions Conditions 7-13 SUBMULTISET Condition The SUBMULTISET condition tests whether a specified nested table is a submultiset of another specified nested table. The operator returns a Boolean value. TRUE is returned when nested_table1 is a submultiset of nested_table2. nested_table1 is a submultiset of nested_ table2 when one of the following conditions occur: ■ nested_table1 is not null and contains no rows. TRUE is returned even if nested_table2 is null since an empty multiset is a submultiset of any non-null replacement for nested_table2. ■ nested_table1 and nested_table2 are not null, nested_table1 does not contain a null element, and there is a one-to-one mapping of each element in nested_table1 to an equal element in nested_table2. NULL is returned when one of the following conditions occurs: ■ nested_table1 is null. ■ nested_table2 is null, and nested_table1 is not null and not empty. ■ nested_table1 is a submultiset of nested_table2 after modifying each null element of nested_table1 and nested_table2 to some non-null value, enabling a one-to-one mapping of each element in nested_table1 to an equal element in nested_table2. If none of the above conditions occur, FALSE is returned. submultiset_conditions::= ■ The OF keyword is optional and does not change the behavior of the operator. ■ The NOT keyword reverses the Boolean output: Oracle returns FALSE if nested_ table1 is a subset of nested_table2. ■ The element types of the nested table must be comparable. Please refer to "Comparison Conditions" on page 7-4 for information on the comparability of nonscalar types. Example The following example selects from the customers_demo table those rows in which the cust_address_ntab nested table is a submultiset of the cust_address2_ntab nested table: SELECT customer_id, cust_address_ntab FROM customers_demo WHERE cust_address_ntab SUBMULTISET OF cust_address2_ntab; no rows selected The preceding example requires the table customers_demo and two nested table columns containing data. Please refer to "Multiset Operators" on page 4-5 to create this table and nested table columns. nested_table1 NOT SUBMULTISET OF nested_table2
- 430. Pattern-matching Conditions 7-14 Oracle Database SQL Reference Pattern-matching Conditions The pattern-matching conditions compare character data. LIKE Condition The LIKE conditions specify a test involving pattern matching. Whereas the equality operator (=) exactly matches one character value to another, the LIKE conditions match a portion of one character value to another by searching the first value for the pattern specified by the second. LIKE calculates strings using characters as defined by the input character set. LIKEC uses Unicode complete characters. LIKE2 uses UCS2 code points. LIKE4 uses UCS4 code points. like_condition::= In this syntax: ■ char1 is a character expression, such as a character column, called the search value. ■ char2 is a character expression, usually a literal, called the pattern. ■ esc_char is a character expression, usually a literal, called the escape character. The LIKE condition is the best choice in almost all situations. Use the following guidelines to determine whether any of the variations would be helpful in your environment: ■ Use LIKE2 to process strings using UCS-2 semantics. LIKE2 treats a Unicode supplementary character as two characters. ■ Use LIKE4 to process strings using UCS-4 semantics. LIKE4 treats a Unicode supplementary character as one character. ■ Use LIKEC to process strings using Unicode complete character semantics. LIKEC treats a composite character as one character. If esc_char is not specified, then there is no default escape character. If any of char1, char2, or esc_char is null, then the result is unknown. Otherwise, the escape character, if specified, must be a character string of length 1. All of the character expressions (char1, char2, and esc_char) can be of any of the datatypes CHAR, VARCHAR2, NCHAR, or NVARCHAR2. If they differ, then Oracle converts all of them to the datatype of char1. The pattern can contain special pattern-matching characters: ■ An underscore (_) in the pattern matches exactly one character (as opposed to one byte in a multibyte character set) in the value. ■ A percent sign (%) in the pattern can match zero or more characters (as opposed to bytes in a multibyte character set) in the value. The pattern '%' cannot match a null. char1 NOT LIKE LIKEC LIKE2 LIKE4 char2 ESCAPE esc_char
- 431. Pattern-matching Conditions Conditions 7-15 You can include the actual characters % or _ in the pattern by using the ESCAPE clause, which identifies the escape character. If the escape character precedes the character % or _ in the pattern, then Oracle interprets this character literally in the pattern rather than as a special pattern-matching character. You can also search for the escape character itself by repeating it. For example, if @ is the escape character, then you can use @@ to search for @. Table 7–8 describes the LIKE conditions. To process the LIKE conditions, Oracle divides the pattern into subpatterns consisting of one or two characters each. The two-character subpatterns begin with the escape character and the other character is %, or _, or the escape character. Let P1, P2, ..., Pn be these subpatterns. The like condition is true if there is a way to partition the search value into substrings S1, S2, ..., Sn so that for all i between 1 and n: ■ If Pi is _, then Si is a single character. ■ If Pi is %, then Si is any string. ■ If Pi is two characters beginning with an escape character, then Si is the second character of Pi. ■ Otherwise, Pi = Si. With the LIKE conditions, you can compare a value to a pattern rather than to a constant. The pattern must appear after the LIKE keyword. For example, you can issue the following query to find the salaries of all employees with names beginning with R: SELECT salary FROM employees WHERE last_name LIKE 'R%'; The following query uses the = operator, rather than the LIKE condition, to find the salaries of all employees with the name 'R%': SELECT salary FROM employees WHERE last_name = 'R%'; The following query finds the salaries of all employees with the name 'SM%'. Oracle interprets 'SM%' as a text literal, rather than as a pattern, because it precedes the LIKE keyword: SELECT salary FROM employees WHERE 'SM%' LIKE last_name; Table 7–8 LIKE Conditions Type of Condition Operation Example x [NOT] LIKE y [ESCAPE 'z'] TRUE if x does [not] match the pattern y. Within y, the character % matches any string of zero or more characters except null. The character _ matches any single character. Any character can follow ESCAPE except percent (%) and underbar (_). A wildcard character is treated as a literal if preceded by the escape character. SELECT last_name FROM employees WHERE last_name LIKE '%A_B%' ESCAPE '';
- 432. Pattern-matching Conditions 7-16 Oracle Database SQL Reference Case Sensitivity Case is significant in all conditions comparing character expressions that use the LIKE condition and the equality (=) operators. You can perform case or accent insensitive LIKE searches by setting the NLS_SORT and the NLS_COMP session parameters. Pattern Matching on Indexed Columns When you use LIKE to search an indexed column for a pattern, Oracle can use the index to improve performance of a query if the leading character in the pattern is not % or _. In this case, Oracle can scan the index by this leading character. If the first character in the pattern is % or _, then the index cannot improve performance because Oracle cannot scan the index. LIKE Condition: General Examples This condition is true for all last_name values beginning with Ma: last_name LIKE 'Ma%' All of these last_name values make the condition true: Mallin, Markle, Marlow, Marvins, Marvis, Matos Case is significant, so last_name values beginning with MA, ma, and mA make the condition false. Consider this condition: last_name LIKE 'SMITH_' This condition is true for these last_name values: SMITHE, SMITHY, SMITHS This condition is false for SMITH because the special underscore character (_) must match exactly one character of the last_name value. ESCAPE Clause Example The following example searches for employees with the pattern A_B in their name: SELECT last_name FROM employees WHERE last_name LIKE '%A_B%' ESCAPE ''; The ESCAPE clause identifies the backslash () as the escape character. In the pattern, the escape character precedes the underscore (_). This causes Oracle to interpret the underscore literally, rather than as a special pattern matching character. Patterns Without % Example If a pattern does not contain the % character, then the condition can be true only if both operands have the same length. Consider the definition of this table and the values inserted into it: CREATE TABLE ducks (f CHAR(6), v VARCHAR2(6)); INSERT INTO ducks VALUES ('DUCK', 'DUCK'); SELECT '*'||f||'*' "char", '*'||v||'*' "varchar" FROM ducks; char varchar See Also: Oracle Database Globalization Support Guide for more information on this case- and accent-insensitive linguistic sorts
- 433. Pattern-matching Conditions Conditions 7-17 -------- -------- *DUCK * *DUCK* Because Oracle blank-pads CHAR values, the value of f is blank-padded to 6 bytes. v is not blank-padded and has length 4. REGEXP_LIKE Condition REGEXP_LIKE is similar to the LIKE condition, except REGEXP_LIKE performs regular expression matching instead of the simple pattern matching performed by LIKE. This condition evaluates strings using characters as defined by the input character set. This condition complies with the POSIX regular expression standard and the Unicode Regular Expression Guidelines. For more information, please refer to Appendix C, "Oracle Regular Expression Support". regexp_like_condition::= ■ source_char is a character expression that serves as the search value. It is commonly a character column and can be of any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. ■ pattern is the regular expression. It is usually a text literal and can be of any of the datatypes CHAR, VARCHAR2, NCHAR, or NVARCHAR2. It can contain up to 512 bytes. If the datatype of pattern is different from the datatype of source_char, Oracle converts pattern to the datatype of source_char. For a listing of the operators you can specify in pattern, please refer to Appendix C, "Oracle Regular Expression Support". ■ match_parameter is a text literal that lets you change the default matching behavior of the function. You can specify one or more of the following values for match_parameter: – 'i' specifies case-insensitive matching. – 'c' specifies case-sensitive matching. – 'n' allows the period (.), which is the match-any-character wildcard character, to match the newline character. If you omit this parameter, the period does not match the newline character. – 'm' treats the source string as multiple lines. Oracle interprets ^ and $ as the start and end, respectively, of any line anywhere in the source string, rather than only at the start or end of the entire source string. If you omit this parameter, Oracle treats the source string as a single line. – 'x' ignores whitespace characters. By default, whitespace characters match themselves. If you specify multiple contradictory values, Oracle uses the last value. For example, if you specify 'ic', then Oracle uses case-sensitive matching. If you specify a character other than those shown above, then Oracle returns an error. If you omit match_parameter, then: – The default case sensitivity is determined by the value of the NLS_SORT parameter. REGEXP_LIKE ( source_char , pattern , match_parameter )
- 434. Range Conditions 7-18 Oracle Database SQL Reference – A period (.) does not match the newline character. – The source string is treated as a single line. Examples The following query returns the first and last names for those employees with a first name of Steven or Stephen (where first_name begins with Ste and ends with en and in between is either v or ph): SELECT first_name, last_name FROM employees WHERE REGEXP_LIKE (first_name, '^Ste(v|ph)en$'); FIRST_NAME LAST_NAME -------------------- ------------------------- Steven King Steven Markle Stephen Stiles The following query returns the last name for those employees with a double vowel in their last name (where last_name contains two adjacent occurrences of either a, e, i, o, or u, regardless of case): SELECT last_name FROM employees WHERE REGEXP_LIKE (last_name, '([aeiou])1', 'i'); LAST_NAME ------------------------- De Haan Greenberg Khoo Gee Greene Lee Bloom Feeney Range Conditions A range condition tests for inclusion in a range. range_conditions::= Table 7–9 describes the range conditions. See Also: ■ "LIKE Condition" on page 7-14 ■ REGEXP_INSTR on page 5-136, REGEXP_REPLACE on page 5-138, and REGEXP_SUBSTR on page 5-140 for functions that provide regular expression support expr NOT BETWEEN expr AND expr
- 435. XML Conditions Conditions 7-19 Null Conditions A NULL condition tests for nulls. This is the only condition that you should use to test for nulls. null_conditions::= Table 7–10 lists the null conditions. XML Conditions XML conditions determines whether a specified XML resource can be found in a specified path. EQUALS_PATH Condition The EQUALS_PATH condition determines whether a resource in the Oracle XML database can be found in the database at a specified path. Use this condition in queries to RESOURCE_VIEW and PATH_VIEW. These public views provide a mechanism for SQL access to data stored in the XML database repository. RESOURCE_VIEW contains one row for each resource in the repository, and PATH_ VIEW contains one row for each unique path in the repository. equals_path_condition::= This condition applies only to the path as specified. It is similar to but more restrictive than UNDER_PATH. The optional correlation_integer argument correlates the EQUALS_PATH condition with its ancillary functions DEPTH and PATH. Table 7–9 Range Conditions Type of Condition Operation Example [NOT] BETWEEN x AND y [Not] greater than or equal to x and less than or equal to y. SELECT * FROM employees WHERE salary BETWEEN 2000 AND 3000; Table 7–10 Null Conditions Type of Condition Operation Example IS [NOT] NULL Tests for nulls. See Also: "Nulls" on page 2-68 SELECT last_name FROM employees WHERE commission_pct IS NULL; expr IS NOT NULL EQUALS_PATH ( column , path_string , correlation_integer )
- 436. XML Conditions 7-20 Oracle Database SQL Reference Example The view RESOURCE_VIEW computes the paths (in the any_path column) that lead to all XML resources (in the res column) in the database repository. The following example queries the RESOURCE_VIEW view to find the paths to the resources in the sample schema oe. The EQUALS_PATH condition causes the query to return only the specified path: SELECT ANY_PATH FROM RESOURCE_VIEW WHERE EQUALS_PATH(res, '/sys/schemas/OE/www.oracle.com')=1; ANY_PATH ----------------------------------------------- /sys/schemas/OE/www.oracle.com Compare this example with that for UNDER_PATH Condition on page 7-20. UNDER_PATH Condition The UNDER_PATH condition determines whether resources specified in a column can be found under a particular path specified by path_string in the Oracle XML database repository. The path information is computed by the RESOURCE_VIEW view, which you query to use this condition. Use this condition in queries to RESOURCE_VIEW and PATH_VIEW. These public views provide a mechanism for SQL access to data stored in the XML database repository. RESOURCE_VIEW contains one row for each resource in the repository, and PATH_ VIEW contains one row for each unique path in the repository. under_path_condition::= The optional levels argument indicates the number of levels down from path_ string Oracle should search. For levels, specify any nonnegative integer. The optional correlation_integer argument correlates the UNDER_PATH condition with its ancillary functions PATH and DEPTH. Example The view RESOURCE_VIEW computes the paths (in the any_path column) that lead to all XML resources (in the res column) in the database repository. The following example queries the RESOURCE_VIEW view to find the paths to the resources in the sample schema oe. The query returns the path of the XML schema that was created in "XMLType Table Examples" on page 16-55: SELECT ANY_PATH FROM RESOURCE_VIEW WHERE UNDER_PATH(res, '/sys/schemas/OE/www.oracle.com')=1; ANY_PATH See Also: UNDER_PATH Condition on page 7-20, DEPTH on page 5-55, and PATH on page 5-112 See Also: The related condition EQUALS_PATH Condition on page 7-19 and the ancillary functions DEPTH on page 5-55 and PATH on page 5-112 UNDER_PATH ( column , levels , path_string , correlation_integer )
- 437. IN Condition Conditions 7-21 ---------------------------------------------- /sys/schemas/OE/www.oracle.com/xwarehouses.xsd Compound Conditions A compound condition specifies a combination of other conditions. compound_conditions::= EXISTS Condition An EXISTS condition tests for existence of rows in a subquery. Table 7–11 shows the EXISTS condition. IN Condition An in_condition is a membership condition. It tests a value for membership in a list of values or subquery in_conditions::= See Also: "Logical Conditions" on page 7-7 for more information about NOT, AND, and OR conditions Table 7–11 EXISTS Condition Type of Condition Operation Example EXISTS TRUE if a subquery returns at least one row. SELECT department_id FROM departments d WHERE EXISTS (SELECT * FROM employees e WHERE d.department_id = e.department_id); ( condition ) NOT condition condition AND OR condition EXISTS ( subquery ) expr NOT IN ( expression_list subquery ) ( expr , ) NOT IN ( expression_list , subquery )
- 438. IN Condition 7-22 Oracle Database SQL Reference expression_list::= If you use the upper form of the in_condition condition (with a single expression to the left of the operator), then you must use the upper form of expression_list. If you use the lower form of this condition (with multiple expressions to the left of the operator), then you must use the lower form of expression_list, and the expressions in each expression_list must match in number and datatype the expressions to the left of the operator. Table 7–12 lists the form of IN condition. If any item in the list following a NOT IN operation evaluates to null, then all rows evaluate to FALSE or UNKNOWN, and no rows are returned. For example, the following statement returns the string 'True' for each row: SELECT 'True' FROM employees WHERE department_id NOT IN (10, 20); However, the following statement returns no rows: SELECT 'True' FROM employees WHERE department_id NOT IN (10, 20, NULL); The preceding example returns no rows because the WHERE clause condition evaluates to: department_id != 10 AND department_id != 20 AND department_id != null See Also: "Expression Lists" on page 6-15 Table 7–12 IN Conditions Type of Condition Operation Example IN Equal-to-any-member-of test. Equivalent to =ANY. SELECT * FROM employees WHERE job_id IN ('PU_CLERK','SH_CLERK'); SELECT * FROM employees WHERE salary IN (SELECT salary FROM employees WHERE department_id =30); NOT IN Equivalent to !=ALL. Evaluates to FALSE if any member of the set is NULL. SELECT * FROM employees WHERE salary NOT IN (SELECT salary FROM employees WHERE department_id = 30); SELECT * FROM employees WHERE job_id NOT IN ('PU_CLERK', 'SH_CLERK'); expr , ( expr , )
- 439. IS OF type Condition Conditions 7-23 Because the third condition compares department_id with a null, it results in an UNKNOWN, so the entire expression results in FALSE (for rows with department_id equal to 10 or 20). This behavior can easily be overlooked, especially when the NOT IN operator references a subquery. Moreover, if a NOT IN condition references a subquery that returns no rows at all, then all rows will be returned, as shown in the following example: SELECT 'True' FROM employees WHERE department_id NOT IN (SELECT 0 FROM DUAL WHERE 1=2); Restriction on LEVEL in WHERE Clauses In a [NOT] IN condition in a WHERE clause, if the right-hand side of the condition is a subquery, you cannot use LEVEL on the left-hand side of the condition. However, you can specify LEVEL in a subquery of the FROM clause to achieve the same result. For example, the following statement is not valid: SELECT employee_id, last_name FROM employees WHERE (employee_id, LEVEL) IN (SELECT employee_id, 2 FROM employees) START WITH employee_id = 2 CONNECT BY PRIOR employee_id = manager_id; But the following statement is valid because it encapsulates the query containing the LEVEL information in the FROM clause: SELECT v.employee_id, v.last_name, v.lev FROM (SELECT employee_id, last_name, LEVEL lev FROM employees v START WITH employee_id = 100 CONNECT BY PRIOR employee_id = manager_id) v WHERE (v.employee_id, v.lev) IN (SELECT employee_id, 2 FROM employees); IS OF type Condition Use the IS OF type condition to test object instances based on their specific type information. is_of_type_conditions::= You must have EXECUTE privilege on all types referenced by type, and all types must belong to the same type family. This condition evaluates to null if expr is null. If expr is not null, then the condition evaluates to true (or false if you specify the NOT keyword) under either of these circumstances: ■ The most specific type of expr is the subtype of one of the types specified in the type list and you have not specified ONLY for the type, or ■ The most specific type of expr is explicitly specified in the type list. The expr frequently takes the form of the VALUE function with a correlation variable. expr IS NOT OF TYPE ( ONLY schema . type , )
- 440. IS OF type Condition 7-24 Oracle Database SQL Reference The following example uses the sample table oe.persons, which is built on a type hierarchy in "Substitutable Table and Column Examples" on page 16-51. The example uses the IS OF type condition to restrict the query to specific subtypes: SELECT * FROM persons p WHERE VALUE(p) IS OF TYPE (employee_t); NAME SSN ---------------------------- Joe 32456 Tim 5678 SELECT * FROM persons p WHERE VALUE(p) IS OF (ONLY part_time_emp_t); NAME SSN ---------------------------- Tim 5678
- 441. Common SQL DDL Clauses 8-1 8 Common SQL DDL Clauses This chapter describes some SQL data definition clauses that appear in multiple SQL statements. This chapter contains these sections: ■ allocate_extent_clause ■ constraint ■ deallocate_unused_clause ■ file_specification ■ logging_clause ■ parallel_clause ■ physical_attributes_clause ■ size_clause ■ storage_clause
- 442. allocate_extent_clause 8-2 Oracle Database SQL Reference allocate_extent_clause Purpose Use the allocate_extent_clause clause to explicitly allocate a new extent for a database object. Explicitly allocating an extent with this clause does not change the values of the NEXT and PCTINCREASE storage parameters, so does not affect the size of the next extent to be allocated implicitly by Oracle Database. Please refer to storage_clause on page 8-46 for information about the NEXT and PCTINCREASE storage parameters. You can allocate an extent in the following SQL statements: ■ ALTER CLUSTER (see ALTER CLUSTER on page 10-5) ■ ALTER INDEX: to allocate an extent to the index, an index partition, or an index subpartition (see ALTER INDEX on page 10-64) ■ ALTER MATERIALIZED VIEW: to allocate an extent to the materialized view, one of its partitions or subpartitions, or the overflow segment of an index-organized materialized view (see ALTER MATERIALIZED VIEW on page 11-2) ■ ALTER MATERIALIZED VIEW LOG (see ALTER MATERIALIZED VIEW LOG on page 11-15) ■ ALTER TABLE: to allocate an extent to the table, a table partition, a table subpartition, the mapping table of an index-organized table, the overflow segment of an index-organized table, or a LOB storage segment (see ALTER TABLE on page 12-2) Syntax allocate_extent_clause::= (size_clause::= on page 8-45) Semantics This section describes the parameters of the allocate_extent_clause. For additional information, refer to the SQL statement in which you set or reset these parameters for a particular database object. You cannot specify the allocate_extent_clause and the deallocate_unused_ clause in the same statement. SIZE Specify the size of the extent in bytes. The value of integer can be 0 through 2147483647. To specify a larger extent size, use an integer within this range with K, M, G, or T to specify the extent size in kilobytes, megabytes, gigabytes, or terabytes. ALLOCATE EXTENT ( SIZE size_clause DATAFILE ’ filename ’ INSTANCE integer )
- 443. allocate_extent_clause Common SQL DDL Clauses 8-3 For a table, index, materialized view, or materialized view log, if you omit SIZE, then Oracle Database determines the size based on the values of the storage parameters of the object. However, for a cluster, Oracle does not evaluate the cluster's storage parameters, so you must specify SIZE if you do not want Oracle to use a default value. DATAFILE 'filename' Specify one of the datafiles in the tablespace of the table, cluster, index, materialized view, or materialized view log to contain the new extent. If you omit DATAFILE, then Oracle chooses the datafile. INSTANCE integer Use this parameter only if you are using Oracle with Real Application Clusters. Specifying INSTANCE integer makes the new extent available to the freelist group associated with the specified instance. If the instance number exceeds the maximum number of freelist groups, then Oracle divides the specified number by the maximum number and uses the remainder to identify the freelist group to be used. An instance is identified by the value of its initialization parameter INSTANCE_NUMBER. If you omit this parameter, then the space is allocated to the table, cluster, index, materialized view, or materialized view log but is not drawn from any particular freelist group. Instead, Oracle uses the master freelist and allocates space as needed. Note: If you are using automatic segment-space management, then the INSTANCE parameter of the allocate_extent_clause may not reserve the newly allocated space for the specified instance, because automatic segment-space management does not maintain rigid affinity between extents and instances. See Also: Oracle Database Oracle Clusterware and Oracle Real Application Clusters Administration and Deployment Guide for more information on setting the INSTANCE parameter of allocate_ extent_clause
- 444. constraint 8-4 Oracle Database SQL Reference constraint Purpose Use a constraint to define an integrity constraint--a rule that restricts the values in a database. Oracle Database lets you create six types of constraints and lets you declare them in two ways. The six types of integrity constraint are described briefly here and more fully in "Semantics" on page 8-8: ■ A NOT NULL constraint prohibits a database value from being null. ■ A unique constraint prohibits multiple rows from having the same value in the same column or combination of columns but allows some values to be null. ■ A primary key constraint combines a NOT NULL constraint and a unique constraint in a single declaration. That is, it prohibits multiple rows from having the same value in the same column or combination of columns and prohibits values from being null. ■ A foreign key constraint requires values in one table to match values in another table. ■ A check constraint requires a value in the database to comply with a specified condition. ■ A REF column by definition references an object in another object type or in a relational table. A REF constraint lets you further describe the relationship between the REF column and the object it references. You can define constraints syntactically in two ways: ■ As part of the definition of an individual column or attribute. This is called inline specification. ■ As part of the table definition. This is called out-of-line specification. NOT NULL constraints must be declared inline. All other constraints can be declared either inline or out of line. Constraint clauses can appear in the following statements: ■ CREATE TABLE (see CREATE TABLE on page 16-6) ■ ALTER TABLE (see ALTER TABLE on page 12-2) ■ CREATE VIEW (see CREATE VIEW on page 17-32) ■ ALTER VIEW (see ALTER VIEW on page 13-25) View Constraints Oracle Database does not enforce view constraints. However, you can enforce constraints on views through constraints on base tables. You can specify only unique, primary key, and foreign key constraints on views, and they are supported only in DISABLE NOVALIDATE mode. You cannot define view constraints on attributes of an object column. See Also: "View Constraints" on page 8-18 for additional information on view constraints and "DISABLE Clause" on page 8-15 for information on DISABLE NOVALIDATE mode
- 445. constraint Common SQL DDL Clauses 8-5 Prerequisites You must have the privileges necessary to issue the statement in which you are defining the constraint. To create a foreign key constraint, in addition, the parent table or view must be in your own schema or you must have the REFERENCES privilege on the columns of the referenced key in the parent table or view. Syntax constraint::= (inline_constraint::= on page 8-5, out_of_line_constraint::= on page 8-5, inline_ref_ constraint::= on page 8-6, out_of_line_ref_constraint::= on page 8-6) inline_constraint::= (references_clause::= on page 8-6) out_of_line_constraint::= (references_clause::= on page 8-6, constraint_state::= on page 8-6) inline_constraint out_of_line_constraint inline_ref_constraint out_of_line_ref_constraint CONSTRAINT constraint_name NOT NULL UNIQUE PRIMARY KEY references_clause CHECK ( condition ) constraint_state CONSTRAINT constraint_name UNIQUE ( column , ) PRIMARY KEY ( column , ) FOREIGN KEY ( column , ) references_clause CHECK ( condition ) constraint_state
- 446. constraint 8-6 Oracle Database SQL Reference inline_ref_constraint::= (references_clause::= on page 8-6, constraint_state::= on page 8-6) out_of_line_ref_constraint::= (references_clause::= on page 8-6, constraint_state::= on page 8-6) references_clause::= constraint_state::= (using_index_clause::= on page 8-7, exceptions_clause::= on page 8-7) SCOPE IS schema . scope_table WITH ROWID CONSTRAINT constraint_name references_clause constraint_state SCOPE FOR ( ref_col ref_attr ) IS schema . scope_table REF ( ref_col ref_attr ) WITH ROWID CONSTRAINT constraint_name FOREIGN KEY ( ref_col ref_attr ) references_clause constraint_state REFERENCES schema . object ( column ) ON DELETE CASCADE SET NULL NOT DEFERRABLE INITIALLY IMMEDIATE DEFERRED ENABLE DISABLE VALIDATE NOVALIDATE RELY NORELY using_index_clause exceptions_clause
- 447. constraint Common SQL DDL Clauses 8-7 using_index_clause::= (create_index::= on page 14-59, index_properties::= on page 8-7) index_properties::= (global_partitioned_index::= on page 14-61, local_partitioned_index::= on page 14-62--part of CREATE INDEX, index_attributes::= on page 8-7, domain_index_clause: not supported in using_index_clause) index_attributes::= (physical_attributes_clause::= on page 14-3, logging_clause::= on page 8-36, 1::= on page 14-61--all part of CREATE INDEX, parallel_clause: not supported in using_ index_clause) exceptions_clause::= USING INDEX schema . index ( create_index_statement ) index_properties global_partitioned_index local_partitioned_index index_attributes domain_index_clause physical_attributes_clause logging_clause ONLINE COMPUTE STATISTICS TABLESPACE tablespace DEFAULT key_compression SORT NOSORT REVERSE parallel_clause EXCEPTIONS INTO schema . table
- 448. constraint 8-8 Oracle Database SQL Reference Semantics This section describes the semantics of constraint. For additional information, refer to the SQL statement in which you define or redefine a constraint for a table or view. Oracle Database does not support constraints on columns or attributes whose type is a user-defined object, nested table, VARRAY, REF, or LOB, with two exceptions: ■ NOT NULL constraints are supported for a column or attribute whose type is user-defined object, VARRAY, REF, or LOB. ■ NOT NULL, foreign key, and REF constraints are supported on a column of type REF. CONSTRAINT constraint_name Specify a name for the constraint. If you omit this identifier, then Oracle Database generates a name with the form SYS_Cn. Oracle stores the name and the definition of the integrity constraint in the USER_, ALL_, and DBA_ CONSTRAINTS data dictionary views (in the CONSTRAINT_NAME and SEARCH_ CONDITION columns, respectively). NOT NULL Constraints A NOT NULL constraint prohibits a column from containing nulls. The NULL keyword by itself does not actually define an integrity constraint, but you can specify it to explicitly permit a column to contain nulls. You must define NOT NULL and NULL using inline specification. If you specify neither NOT NULL nor NULL, then the default is NULL. NOT NULL constraints are the only constraints you can specify inline on XMLType and VARRAY columns. To satisfy a NOT NULL constraint, every row in the table must contain a value for the column. Restrictions on NOT NULL Constraints NOT NULL constraints are subject to the following restrictions: ■ You cannot specify NULL or NOT NULL in a view constraint. ■ You cannot specify NULL or NOT NULL for an attribute of an object. Instead, use a CHECK constraint with the IS [NOT] NULL condition. Unique Constraints A unique constraint designates a column as a unique key. A composite unique key designates a combination of columns as the unique key. When you define a unique constraint inline, you need only the UNIQUE keyword. When you define a unique See Also: Oracle Database Reference for information on the data dictionary views Note: Oracle Database does not index table rows in which all key columns are null except in the case of bitmap indexes. Therefore, if you want an index on all rows of a table, then you must either specify NOT NULL constraints for at least one of the index key columns or create a bitmap index. See Also: "Attribute-Level Constraints Example" on page 8-24 and "NOT NULL Example" on page 8-20
- 449. constraint Common SQL DDL Clauses 8-9 constraint out of line, you must also specify one or more columns. You must define a composite unique key out of line. To satisfy a unique constraint, no two rows in the table can have the same value for the unique key. However, the unique key made up of a single column can contain nulls. To satisfy a composite unique key, no two rows in the table or view can have the same combination of values in the key columns. Any row that contains nulls in all key columns automatically satisfies the constraint. However, two rows that contain nulls for one or more key columns and the same combination of values for the other key columns violate the constraint. When you specify a unique constraint on one or more columns, Oracle implicitly creates an index on the unique key. If you are defining uniqueness for purposes of query performance, then Oracle recommends that you instead create the unique index explicitly using a CREATE UNIQUE INDEX statement. You can also use the CREATE UNIQUE INDEX statement to create a unique function-based index that defines a conditional unique constraint. See "Using a Function-based Index to Define Conditional Uniqueness: Example" on page 14-77 for more information. Restrictions on Unique Constraints Unique constraints are subject to the following restrictions: ■ None of the columns in the unique key can be of LOB, LONG, LONG RAW, VARRAY, NESTED TABLE, OBJECT, REF, TIMESTAMP WITH TIME ZONE, or user-defined type. However, the unique key can contain a column of TIMESTAMP WITH LOCAL TIME ZONE. ■ A composite unique key cannot have more than 32 columns. ■ You cannot designate the same column or combination of columns as both a primary key and a unique key. ■ You cannot specify a unique key when creating a subview in an inheritance hierarchy. The unique key can be specified only for the top-level (root) view. Primary Key Constraints A primary key constraint designates a column as the primary key of a table or view. A composite primary key designates a combination of columns as the primary key. When you define a primary key constraint inline, you need only the PRIMARY KEY keywords. When you define a primary key constraint out of line, you must also specify one or more columns. You must define a composite primary key out of line. A primary key constraint combines a NOT NULL and unique constraint in one declaration. Therefore, to satisfy a primary key constraint: ■ No primary key value can appear in more than one row in the table. ■ No column that is part of the primary key can contain a null. Restrictions on Primary Key Constraints Primary constraints are subject to the following restrictions: ■ A table or view can have only one primary key. ■ None of the columns in the primary key can be LOB, LONG, LONG RAW, VARRAY, NESTED TABLE, BFILE, REF, TIMESTAMP WITH TIME ZONE, or user-defined type. See Also: "Unique Key Example" on page 8-19 and Composite Unique Key Example on page 8-19
- 450. constraint 8-10 Oracle Database SQL Reference However, the primary key can contain a column of TIMESTAMP WITH LOCAL TIME ZONE. ■ The size of the primary key cannot exceed approximately one database block. ■ A composite primary key cannot have more than 32 columns. ■ You cannot designate the same column or combination of columns as both a primary key and a unique key. ■ You cannot specify a primary key when creating a subview in an inheritance hierarchy. The primary key can be specified only for the top-level (root) view. Foreign Key Constraints A foreign key constraint (also called a referential integrity constraint) designates a column as the foreign key and establishes a relationship between that foreign key and a specified primary or unique key, called the referenced key. A composite foreign key designates a combination of columns as the foreign key. The table or view containing the foreign key is called the child object, and the table or view containing the referenced key is called the parent object. The foreign key and the referenced key can be in the same table or view. In this case, the parent and child tables are the same. If you identify only the parent table or view and omit the column name, then the foreign key automatically references the primary key of the parent table or view. The corresponding column or columns of the foreign key and the referenced key must match in order and datatype. You can define a foreign key constraint on a single key column either inline or out of line. You must specify a composite foreign key and a foreign key on an attribute out of line. To satisfy a composite foreign key constraint, the composite foreign key must refer to a composite unique key or a composite primary key in the parent table or view, or the value of at least one of the columns of the foreign key must be null. You can designate the same column or combination of columns as both a foreign key and a primary or unique key. You can also designate the same column or combination of columns as both a foreign key and a cluster key. You can define multiple foreign keys in a table or view. Also, a single column can be part of more than one foreign key. Restrictions on Foreign Key Constraints Foreign key constraints are subject to the following restrictions: ■ None of the columns in the foreign key can be of LOB, LONG, LONG RAW, VARRAY, NESTED TABLE, BFILE, REF, TIMESTAMP WITH TIME ZONE, or user-defined type. However, the primary key can contain a column of TIMESTAMP WITH LOCAL TIME ZONE. ■ The referenced unique or primary key constraint on the parent table or view must already be defined. ■ A composite foreign key cannot have more than 32 columns. ■ The child and parent tables must be on the same database. To enable referential integrity constraints across nodes of a distributed database, you must use database triggers. See CREATE TRIGGER on page 16-75. See Also: "Primary Key Example" on page 8-19 and "Composite Primary Key Example" on page 8-20
- 451. constraint Common SQL DDL Clauses 8-11 ■ If either the child or parent object is a view, then the constraint is subject to all restrictions on view constraints. See "View Constraints" on page 8-18. ■ You cannot define a foreign key constraint in a CREATE TABLE statement that contains an AS subquery clause. Instead, you must create the table without the constraint and then add it later with an ALTER TABLE statement. references_clause Foreign key constraints use the references_clause syntax. When you specify a foreign key constraint inline, you need only the references_ clause. When you specify a foreign key constraint out of line, you must also specify the FOREIGN KEY keywords and one or more columns. ON DELETE Clause The ON DELETE clause lets you determine how Oracle Database automatically maintains referential integrity if you remove a referenced primary or unique key value. If you omit this clause, then Oracle does not allow you to delete referenced key values in the parent table that have dependent rows in the child table. ■ Specify CASCADE if you want Oracle to remove dependent foreign key values. ■ Specify SET NULL if you want Oracle to convert dependent foreign key values to NULL. Restriction on ON DELETE You cannot specify this clause for a view constraint. Check Constraints A check constraint lets you specify a condition that each row in the table must satisfy. To satisfy the constraint, each row in the table must make the condition either TRUE or unknown (due to a null). When Oracle evaluates a check constraint condition for a particular row, any column names in the condition refer to the column values in that row. The syntax for inline and out-of-line specification of check constraints is the same. However, inline specification can refer only to the column (or the attributes of the column if it is an object column) currently being defined, whereas out-of-line specification can refer to multiple columns or attributes. Oracle does not verify that conditions of check constraints are not mutually exclusive. Therefore, if you create multiple check constraints for a column, design them carefully so their purposes do not conflict. Do not assume any particular order of evaluation of the conditions. Restrictions on Check Constraints Check constraints are subject to the following restrictions: See Also: ■ Oracle Database Application Developer's Guide - Fundamentals for more information on using constraints ■ "Foreign Key Constraint Example" on page 8-20 and "Composite Foreign Key Constraint Example" on page 8-22 See Also: "ON DELETE Example" on page 8-21 See Also: ■ Chapter 7, "Conditions" for additional information and syntax ■ "Check Constraint Examples" on page 8-22 and "Attribute-Level Constraints Example" on page 8-24
- 452. constraint 8-12 Oracle Database SQL Reference ■ You cannot specify a check constraint for a view. However, you can define the view using the WITH CHECK OPTION clause, which is equivalent to specifying a check constraint for the view. ■ The condition of a check constraint can refer to any column in the table, but it cannot refer to columns of other tables. ■ Conditions of check constraints cannot contain the following constructs: – Subqueries and scalar subquery expressions – Calls to the functions that are not deterministic (CURRENT_DATE, CURRENT_ TIMESTAMP, DBTIMEZONE, LOCALTIMESTAMP, SESSIONTIMEZONE, SYSDATE, SYSTIMESTAMP, UID, USER, and USERENV) – Calls to user-defined functions – Dereferencing of REF columns (for example, using the DEREF function) – Nested table columns or attributes – The pseudocolumns CURRVAL, NEXTVAL, LEVEL, or ROWNUM – Date constants that are not fully specified REF Constraints REF constraints let you describe the relationship between a column of type REF and the object it references. ref_constraint REF constraints use the ref_constraint syntax. You define a REF constraint either inline or out of line. Out-of-line specification requires you to specify the REF column or attribute you are further describing. ■ For ref_column, specify the name of a REF column of an object or relational table. ■ For ref_attribute, specify an embedded REF attribute within an object column of a relational table. Both inline and out-of-line specification let you define a scope constraint, a rowid constraint, or a referential integrity constraint on a REF column. If the scope table or referenced table of the REF column has a primary-key-based object identifier, then the REF column is a user-defined REF column. SCOPE REF Constraints In a table with a REF column, each REF value in the column can conceivably reference a row in a different object table. The SCOPE clause restricts the scope of references to a single table, scope_table. The values in the REF column or attribute point to objects in scope_table, in which object instances of the same type as the REF column are stored. Specify the SCOPE clause to restrict the scope of references in the REF column to a single table. For you to specify this clause, scope_table must be in your own schema or you must have SELECT privileges on scope_table or SELECT ANY TABLE system privileges. You can specify only one scope table for each REF column. See Also: ■ Oracle Database Concepts for more information on REF datatypes ■ "Foreign Key Constraints" on page 8-10, and "REF Constraint Examples" on page 8-24
- 453. constraint Common SQL DDL Clauses 8-13 Restrictions on Scope Constraints Scope constraints are subject to the following restrictions: ■ You cannot add a scope constraint to an existing column unless the table is empty. ■ You cannot specify a scope constraint for the REF elements of a VARRAY column. ■ You must specify this clause if you specify AS subquery and the subquery returns user-defined REF datatypes. ■ You cannot subsequently drop a scope constraint from a REF column. Rowid REF Constraints Specify WITH ROWID to store the rowid along with the REF value in ref_column or ref_attribute. Storing the rowid with the REF value can improve the performance of dereferencing operations, but will also use more space. Default storage of REF values is without rowids. Restrictions on Rowid Constraints Rowid constraints are subject to the following restrictions: ■ You cannot define a rowid constraint for the REF elements of a VARRAY column. ■ You cannot subsequently drop a rowid constraint from a REF column. ■ If the REF column or attribute is scoped, then this clause is ignored and the rowid is not stored with the REF value. Referential Integrity Constraints on REF Columns The references_clause of the ref_constraint syntax lets you define a foreign key constraint on the REF column. This clause also implicitly restricts the scope of the REF column or attribute to the referenced table. However, whereas a foreign key constraint on a non-REF column references an actual column in the parent table, a foreign key constraint on a REF column references the implicit object identifier column of the parent table. If you do not specify a constraint name, then Oracle generates a system name for the constraint of the form SYS_Cn. If you add a referential integrity constraint to an existing REF column that is already scoped, then the referenced table must be the same as the scope table of the REF column. If you later drop the referential integrity constraint, then the REF column will remain scoped to the referenced table. As is the case for foreign key constraints on other types of columns, you can use the references_clause alone for inline declaration. For out-of-line declaration you must also specify the FOREIGN KEY keywords plus one or more REF columns or attributes. Restrictions on Foreign Key Constraints on REF Columns Foreign key constraints on REF columns have the following additional restrictions: See Also: the function DEREF on page 5-56 for an example of dereferencing See Also: Oracle Database Application Developer's Guide - Object-Relational Features for more information on object identifiers
- 454. constraint 8-14 Oracle Database SQL Reference ■ Oracle implicitly adds a scope constraint when you add a referential integrity constraint to an existing unscoped REF column. Therefore, all the restrictions that apply for scope constraints also apply in this case. ■ You cannot specify a column after the object name in the references_clause. Specifying Constraint State As part of constraint definition, you can specify how and when Oracle should enforce the constraint. constraint_state You can use the constraint_state with both inline and out-of-line specification. You can specify the clauses of constraint_state in any order, but you can specify each clause only once. DEFERRABLE Clause The DEFERRABLE and NOT DEFERRABLE parameters indicate whether or not, in subsequent transactions, constraint checking can be deferred until the end of the transaction using the SET CONSTRAINT(S) statement. If you omit this clause, then the default is NOT DEFERRABLE. ■ Specify NOT DEFERRABLE to indicate that in subsequent transactions you cannot use the SET CONSTRAINT[S] clause to defer checking of this constraint until the transaction is committed. The checking of a NOT DEFERRABLE constraint can never be deferred to the end of the transaction. If you declare a new constraint NOT DEFERRABLE, then it must be valid at the time the CREATE TABLE or ALTER TABLE statement is committed or the statement will fail. ■ Specify DEFERRABLE to indicate that in subsequent transactions you can use the SET CONSTRAINT[S] clause to defer checking of this constraint until after the transaction is committed. This setting in effect lets you disable the constraint temporarily while making changes to the database that might violate the constraint until all the changes are complete. You cannot alter the deferrability of a constraint. That is, whether you specify either of these parameters, or make the constraint NOT DEFERRABLE implicitly by specifying neither of them, you cannot specify this clause in an ALTER TABLE statement. You must drop the constraint and re-create it. Restriction on [NOT] DEFERRABLE You cannot specify either of these parameters for a view constraint. INITIALLY Clause The INITIALLY clause establishes the default checking behavior for constraints that are DEFERRABLE. The INITIALLY setting can be overridden by a SET CONSTRAINT(S) statement in a subsequent transaction. ■ Specify INITIALLY IMMEDIATE to indicate that Oracle should check this constraint at the end of each subsequent SQL statement. If you do not specify INITIALLY at all, then the default is INITIALLY IMMEDIATE. See Also: ■ SET CONSTRAINT[S] on page 19-48 for information on setting constraint checking for a transaction ■ Oracle Database Administrator's Guide and Oracle Database Concepts for more information about deferred constraints ■ "DEFERRABLE Constraint Examples" on page 8-25
- 455. constraint Common SQL DDL Clauses 8-15 If you declare a new constraint INITIALLY IMMEDIATE, then it must be valid at the time the CREATE TABLE or ALTER TABLE statement is committed or the statement will fail. ■ Specify INITIALLY DEFERRED to indicate that Oracle should check this constraint at the end of subsequent transactions. This clause is not valid if you have declared the constraint to be NOT DEFERRABLE, because a NOT DEFERRABLE constraint is automatically INITIALLY IMMEDIATE and cannot ever be INITIALLY DEFERRED. VALIDATE | NOVALIDATE The behavior of VALIDATE and NOVALIDATE always depends on whether the constraint is enabled or disabled, either explicitly or by default. Therefore they are described in the context of "ENABLE Clause" on page 8-15 and "DISABLE Clause" on page 8-15. ENABLE Clause Specify ENABLE if you want the constraint to be applied to the data in the table. If you enable a unique or primary key constraint, and if no index exists on the key, then Oracle Database creates a unique index. Unless you specify KEEP INDEX when subsequently disabling the constraint, this index is dropped and the database rebuilds the index every time the constraint is reenabled. You can also avoid rebuilding the index and eliminate redundant indexes by creating new primary key and unique constraints initially disabled. Then create (or use existing) nonunique indexes to enforce the constraint. Oracle does not drop a nonunique index when the constraint is disabled, so subsequent ENABLE operations are facilitated. ■ ENABLE VALIDATE specifies that all old and new data also complies with the constraint. An enabled validated constraint guarantees that all data is and will continue to be valid. If any row in the table violates the integrity constraint, the constraint remains disabled and Oracle returns an error. If all rows comply with the constraint, Oracle enables the constraint. Subsequently, if new data violates the constraint, Oracle does not execute the statement and returns an error indicating the integrity constraint violation. If you place a primary key constraint in ENABLE VALIDATE mode, the validation process will verify that the primary key columns contain no nulls. To avoid this overhead, mark each column in the primary key NOT NULL before entering data into the column and before enabling the primary key constraint of the table. ■ ENABLE NOVALIDATE ensures that all new DML operations on the constrained data comply with the constraint. This clause does not ensure that existing data in the table complies with the constraint and therefore does not require a table lock. If you specify neither VALIDATE nor NOVALIDATE, the default is VALIDATE. If you change the state of any single constraint from ENABLE NOVALIDATE to ENABLE VALIDATE, the operation can be performed in parallel, and does not block reads, writes, or other DDL operations. Restriction on the ENABLE Clause You cannot enable a foreign key that references a disabled unique or primary key. DISABLE Clause Specify DISABLE to disable the integrity constraint. Disabled integrity constraints appear in the data dictionary along with enabled constraints. If
- 456. constraint 8-16 Oracle Database SQL Reference you do not specify this clause when creating a constraint, Oracle automatically enables the constraint. ■ DISABLE VALIDATE disables the constraint and drops the index on the constraint, but keeps the constraint valid. This feature is most useful in data warehousing situations, because it lets you load large amounts of data while also saving space by not having an index. This setting lets you load data from a nonpartitioned table into a partitioned table using the exchange_partition_clause of the ALTER TABLE statement or using SQL*Loader. All other modifications to the table (inserts, updates, and deletes) by other SQL statements are disallowed. ■ DISABLE NOVALIDATE signifies that Oracle makes no effort to maintain the constraint (because it is disabled) and cannot guarantee that the constraint is true (because it is not being validated). You cannot drop a table whose primary key is being referenced by a foreign key even if the foreign key constraint is in DISABLE NOVALIDATE state. Further, the optimizer can use constraints in DISABLE NOVALIDATE state. If you specify neither VALIDATE nor NOVALIDATE, then the default is NOVALIDATE. If you disable a unique or primary key constraint that is using a unique index, then Oracle drops the unique index. Please refer to the CREATE TABLE enable_disable_clause on page 16-45 for additional notes and restrictions. RELY Clause RELY and NORELY are valid only when you are modifying an existing constraint (that is, in the ALTER TABLE ... MODIFY constraint syntax). These parameters specify whether a constraint in NOVALIDATE mode is to be taken into account for query rewrite. Specify RELY to activate an existing constraint in NOVALIDATE mode for query rewrite in an unenforced query rewrite integrity mode. The constraint is in NOVALIDATE mode, so Oracle does not enforce it. The default is NORELY. Unenforced constraints are generally useful only with materialized views and query rewrite. Depending on the QUERY_REWRITE_INTEGRITY mode, query rewrite can use only constraints that are in VALIDATE mode, or that are in NOVALIDATE mode with the RELY parameter set, to determine join information. Restriction on the RELY Clause You cannot set a nondeferrable NOT NULL constraint to RELY. Using Indexes to Enforce Constraints When defining the state of a unique or primary key constraint, you can specify an index for Oracle to use to enforce the constraint, or you can instruct Oracle to create the index used to enforce the constraint. See Also: Oracle Database Data Warehousing Guide for more information on using this setting See Also: Oracle Database Performance Tuning Guide for information on when to use this setting See Also: Oracle Database Data Warehousing Guide for more information on materialized views and query rewrite
- 457. constraint Common SQL DDL Clauses 8-17 using_index_clause You can specify the using_index_clause only when enabling unique or primary key constraints. You can specify the clauses of the using_ index_clause in any order, but you can specify each clause only once. ■ If you specify schema.index, then Oracle attempts to enforce the constraint using the specified index. If Oracle cannot find the index or cannot use the index to enforce the constraint, then Oracle returns an error. ■ If you specify the create_index_statement, then Oracle attempts to create the index and use it to enforce the constraint. If Oracle cannot create the index or cannot use the index to enforce the constraint, then Oracle returns an error. ■ If you neither specify an existing index nor create a new index, then Oracle creates the index. In this case: – The index receives the same name as the constraint. – If table is partitioned, then you can specify a locally or globally partitioned index for the unique or primary key constraint. Restrictions on the using_index_clause The following restrictions apply to the using_index_clause: ■ You cannot specify this clause for a view constraint. ■ You cannot specify this clause for a NOT NULL, foreign key, or check constraint. ■ You cannot specify an index (schema.index) or create an index (create_ index_statement) when enabling the primary key of an index-organized table. ■ You cannot specify the domain_index_clause of index_properties or the parallel_clause of index_attributes. Handling Constraint Exceptions When defining the state of a constraint, you can specify a table into which Oracle places the rowids of all rows violating the constraint. exceptions_clause Use the exceptions_clause syntax to define exception handling. If you omit schema, then Oracle assumes the exceptions table is in your own schema. If you omit this clause altogether, then Oracle assumes that the table is named EXCEPTIONS. The EXCEPTIONS table or the table you specify must exist on your local database. You can create the EXCEPTIONS table using one of these scripts: ■ UTLEXCPT.SQL uses physical rowids. Therefore it can accommodate rows from conventional tables but not from index-organized tables. (See the Note that follows.) ■ UTLEXPT1.SQL uses universal rowids, so it can accommodate rows from both conventional and index-organized tables. See Also: ■ CREATE INDEX on page 14-58 for a description of index_ attributes, the global_partitioned_index and local_partitioned_index clauses, and for a description of NOSORT and the logging_ clause in relation to indexes ■ physical_attributes_clause on page 8-42 and PCTFREE parameters and storage_clause on page 8-46 ■ "Explicit Index Control Example" on page 8-25
- 458. constraint 8-18 Oracle Database SQL Reference If you create your own exceptions table, then it must follow the format prescribed by one of these two scripts. If you are collecting exceptions from index-organized tables based on primary keys (rather than universal rowids), then you must create a separate exceptions table for each index-organized table to accommodate its primary-key storage. You create multiple exceptions tables with different names by modifying and resubmitting the script. Restrictions on the exceptions_clause The following restrictions apply to the exceptions_clause: ■ You cannot specify this clause for a view constraint. ■ You cannot specify this clause in a CREATE TABLE statement, because no rowids exist until after the successful completion of the statement. View Constraints Oracle does not enforce view constraints. However, operations on views are subject to the integrity constraints defined on the underlying base tables. This means that you can enforce constraints on views through constraints on base tables. Notes on View Constraints View constraints are a subset of table constraints and are subject to the following restrictions: ■ You can specify only unique, primary key, and foreign key constraints on views. However, you can define the view using the WITH CHECK OPTION clause, which is equivalent to specifying a check constraint for the view. ■ View constraints are supported only in DISABLE NOVALIDATE mode. You cannot specify any other mode. You must specify the keyword DISABLE when you declare the view constraint. You need not specify NOVALIDATE explicitly, as it is the default. ■ The RELY and NORELY parameters are optional. View constraints, because they are unenforced, are usually specified with the RELY parameter to make them more useful. The RELY or NORELY keyword must precede the DISABLE keyword. Please refer to "RELY Clause" on page 8-16 for more information. ■ Because view constraints are not enforced directly, you cannot specify INITIALLY DEFERRED or DEFERRABLE. ■ You cannot specify the using_index_clause, the exceptions_clause clause, or the ON DELETE clause of the references_clause. ■ You cannot define view constraints on attributes of an object column. See Also: ■ Oracle Database Upgrade Guide for compatibility issues related to the use of these scripts ■ The DBMS_IOT package in Oracle Database PL/SQL Packages and Types Reference for information on the SQL scripts ■ Oracle Database Performance Tuning Guide for information on eliminating migrated and chained rows
- 459. constraint Common SQL DDL Clauses 8-19 Examples Unique Key Example The following statement is a variation of the statement that created the sample table sh.promotions. It defines inline and implicitly enables a unique key on the promo_id column (other constraints are not shown): CREATE TABLE promotions_var1 ( promo_id NUMBER(6) CONSTRAINT promo_id_u UNIQUE , promo_name VARCHAR2(20) , promo_category VARCHAR2(15) , promo_cost NUMBER(10,2) , promo_begin_date DATE , promo_end_date DATE ) ; The constraint promo_id_u identifies the promo_id column as a unique key. This constraint ensures that no two promotions in the table have the same ID. However, the constraint does allow promotions without identifiers. Alternatively, you can define and enable this constraint out of line: CREATE TABLE promotions_var2 ( promo_id NUMBER(6) , promo_name VARCHAR2(20) , promo_category VARCHAR2(15) , promo_cost NUMBER(10,2) , promo_begin_date DATE , promo_end_date DATE , CONSTRAINT promo_id_u UNIQUE (promo_id) USING INDEX PCTFREE 20 TABLESPACE stocks STORAGE (INITIAL 8K NEXT 6K) ); The preceding statement also contains the using_index_clause, which specifies storage characteristics for the index that Oracle creates to enable the constraint. Composite Unique Key Example The following statement defines and enables a composite unique key on the combination of the warehouse_id and warehouse_ name columns of the oe.warehouses table: ALTER TABLE warehouses ADD CONSTRAINT wh_unq UNIQUE (warehouse_id, warehouse_name) USING INDEX PCTFREE 5 EXCEPTIONS INTO wrong_id; The wh_unq constraint ensures that the same combination of warehouse_id and warehouse_name values does not appear in the table more than once. The ADD CONSTRAINT clause also specifies other properties of the constraint: ■ The USING INDEX clause specifies storage characteristics for the index Oracle creates to enable the constraint. ■ The EXCEPTIONS INTO clause causes Oracle to write to the wrong_id table information about any rows currently in the warehouses table that violate the constraint. If the wrong_id exceptions table does not already exist, then this statement will fail. Primary Key Example The following statement is a variation of the statement that created the sample table hr.locations. It creates the locations_demo table and
- 460. constraint 8-20 Oracle Database SQL Reference defines and enables a primary key on the location_id column (other constraints from the hr.locations table are omitted): CREATE TABLE locations_demo ( location_id NUMBER(4) CONSTRAINT loc_id_pk PRIMARY KEY , street_address VARCHAR2(40) , postal_code VARCHAR2(12) , city VARCHAR2(30) , state_province VARCHAR2(25) , country_id CHAR(2) ) ; The loc_id_pk constraint, specified inline, identifies the location_id column as the primary key of the locations_demo table. This constraint ensures that no two locations in the table have the same location number and that no location identifier is NULL. Alternatively, you can define and enable this constraint out of line: CREATE TABLE locations_demo ( location_id NUMBER(4) , street_address VARCHAR2(40) , postal_code VARCHAR2(12) , city VARCHAR2(30) , state_province VARCHAR2(25) , country_id CHAR(2) , CONSTRAINT loc_id_pk PRIMARY KEY (location_id)); NOT NULL Example The following statement alters the locations_demo table (created in "Primary Key Example" on page 8-19) to define and enable a NOT NULL constraint on the country_id column: ALTER TABLE locations_demo MODIFY (country_id CONSTRAINT country_nn NOT NULL); The constraint country_nn ensures that no location in the table has a null country_ id. Composite Primary Key Example The following statement defines a composite primary key on the combination of the prod_id and cust_id columns of the sample table sh.sales: ALTER TABLE sales ADD CONSTRAINT sales_pk PRIMARY KEY (prod_id, cust_id) DISABLE; This constraint identifies the combination of the prod_id and cust_id columns as the primary key of the sales table. The constraint ensures that no two rows in the table have the same combination of values for the prod_id column and cust_id columns. The constraint clause (PRIMARY KEY) also specifies the following properties of the constraint: ■ The constraint definition does not include a constraint name, so Oracle generates a name for the constraint. ■ The DISABLE clause causes Oracle to define the constraint but not enable it. Foreign Key Constraint Example The following statement creates the dept_20 table and defines and enables a foreign key on the department_id column that references the primary key on the department_id column of the departments table:
- 461. constraint Common SQL DDL Clauses 8-21 CREATE TABLE dept_20 (employee_id NUMBER(4), last_name VARCHAR2(10), job_id VARCHAR2(9), manager_id NUMBER(4), hire_date DATE, salary NUMBER(7,2), commission_pct NUMBER(7,2), department_id CONSTRAINT fk_deptno REFERENCES departments(department_id) ); The constraint fk_deptno ensures that all departments given for employees in the dept_20 table are present in the departments table. However, employees can have null department numbers, meaning they are not assigned to any department. To ensure that all employees are assigned to a department, you could create a NOT NULL constraint on the department_id column in the dept_20 table in addition to the REFERENCES constraint. Before you define and enable this constraint, you must define and enable a constraint that designates the department_id column of the departments table as a primary or unique key. The foreign key constraint definition does not use the FOREIGN KEY clause, because the constraint is defined inline. The datatype of the department_id column is not needed, because Oracle automatically assigns to this column the datatype of the referenced key. The constraint definition identifies both the parent table and the columns of the referenced key. Because the referenced key is the primary key of the parent table, the referenced key column names are optional. Alternatively, you can define this foreign key constraint out of line: CREATE TABLE dept_20 (employee_id NUMBER(4), last_name VARCHAR2(10), job_id VARCHAR2(9), manager_id NUMBER(4), hire_date DATE, salary NUMBER(7,2), commission_pct NUMBER(7,2), department_id, CONSTRAINT fk_deptno FOREIGN KEY (department_id) REFERENCES departments(department_id) ); The foreign key definitions in both variations of this statement omit the ON DELETE clause, causing Oracle to prevent the deletion of a department if any employee works in that department. ON DELETE Example This statement creates the dept_20 table, defines and enables two referential integrity constraints, and uses the ON DELETE clause: CREATE TABLE dept_20 (employee_id NUMBER(4) PRIMARY KEY, last_name VARCHAR2(10), job_id VARCHAR2(9), manager_id NUMBER(4) CONSTRAINT fk_mgr REFERENCES employees ON DELETE SET NULL, hire_date DATE, salary NUMBER(7,2),
- 462. constraint 8-22 Oracle Database SQL Reference commission_pct NUMBER(7,2), department_id NUMBER(2) CONSTRAINT fk_deptno REFERENCES departments(department_id) ON DELETE CASCADE ); Because of the first ON DELETE clause, if manager number 2332 is deleted from the employees table, then Oracle sets to null the value of manager_id for all employees in the dept_20 table who previously had manager 2332. Because of the second ON DELETE clause, Oracle cascades any deletion of a department_id value in the departments table to the department_id values of its dependent rows of the dept_20 table. For example, if Department 20 is deleted from the departments table, then Oracle deletes all of the employees in Department 20 from the dept_20 table. Composite Foreign Key Constraint Example The following statement defines and enables a foreign key on the combination of the employee_id and hire_date columns of the dept_20 table: ALTER TABLE dept_20 ADD CONSTRAINT fk_empid_hiredate FOREIGN KEY (employee_id, hire_date) REFERENCES hr.job_history(employee_id, start_date) EXCEPTIONS INTO wrong_emp; The constraint fk_empid_hiredate ensures that all the employees in the dept_20 table have employee_id and hire_date combinations that exist in the employees table. Before you define and enable this constraint, you must define and enable a constraint that designates the combination of the employee_id and hire_date columns of the employees table as a primary or unique key. The EXCEPTIONS INTO clause causes Oracle to write information to the wrong_emp table about any rows in the dept_20 table that violate the constraint. If the wrong_ emp exceptions table does not already exist, then this statement will fail. Check Constraint Examples The following statement creates a divisions table and defines a check constraint in each column of the table: CREATE TABLE divisions (div_no NUMBER CONSTRAINT check_divno CHECK (div_no BETWEEN 10 AND 99) DISABLE, div_name VARCHAR2(9) CONSTRAINT check_divname CHECK (div_name = UPPER(div_name)) DISABLE, office VARCHAR2(10) CONSTRAINT check_office CHECK (office IN ('DALLAS','BOSTON', 'PARIS','TOKYO')) DISABLE); Each constraint restricts the values of the column in which it is defined: ■ check_divno ensures that no division numbers are less than 10 or greater than 99. ■ check_divname ensures that all division names are in uppercase. ■ check_office restricts office locations to Dallas, Boston, Paris, or Tokyo. Because each CONSTRAINT clause contains the DISABLE clause, Oracle only defines the constraints and does not enable them.
- 463. constraint Common SQL DDL Clauses 8-23 The following statement creates the dept_20 table, defining out of line and implicitly enabling a check constraint: CREATE TABLE dept_20 (employee_id NUMBER(4) PRIMARY KEY, last_name VARCHAR2(10), job_id VARCHAR2(9), manager_id NUMBER(4), salary NUMBER(7,2), commission_pct NUMBER(7,2), department_id NUMBER(2), CONSTRAINT check_sal CHECK (salary * commission_pct <= 5000)); This constraint uses an inequality condition to limit an employee's total commission, the product of salary and commission_pct, to $5000: ■ If an employee has non-null values for both salary and commission, then the product of these values must not exceed $5000 to satisfy the constraint. ■ If an employee has a null salary or commission, then the result of the condition is unknown and the employee automatically satisfies the constraint. Because the constraint clause in this example does not supply a constraint name, Oracle generates a name for the constraint. The following statement defines and enables a primary key constraint, two foreign key constraints, a NOT NULL constraint, and two check constraints: CREATE TABLE order_detail (CONSTRAINT pk_od PRIMARY KEY (order_id, part_no), order_id NUMBER CONSTRAINT fk_oid REFERENCES oe.orders(order_id), part_no NUMBER CONSTRAINT fk_pno REFERENCES oe.product_information(product_id), quantity NUMBER CONSTRAINT nn_qty NOT NULL CONSTRAINT check_qty CHECK (quantity > 0), cost NUMBER CONSTRAINT check_cost CHECK (cost > 0) ); The constraints enable the following rules on table data: ■ pk_od identifies the combination of the order_id and part_no columns as the primary key of the table. To satisfy this constraint, no two rows in the table can contain the same combination of values in the order_id and the part_no columns, and no row in the table can have a null in either the order_id or the part_no column. ■ fk_oid identifies the order_id column as a foreign key that references the order_id column in the orders table in the sample schema oe. All new values added to the column order_detail.order_id must already appear in the column oe.orders.order_id. ■ fk_pno identifies the product_id column as a foreign key that references the product_id column in the product_information table owned by oe. All new values added to the column order_detail.product_id must already appear in the column oe.product_information.product_id. ■ nn_qty forbids nulls in the quantity column.
- 464. constraint 8-24 Oracle Database SQL Reference ■ check_qty ensures that values in the quantity column are always greater than zero. ■ check_cost ensures the values in the cost column are always greater than zero. This example also illustrates the following points about constraint clauses and column definitions: ■ Out-of-line constraint definition can appear before or after the column definitions. In this example, the out-of-line definition of the pk_od constraint precedes the column definitions. ■ A column definition can contain multiple inline constraint definitions. In this example, the definition of the quantity column contains the definitions of both the nn_qty and check_qty constraints. ■ A table can have multiple CHECK constraints. Multiple CHECK constraints, each with a simple condition enforcing a single business rule, are preferable to a single CHECK constraint with a complicated condition enforcing multiple business rules. When a constraint is violated, Oracle returns an error identifying the constraint. Such an error more precisely identifies the violated business rule if the identified constraint enables a single business rule. Attribute-Level Constraints Example The following example guarantees that a value exists for both the first_name and last_name attributes of the name column in the students table: CREATE TYPE person_name AS OBJECT (first_name VARCHAR2(30), last_name VARCHAR2(30)); / CREATE TABLE students (name person_name, age INTEGER, CHECK (name.first_name IS NOT NULL AND name.last_name IS NOT NULL)); REF Constraint Examples The following example creates a duplicate of the sample schema object type cust_address_typ, and then creates a table containing a REF column with a SCOPE constraint: CREATE TYPE cust_address_typ_new AS OBJECT ( street_address VARCHAR2(40) , postal_code VARCHAR2(10) , city VARCHAR2(30) , state_province VARCHAR2(10) , country_id CHAR(2) ); / CREATE TABLE address_table OF cust_address_typ_new; CREATE TABLE customer_addresses ( add_id NUMBER, address REF cust_address_typ_new SCOPE IS address_table); The following example creates the same table but with a referential integrity constraint on the REF column that references the object identifier column of the parent table: CREATE TABLE customer_addresses ( add_id NUMBER, address REF cust_address_typ REFERENCES address_table);
- 465. constraint Common SQL DDL Clauses 8-25 The following example uses the type department_typ and the table departments_ obj_t, created in "Creating Object Tables: Examples" on page 16-59. A table with a scoped REF is then created. CREATE TABLE employees_obj ( e_name VARCHAR2(100), e_number NUMBER, e_dept REF department_typ SCOPE IS departments_obj_t ); The following statement creates a table with a REF column which has a referential integrity constraint defined on it: CREATE TABLE employees_obj ( e_name VARCHAR2(100), e_number NUMBER, e_dept REF department_typ REFERENCES departments_obj_t); Explicit Index Control Example The following statement shows another way to create a unique (or primary key) constraint that gives you explicit control over the index (or indexes) Oracle uses to enforce the constraint: CREATE TABLE promotions_var3 ( promo_id NUMBER(6) , promo_name VARCHAR2(20) , promo_category VARCHAR2(15) , promo_cost NUMBER(10,2) , promo_begin_date DATE , promo_end_date DATE , CONSTRAINT promo_id_u UNIQUE (promo_id, promo_cost) USING INDEX (CREATE UNIQUE INDEX promo_ix1 ON promotions_var3 (promo_id, promo_cost)) , CONSTRAINT promo_id_u2 UNIQUE (promo_cost, promo_id) USING INDEX promo_ix1); This example also shows that you can create an index for one constraint and use that index to create and enable another constraint in the same statement. DEFERRABLE Constraint Examples The following statement creates table games with a NOT DEFERRABLE INITIALLY IMMEDIATE constraint check (by default) on the scores column: CREATE TABLE games (scores NUMBER CHECK (scores >= 0)); To define a unique constraint on a column as INITIALLY DEFERRED DEFERRABLE, issue the following statement: CREATE TABLE games (scores NUMBER, CONSTRAINT unq_num UNIQUE (scores) INITIALLY DEFERRED DEFERRABLE);
- 466. deallocate_unused_clause 8-26 Oracle Database SQL Reference deallocate_unused_clause Purpose Use the deallocate_unused_clause to explicitly deallocate unused space at the end of a database object segment and make the space available for other segments in the tablespace. You can deallocate unused space using the following statements: ■ ALTER CLUSTER (see ALTER CLUSTER on page 10-5) ■ ALTER INDEX: to deallocate unused space from the index, an index partition, or an index subpartition (see ALTER INDEX on page 10-64) ■ ALTER MATERIALIZED VIEW: to deallocate unused space from the overflow segment of an index-organized materialized view (see ALTER MATERIALIZED VIEW on page 11-2) ■ ALTER TABLE: to deallocate unused space from the table, a table partition, a table subpartition, the mapping table of an index-organized table, the overflow segment of an index-organized table, or a LOB storage segment (see ALTER TABLE on page 12-2) Syntax deallocate_unused_clause::= (size_clause::= on page 8-45) Semantics This section describes the semantics of the deallocate_unused_clause. For additional information, refer to the SQL statement in which you set or reset this clause for a particular database object. You cannot specify both the deallocate_unused_clause and the allocate_ extent_clause in the same statement. Oracle Database frees only unused space above the high water mark (that is, the point beyond which database blocks have not yet been formatted to receive data). Oracle deallocates unused space beginning from the end of the object and moving toward the beginning of the object to the high water mark. If an extent is completely contained in the deallocation, then the whole extent is freed for reuse. If an extent is partially contained in the deallocation, then the used part up to the high water mark becomes the extent, and the remaining unused space is freed for reuse. Oracle credits the amount of the released space to the user quota for the tablespace in which the deallocation occurs. The exact amount of space freed depends on the values of the INITIAL, MINEXTENTS, and NEXT storage parameters. Please refer to the storage_clause on page 8-46 for a description of these parameters. DEALLOCATE UNUSED KEEP size_clause
- 467. deallocate_unused_clause Common SQL DDL Clauses 8-27 KEEP integer Specify the number of bytes above the high water mark that the segment of the database object is to have after deallocation. ■ If you omit KEEP and the high water mark is above the size of INITIAL and MINEXTENTS, then all unused space above the high water mark is freed. When the high water mark is less than the size of INITIAL or MINEXTENTS, then all unused space above MINEXTENTS is freed. ■ If you specify KEEP, then the specified amount of space is kept and the remaining space is freed. When the remaining number of extents is less than MINEXTENTS, then Oracle adjusts MINEXTENTS to the new number of extents. If the initial extent becomes smaller than INITIAL, then Oracle adjusts INITIAL to the new size. ■ In either case, Oracle sets the value of the NEXT storage parameter to the size of the last extent that was deallocated.
- 468. file_specification 8-28 Oracle Database SQL Reference file_specification Purpose Use one of the file_specification forms to specify a file as a datafile or tempfile, or to specify a group of one or more files as a redo log file group. If you are storing your files in Automatic Storage Management disk groups, then you can further specify the file as a disk group file. A file_specification can appear in the following statements: ■ CREATE CONTROLFILE (see CREATE CONTROLFILE on page 14-12) ■ CREATE DATABASE (see CREATE DATABASE on page 14-18) ■ ALTER DATABASE (see ALTER DATABASE on page 10-9) ■ CREATE TABLESPACE (see CREATE TABLESPACE on page 16-61) ■ ALTER TABLESPACE (see ALTER TABLESPACE on page 12-79) ■ ALTER DISKGROUP (see ALTER DISKGROUP on page 10-48) Prerequisites You must have the privileges necessary to issue the statement in which the file specification appears. Syntax file_specification::= datafile_tempfile_spec::= (size_clause::= on page 8-45) redo_log_file_spec::= (size_clause::= on page 8-45) datafile_tempfile_spec redo_log_file_spec ’ filename ASM_filename ’ SIZE size_clause REUSE autoextend_clause ’ filename ASM_filename ’ ( ’ filename ASM_filename ’ , ) SIZE size_clause REUSE
- 469. file_specification Common SQL DDL Clauses 8-29 ASM_filename::= fully_qualified_file_name::= numeric_file_name::= incomplete_file_name::= alias_file_name::= autoextend_clause::= (size_clause::= on page 8-45) maxsize_clause::= (size_clause::= on page 8-45) Semantics This section describes the semantics of file_specification. For additional information, refer to the SQL statement in which you specify a datafile, tempfile, redo log file, or Automatic Storage Management disk group or disk group file. datafile_tempfile_spec Use this clause to specify the attributes of datafiles and tempfiles if your database storage is in a file system or on raw devices or in Automatic Storage Management disk groups. fully_qualified_file_name numeric_file_name incomplete_file_name alias_file_name + diskgroup_name / db_name / file_type / file_type_tag . filenumber . incarnation_number + diskgroup_name . filenumber . incarnation_number + diskgroup_name ( template_name ) + diskgroup_name ( template_name ) / alias_name AUTOEXTEND OFF ON NEXT size_clause maxsize_clause MAXSIZE UNLIMITED size_clause
- 470. file_specification 8-30 Oracle Database SQL Reference redo_log_file_spec Use this clause to specify the attributes of redo log files if your database storage is in a file system or on raw devices or in Automatic Storage Management disk groups. filename Use filename for files stored in a file system or on raw devices. The filename can specify either a new file or an existing file. For a new file: ■ If you are not using Oracle-managed files, then you must specify both filename and the SIZE clause or the statement fails. When you specify a filename without a size, Oracle attempts to reuse an existing file and returns an error if the file does not exist. ■ If you are using Oracle-managed files, then filename is optional, as are the remaining clauses of the specification. In this case, Oracle Database creates a unique name for the file and saves it in the directory specified by either the DB_ RECOVERY_FILE_DEST (for logfiles and control files), the DB_CREATE_FILE_ DEST initialization parameter (for any type of file) or by the DB_CREATE_ ONLINE_LOG_DEST_n initialization parameter (which takes precedence over DB_ CREATE_FILE_DEST and DB_RECOVERY_FILE_DEST for log files). For an existing file, specify the name of either a datafile, tempfile, or a redo log file member. The filename can contain only single-byte characters from 7-bit ASCII or EBCDIC character sets. Multibyte characters are not valid. A redo log file group can have one or more members (copies). Each filename must be fully specified according to the conventions for your operating system. The way the database interprets filename also depends on whether you specify it with the SIZE and REUSE clauses. ■ If you specify filename only, or with the REUSE clause but without the SIZE clause, then the file must already exist. ■ If you specify filename with SIZE but without REUSE, the file must be a new file. ■ If you specify filename with both SIZE and REUSE, then the file can be either new or existing. If the file exists, it is reused with the new size. If it does not exist, the database ignores the REUSE keyword and creates a new file of the specified size. ASM_filename Use a form of ASM_filename for files stored in Automatic Storage Management disk groups. You can create or refer to datafiles, tempfiles, and redo log files with this syntax. All forms of ASM_filename begin with the plus sign (+) followed by the name of the disk group. You can determine the names of all Automatic Storage Management disk groups by querying the V$ASM_DISKGROUP view. See Also: Oracle Database Administrator's Guide for more information on Oracle-managed files, "Specifying a Datafile: Example" on page 8-35, and "Specifying a Log File: Example" on page 8-34 See Also: Oracle Database Administrator's Guide for information on using Automatic Storage Management
- 471. file_specification Common SQL DDL Clauses 8-31 fully_qualified_file_name When you create a file in an Automatic Storage Management disk group, the file receives a system-generated fully qualified Automatic Storage Management filename. You can use this form only when referring to an existing Automatic Storage Management file. Therefore, if you are using this form during file creation, you must also specify REUSE. ■ db_name is the value of the DB_UNIQUE_NAME initialization parameter. This name is equivalent to the name of the database on which the file resides, but the parameter distinguishes between primary and standby databases, if both exist. ■ file_type and file_type_tag indicate the type of database file. The table that follows lists all of the file types and their corresponding Automatic Storage Management tags. ■ filenumber and incarnation_number are system-generated identifiers to guarantee uniqueness. You can determine the fully qualified names of Automatic Storage Management files by querying the dynamic performance view appropriate for the file type (for example V$DATAFILE for datafiles, V$CONTROLFILE for control files, and so on). You can also obtain the filenumber and incarnation_number portions of the fully qualified names by querying the V$ASM_FILE view. Table 8–1 Oracle File Types and Automatic Storage Management File Type Tags Automatic Storage Management file_type Description Automatic Storage Management file_type_ tag Comments CONTROLFILE Control files and backup control files Current Backup — DATAFILE Datafiles and datafile copies tsname Tablespace into which the file is added ONLINELOG Online logs group_group# — ARCHIVELOG Archive logs thread_thread#_seq_ sequence# — TEMPFILE Tempfiles tsname Tablespace into which the file is added BACKUPSET Datafile and archive log backup pieces; datafile incremental backup pieces hasspfile_timestamp hasspfile can take one of two values: s indicates that the backup set includes the spfile; n indicates that the backup set does not include the spfile. PARAMETERFILE Persistent parameter files spfile — DAATAGUARDCONFIG Data Guard configuration file db_unique_name Data Guard tries to use the service provider name if it is set. Otherwise the tag defaults to DRCname. FLASHBACK Flashback logs log_log# — CHANGETRACKING Block change tracking data ctf Used during incremental backups
- 472. file_specification 8-32 Oracle Database SQL Reference numeric_file_name A numeric Automatic Storage Management filename is similar to a fully qualified filename except that it uses only the unique filenumber.incarnation_number string. You can use this form only to refer to an existing file. Therefore, if you are using this form during file creation, you must also specify REUSE. incomplete_file_name Incomplete Automatic Storage Management filenames are used during file creation only. If you specify the disk group name alone, Automatic Storage Management uses the appropriate default template for the file type. For example, if you are creating a datafile in a CREATE TABLESPACE statement, Automatic Storage Management uses the default DATAFILE template to create an Automatic Storage Management datafile. If you specify the disk group name with a template, Automatic Storage Management uses the specified template to create the file. In both cases, Automatic Storage Management also creates a fully qualified filename. template_name A template is a named collection of attributes. You can create templates and apply them to files in a disk group. You can determine the names of all Automatic Storage Management template names by querying the V$ASM_TEMPLATE data dictionary view. Please refer to diskgroup_template_clauses on page 10-55 for instructions on creating Automatic Storage Management templates. You can specify template only during file creation. It appears in the incomplete and alias name forms of the ASM_filename diagram: ■ If you specify template immediately after the disk group name, then Automatic Storage Management uses the specified template to create the file, and gives the file a fully qualified filename. ■ If you specify template after specifying an alias, then Automatic Storage Management uses the specified template to create the file, gives the file a fully qualified filename, and also creates the alias so that you can subsequently use it to refer to the file. If the alias you specify refers to an existing file, then Automatic Storage Management ignores the template specification unless you also specify REUSE. DUMPSET Data Pump dumpset user_obj#_file# Dump set files encode the user name, the job number that created the dump set, and the file number as part of the tag. XTRANSPORT Datafile convert tsname — AUTOBACKUP Automatic backup files hasspfile_timestamp hasspfile can take one of two values: s indicates that the backup set includes the spfile; n indicates that the backup set does not include the spfile. See Also: diskgroup_template_clauses on page 10-55 for information about the default templates Table 8–1 (Cont.) (Cont.) Oracle File Types and Automatic Storage Management File Type Tags Automatic Storage Management file_type Description Automatic Storage Management file_type_ tag Comments
- 473. file_specification Common SQL DDL Clauses 8-33 alias_file_name An alias is a user-friendly name for an Automatic Storage Management file. You can use alias filenames during file creation or reference. You can specify a template with an alias, but only during file creation. To determine the alias names for Automatic Storage Management files, query the V$ASM_ALIAS data dictionary view. If you are specifying an alias during file creation, please refer to diskgroup_directory_ clauses on page 10-56 and diskgroup_alias_clauses on page 10-57 for instructions on specifying the full alias name. SIZE Clause Specify the size of the file in bytes. Use K, M, G, or T to specify the size in kilobytes, megabytes, gigabytes, or terabytes. ■ For undo tablespaces, you must specify the SIZE clause for each datafile. For other tablespaces, you can omit this parameter if the file already exists, or if you are creating an Oracle-managed file. ■ If you omit this clause when creating an Oracle-managed file, then Oracle creates a 100M file. ■ The size of a tablespace must be one block greater than the sum of the sizes of the objects contained in it. REUSE Specify REUSE to allow Oracle to reuse an existing file. ■ If the file already exists, then Oracle reuses the filename and applies the new size (if you specify SIZE) or retains the original size. ■ If the file does not exist, then Oracle ignores this clause and creates the file. Restriction on the REUSE Clause You cannot specify REUSE unless you have specified filename. Whenever Oracle uses an existing file, the previous contents of the file are lost. autoextend_clause The autoextend_clause is valid for datafiles and tempfiles but not for redo log files. Use this clause to enable or disable the automatic extension of a new or existing datafile or tempfile. If you omit this clause: ■ For Oracle-managed files: – If you specify SIZE, then Oracle Database creates a file of the specified size with AUTOEXTEND disabled. – If you do not specify SIZE, then the database creates a 100M file with AUTOEXTEND enabled. When autoextension is required, the database extends the file by its original size or 100MB, whichever is smaller. You can override this default behavior by specifying the NEXT clause. See Also: Oracle Database Administrator's Guide for information on automatic undo management and undo tablespaces and "Adding a Log File: Example" on page 8-34 See Also: "Adding a Datafile: Example" on page 8-35 and "Adding a Log File: Example" on page 8-34
- 474. file_specification 8-34 Oracle Database SQL Reference ■ For user-managed files, with or without SIZE specified, Oracle creates a file with AUTOEXTEND disabled. ON Specify ON to enable autoextend. OFF Specify OFF to turn off autoextend if is turned on. When you turn off autoextend, the values of NEXT and MAXSIZE are set to zero. If you turn autoextend back on in a subsequent statement, you must reset these values. NEXT Use the NEXT clause to specify the size in bytes of the next increment of disk space to be allocated automatically when more extents are required. The default is the size of one data block. MAXSIZE Use the MAXSIZE clause to specify the maximum disk space allowed for automatic extension of the datafile. UNLIMITED Use the UNLIMITED clause if you do not want to limit the disk space that Oracle can allocate to the datafile or tempfile. Restriction on the autoextend_clause You cannot specify this clause as part of the datafile_tempfile_spec in a CREATE CONTROLFILE statement or in an ALTER DATABASE CREATE DATAFILE clause. Examples Specifying a Log File: Example The following statement creates a database named payable that has two redo log file groups, each with two members, and one datafile: CREATE DATABASE payable LOGFILE GROUP 1 ('diska:log1.log', 'diskb:log1.log') SIZE 50K, GROUP 2 ('diska:log2.log', 'diskb:log2.log') SIZE 50K DATAFILE 'diskc:dbone.dat' SIZE 30M; The first file specification in the LOGFILE clause specifies a redo log file group with the GROUP value 1. This group has members named 'diska:log1.log' and 'diskb:log1.log', each 50 kilobytes in size. The second file specification in the LOGFILE clause specifies a redo log file group with the GROUP value 2. This group has members named 'diska:log2.log' and 'diskb:log2.log', also 50 kilobytes in size. The file specification in the DATAFILE clause specifies a datafile named 'diskc:dbone.dat', 30 megabytes in size. Each file specification specifies a value for the SIZE parameter and omits the REUSE clause, so none of these files can already exist. Oracle must create them. Adding a Log File: Example The following statement adds another redo log file group with two members to the payable database: ALTER DATABASE payable ADD LOGFILE GROUP 3 ('diska:log3.log', 'diskb:log3.log') SIZE 50K REUSE; The file specification in the ADD LOGFILE clause specifies a new redo log file group with the GROUP value 3. This new group has members named 'diska:log3.log' and 'diskb:log3.log', each 50 kilobytes in size. Because the file specification specifies the REUSE clause, each member can (but need not) already exist.
- 475. file_specification Common SQL DDL Clauses 8-35 Specifying a Datafile: Example The following statement creates a tablespace named stocks that has three datafiles: CREATE TABLESPACE stocks DATAFILE 'stock1.dat' SIZE 10M, 'stock2.dat' SIZE 10M, 'stock3.dat' SIZE 10M; The file specifications for the datafiles specify files named 'diskc:stock1.dat', 'diskc:stock2.dat', and 'diskc:stock3.dat'. Adding a Datafile: Example The following statement alters the stocks tablespace and adds a new datafile: ALTER TABLESPACE stocks ADD DATAFILE 'stock4.dat' SIZE 10M REUSE; The file specification specifies a datafile named 'stock4.dat'. If the filename does not exist, then Oracle simply ignores the REUSE keyword. Using a Fully Qualified Automatic Storage Management Datafile Name: Example When using Automatic Storage Management, the following syntax shows how to use the fully_qualified_file_name clause to bring online a datafile in a hypothetical database, testdb: ALTER DATABASE testdb DATAFILE '+dgroup_01/testdb/datafile/system.261.1' ONLINE;
- 476. logging_clause 8-36 Oracle Database SQL Reference logging_clause Purpose The logging_clause lets you specify whether creation of a database object will be logged in the redo log file (LOGGING) or not (NOLOGGING). You can specify the logging_clause in the following statements: ■ CREATE TABLE and ALTER TABLE: for logging of the table, a table partition, a LOB segment, or the overflow segment of an index-organized table (see CREATE TABLE on page 16-6 and ALTER TABLE on page 12-2). ■ CREATE INDEX and ALTER INDEX: for logging of the index or an index partition (see CREATE INDEX on page 14-58 and ALTER INDEX on page 10-64). ■ CREATE MATERIALIZED VIEW and ALTER MATERIALIZED VIEW: for logging of the materialized view, one of its partitions, or a LOB segment (see CREATE MATERIALIZED VIEW on page 15-4 and ALTER MATERIALIZED VIEW on page 11-2). ■ CREATE MATERIALIZED VIEW LOG and ALTER MATERIALIZED VIEW LOG: for logging of the materialized view log or one of its partitions (see CREATE MATERIALIZED VIEW LOG on page 15-25 and ALTER MATERIALIZED VIEW LOG on page 11-15). ■ CREATE TABLESPACE and ALTER TABLESPACE: to set or modify the default logging characteristics for all objects created in the tablespace (see CREATE TABLESPACE on page 16-61 and ALTER TABLESPACE on page 12-79). You can also specify LOGGING or NOLOGGING for the following operations: ■ Rebuilding an index (using CREATE INDEX ... REBUILD) ■ Moving a table (using ALTER TABLE ... MOVE) Syntax logging_clause::= Semantics This section describes the semantics of the logging_clause. For additional information, refer to the SQL statement in which you set or reset logging characteristics for a particular database object. Specify LOGGING if you want the creation of a database object, as well as subsequent inserts into the object, to be logged in the redo log file. Specify NOLOGGING if you do not want these operations to be logged. ■ For a nonpartitioned object, the value specified for this clause is the actual physical attribute of the segment associated with the object. ■ For partitioned objects, the value specified for this clause is the default physical attribute of the segments associated with all partitions specified in the CREATE LOGGING NOLOGGING
- 477. logging_clause Common SQL DDL Clauses 8-37 statement (and in subsequent ALTER ... ADD PARTITION statements), unless you specify the logging attribute in the PARTITION description. If the object for which you are specifying the logging attributes resides in a database or tablespace in force logging mode, then Oracle Database ignores any NOLOGGING setting until the database or tablespace is taken out of force logging mode. If the database is run in archivelog mode, then media recovery from a backup made before the LOGGING operation re-creates the object. However, media recovery from a backup made before the NOLOGGING operation does not re-create the object. The size of a redo log generated for an operation in NOLOGGING mode is significantly smaller than the log generated in LOGGING mode. In NOLOGGING mode, data is modified with minimal logging (to mark new extents INVALID and to record dictionary changes). When applied during media recovery, the extent invalidation records mark a range of blocks as logically corrupt, because the redo data is not fully logged. Therefore, if you cannot afford to lose the database object, then you should take a backup after the NOLOGGING operation. NOLOGGING is supported in only a subset of the locations that support LOGGING. Only the following operations support the NOLOGGING mode: DML: ■ Direct-path INSERT (serial or parallel) resulting either from an INSERT or a MERGE statement. NOLOGGING is not applicable to any UPDATE operations resulting from the MERGE statement. ■ Direct Loader (SQL*Loader) DDL: ■ CREATE TABLE ... AS SELECT ■ CREATE TABLE ... LOB_storage_clause ... LOB_parameters ... NOCACHE | CACHE READS ■ ALTER TABLE ... LOB_storage_clause ... LOB_parameters ... NOCACHE | CACHE READS (to specify logging of newly created LOB columns) ■ ALTER TABLE ... modify_LOB_storage_clause ... modify_LOB_parameters ... NOCACHE | CACHE READS (to change logging of existing LOB columns) ■ ALTER TABLE ... MOVE ■ ALTER TABLE ... (all partition operations that involve data movement) – ALTER TABLE ... ADD PARTITION (hash partition only) – ALTER TABLE ... MERGE PARTITIONS – ALTER TABLE ... SPLIT PARTITION – ALTER TABLE ... MOVE PARTITION – ALTER TABLE ... MODIFY PARTITION ... ADD SUBPARTITION – ALTER TABLE ... MODIFY PARTITION ... COALESCE SUBPARTITION ■ CREATE INDEX ■ ALTER INDEX ... REBUILD ■ ALTER INDEX ... REBUILD [SUB]PARTITION ■ ALTER INDEX ... SPLIT PARTITION
- 478. logging_clause 8-38 Oracle Database SQL Reference For objects other than LOBs, if you omit this clause, then the logging attribute of the object defaults to the logging attribute of the tablespace in which it resides. For LOBs, if you omit this clause: ■ If you specify CACHE, then LOGGING is used (because you cannot have CACHE NOLOGGING). ■ If you specify NOCACHE or CACHE READS, then the logging attribute defaults to the logging attribute of the tablespace in which it resides. NOLOGGING does not apply to LOBs that are stored inline with row data. That is, if you specify NOLOGGING for LOBs with values less than 4000 bytes and you have not disabled STORAGE IN ROW, then Oracle ignores the NOLOGGING specification and treats the LOB data the same as other table data. See Also: Oracle Database Concepts and Oracle Database Administrator's Guide for more information about logging and parallel DML
- 479. parallel_clause Common SQL DDL Clauses 8-39 parallel_clause Purpose The parallel_clause lets you parallelize the creation of a database object and set the default degree of parallelism for subsequent queries of and DML operations on the object. You can specify the parallel_clause in the following statements: ■ CREATE TABLE: to set parallelism for the table (see CREATE TABLE on page 16-6). ■ ALTER TABLE (see ALTER TABLE on page 12-2): – To change parallelism for the table – To parallelize the operations of adding, coalescing, exchanging, merging, splitting, truncating, dropping, or moving a table partition ■ CREATE CLUSTER and ALTER CLUSTER: to set or alter parallelism for a cluster (see CREATE CLUSTER on page 14-2 and ALTER CLUSTER on page 10-5). ■ CREATE INDEX: to set parallelism for the index (see CREATE INDEX on page 14-58). ■ ALTER INDEX (see ALTER INDEX on page 10-64): – To change parallelism for the index – To parallelize the rebuilding of the index or the splitting of an index partition ■ CREATE MATERIALIZED VIEW: to set parallelism for the materialized view (see CREATE MATERIALIZED VIEW on page 15-4). ■ ALTER MATERIALIZED VIEW (see ALTER MATERIALIZED VIEW on page 11-2): – To change parallelism for the materialized view – To parallelize the operations of adding, coalescing, exchanging, merging, splitting, truncating, dropping, or moving a materialized view partition – To parallelize the operations of adding or moving materialized view subpartitions ■ CREATE MATERIALIZED VIEW LOG: to set parallelism for the materialized view log (see CREATE MATERIALIZED VIEW LOG on page 15-25). ■ ALTER MATERIALIZED VIEW LOG (see ALTER MATERIALIZED VIEW LOG on page 11-15): – To change parallelism for the materialized view log – To parallelize the operations of adding, coalescing, exchanging, merging, splitting, truncating, dropping, or moving a materialized view log partition ■ ALTER DATABASE ... RECOVER: to recover the database (see ALTER DATABASE on page 10-9). ■ ALTER DATABASE ... standby_database_clauses: to parallelize operations on the standby database (see ALTER DATABASE on page 10-9).
- 480. parallel_clause 8-40 Oracle Database SQL Reference Syntax parallel_clause::= Semantics This section describes the semantics of the parallel_clause. For additional information, refer to the SQL statement in which you set or reset parallelism for a particular database object or operation. NOPARALLEL Specify NOPARALLEL for serial execution. This is the default. PARALLEL Specify PARALLEL if you want Oracle to select a degree of parallelism equal to the number of CPUs available on all participating instances times the value of the PARALLEL_THREADS_PER_CPU initialization parameter. PARALLEL integer Specification of integer indicates the degree of parallelism, which is the number of parallel threads used in the parallel operation. Each parallel thread may use one or two parallel execution servers. Normally Oracle calculates the optimum degree of parallelism, so it is not necessary for you to specify integer. Notes on the parallel_clause The following notes apply to the parallel_clause: ■ Parallelism is disabled for DML operations on tables on which you have defined a trigger or referential integrity constraint. ■ When you specify the parallel_clause during creation of a table, if the table contains any columns of LOB or user-defined object type, then subsequent INSERT, UPDATE, DELETE or MERGE operations that modify the LOB or object type column are executed serially without notification. Subsequent queries, however, will be executed in parallel. ■ A parallel hint overrides the effect of the parallel_clause. ■ DML statements and CREATE TABLE ... AS SELECT statements that reference remote objects can run in parallel. However, the remote object must really be on a remote database. The reference cannot loop back to an object on the local database, for example, by way of a synonym on the remote database pointing back to an object on the local database. ■ DML operations on tables with LOB columns can be parallelized. However, intrapartition parallelism is not supported. Note: The syntax of the parallel_clause supersedes syntax appearing in earlier releases of Oracle. Superseded syntax is still supported for backward compatibility but may result in slightly different behavior from that documented. See Also: Oracle Database Performance Tuning Guide, Oracle Database Concepts, and Oracle Database Data Warehousing Guide for more information on parallelized operations, and "PARALLEL Example" on page 16-51 NOPARALLEL PARALLEL integer
- 481. physical_attributes_clause Common SQL DDL Clauses 8-41 physical_attributes_clause Purpose The physical_attributes_clause lets you specify the value of the PCTFREE, PCTUSED, and INITRANS parameters and the storage characteristics of a table, cluster, index, or materialized view. You can specify the physical_attributes_clause in the following statements: ■ CREATE CLUSTER and ALTER CLUSTER: to set or change the physical attributes of the cluster and all tables in the cluster (see CREATE CLUSTER on page 14-2 and ALTER CLUSTER on page 10-5). ■ CREATE TABLE: to set the physical attributes of the table, a table partition, the OIDINDEX of an object table, or the overflow segment of an index-organized table (see CREATE TABLE on page 16-6). ■ ALTER TABLE: to change the physical attributes of the table, the default physical attributes of future table partitions, or the physical attributes of existing table partitions (see ALTER TABLE on page 12-2). The following restrictions apply: – You cannot specify physical attributes for a temporary table. – You cannot specify physical attributes for a clustered table. Tables in a cluster inherit the physical attributes of the cluster. ■ CREATE INDEX: to set the physical attributes of an index or index partition (see CREATE INDEX on page 14-58). ■ ALTER INDEX: to change the physical attributes of the index, the default physical attributes of future index partitions, or the physical attributes of existing index partitions (see ALTER INDEX on page 10-64). ■ CREATE MATERIALIZED VIEW: to set the physical attributes of the materialized view, one of its partitions, or the index Oracle Database generates to maintain the materialized view (see CREATE MATERIALIZED VIEW on page 15-4). ■ ALTER MATERIALIZED VIEW: to change the physical attributes of the materialized view, the default physical attributes of future partitions, the physical attributes of an existing partition, or the index Oracle creates to maintain the materialized view (see ALTER MATERIALIZED VIEW on page 11-2). ■ CREATE MATERIALIZED VIEW LOG and ALTER MATERIALIZED VIEW LOG: to set or change the physical attributes of the materialized view log (see CREATE MATERIALIZED VIEW LOG on page 15-25 and ALTER MATERIALIZED VIEW LOG on page 11-15). Syntax physical_attributes_clause::= PCTFREE integer PCTUSED integer INITRANS integer storage_clause
- 482. physical_attributes_clause 8-42 Oracle Database SQL Reference (storage_clause::= on page 8-47) Semantics This section describes the parameters of the physical_attributes_clause. For additional information, refer to the SQL statement in which you set or reset these parameters for a particular database object. PCTFREE integer Specify a whole number representing the percentage of space in each data block of the database object reserved for future updates to rows of the object. The value of PCTFREE must be a value from 0 to 99. A value of 0 means that the entire block can be filled by inserts of new rows. The default value is 10. This value reserves 10% of each block for updates to existing rows and allows inserts of new rows to fill a maximum of 90% of each block. PCTFREE has the same function in the statements that create and alter tables, partitions, clusters, indexes, materialized views, and materialized view logs. The combination of PCTFREE and PCTUSED determines whether new rows will be inserted into existing data blocks or into new blocks. Restriction on the PCTFREE Clause When altering an index, you can specify this parameter only in the modify_index_default_attrs clause and the split_ partition_clause. PCTUSED integer Specify a whole number representing the minimum percentage of used space that Oracle maintains for each data block of the database object. A block becomes a candidate for row insertion when its used space falls below PCTUSED. PCTUSED is specified as a positive integer from 0 to 99 and defaults to 40. PCTUSED has the same function in the statements that create and alter tables, partitions, clusters, materialized views, and materialized view logs. PCTUSED is not a valid table storage characteristic for an index-organized table. The sum of PCTFREE and PCTUSED must be equal to or less than 100. You can use PCTFREE and PCTUSED together to utilize space within a database object more efficiently. Restrictions on the PCTUSED Clause You cannot specify this parameter for an index or for the index segment of an index-organized table. INITRANS integer Specify the initial number of concurrent transaction entries allocated within each data block allocated to the database object. This value can range from 1 to 255 and defaults to 1, with the following exceptions: ■ The default INITRANS value for a cluster is 2 or the default INITRANS value of the tablespace in which the cluster resides, whichever is greater. ■ The default value for an index is 2. In general, you should not change the INITRANS value from its default. See Also: Oracle Database Performance Tuning Guide for information on the performance effects of different values of PCTUSED and PCTFREE
- 483. physical_attributes_clause Common SQL DDL Clauses 8-43 Each transaction that updates a block requires a transaction entry in the block. The size of a transaction entry depends on your operating system. This parameter ensures that a minimum number of concurrent transactions can update the block and helps avoid the overhead of dynamically allocating a transaction entry. The INITRANS parameter serves the same purpose in the statements that create and alter tables, partitions, clusters, indexes, materialized views, and materialized view logs. MAXTRANS Parameter In earlier releases, the MAXTRANS parameter determined the maximum number of concurrent update transactions allowed for each data block in the segment. This parameter has been deprecated. Oracle now automatically allows up to 255 concurrent update transactions for any data block, depending on the available space in the block. Existing objects for which a value of MAXTRANS has already been set retain that setting. However, if you attempt to change the value for MAXTRANS, Oracle ignores the new specification and substitutes the value 255 without returning an error. storage_clause The storage_clause lets you specify storage characteristics for the table, object table OIDINDEX, partition, LOB data segment, LOB index segment, or index-organized table overflow data segment. This clause has performance ramifications for large tables. Storage should be allocated to minimize dynamic allocation of additional space. Please refer to the storage_clause on page 8-46 for more information.
- 484. size_clause 8-44 Oracle Database SQL Reference size_clause Purpose The size_clause lets you specify a number of bytes, kilobytes (K), megabytes (M), gigabytes (G), terabytes (T), petabytes (P), or exabytes (E) in any statement that lets you establish amounts of disk or memory space. Syntax size_clause::= Semantics Use the size_clause to specify a number or multiple of bytes. If you do not specify any of the multiple abbreviations, the integer is interpreted as bytes. Note: Not all multiples of bytes are appropriate in all cases, and context-sensitive limitations may apply. In the latter case, Oracle issues an error message. integer K M G T P E
- 485. storage_clause Common SQL DDL Clauses 8-45 storage_clause Purpose The storage_clause lets you specify how Oracle Database should store a database object. Storage parameters affect both how long it takes to access data stored in the database and how efficiently space in the database is used. When you create a cluster, index, materialized view, materialized view log, rollback segment, table, or partition, you can specify values for the storage parameters for the segments allocated to these objects. If you omit any storage parameter, then Oracle uses the value of that parameter specified for the tablespace in which the object resides. When you alter a cluster, index, materialized view, materialized view log, rollback segment, table, or partition, you can change the values of storage parameters. The new values affect only future extent allocations. The storage_clause is part of the physical_attributes_clause, so you can specify this clause in any of the statements where you can specify the physical attributes clause (see physical_attributes_clause on page 8-42). In addition, you can specify the storage_clause in the following statements: ■ CREATE CLUSTER and ALTER CLUSTER: to set or change the storage characteristics of the cluster and all tables in the cluster (see CREATE CLUSTER on page 14-2 and ALTER CLUSTER on page 10-5). ■ CREATE INDEX and ALTER INDEX: to set or change the storage characteristics of an index or index partition (see CREATE INDEX on page 14-58 and ALTER INDEX on page 10-64). ■ CREATE MATERIALIZED VIEW and ALTER MATERIALIZED VIEW: to set or change the storage characteristics of a materialized view, one of its partitions, or the index Oracle generates to maintain the materialized view (see CREATE MATERIALIZED VIEW on page 15-4 and ALTER MATERIALIZED VIEW on page 11-2). ■ CREATE MATERIALIZED VIEW LOG and ALTER MATERIALIZED VIEW LOG: to set or change the storage characteristics of the materialized view log (see CREATE MATERIALIZED VIEW LOG on page 15-25 and ALTER MATERIALIZED VIEW LOG on page 11-15). ■ CREATE ROLLBACK SEGMENT and ALTER ROLLBACK SEGMENT: to set or change the storage characteristics of a rollback segment (see CREATE ROLLBACK SEGMENT on page 15-66 and ALTER ROLLBACK SEGMENT on page 11-40). ■ CREATE TABLE and ALTER TABLE: to set the storage characteristics of a LOB data segment of the table or one of its partitions or subpartitions (see CREATE TABLE on page 16-6 and ALTER TABLE on page 12-2). See Also: Oracle Database Performance Tuning Guide for a discussion of the effects of the storage parameters Note: The specification of storage parameters for objects in locally managed tablespaces is supported for backward compatibility. If you are using locally managed tablespaces, you can omit these storage parameter when creating objects in those tablespaces.
- 486. storage_clause 8-46 Oracle Database SQL Reference ■ CREATE TABLESPACE and ALTER TABLESPACE: to set or change the default storage characteristics for objects created in the tablespace (see CREATE TABLESPACE on page 16-61 and ALTER TABLESPACE on page 12-79). ■ constraint: to specify storage for the index (and its partitions, if it is a partitioned index) used to enforce the constraint (see constraint on page 8-4). Prerequisites To change the value of a STORAGE parameter, you must have the privileges necessary to use the appropriate CREATE or ALTER statement. Syntax storage_clause::= (size_clause::= on page 8-45 Semantics This section describes the parameters of the storage_clause. For additional information, refer to the SQL statement in which you set or reset these parameters for a particular database object. Note: The storage_clause is interpreted differently for locally managed tablespaces. At creation, Oracle ignores MAXEXTENTS and uses the remaining parameter values to calculate the initial size of the segment. For more information, see CREATE TABLESPACE on page 16-61. See Also: "Specifying Table Storage Attributes: Example" on page 8-51 STORAGE ( INITIAL size_clause NEXT size_clause MINEXTENTS integer MAXEXTENTS integer UNLIMITED PCTINCREASE integer FREELISTS integer FREELIST GROUPS integer OPTIMAL size_clause NULL BUFFER_POOL KEEP RECYCLE DEFAULT )
- 487. storage_clause Common SQL DDL Clauses 8-47 INITIAL Specify the size of the first extent of the object. Oracle allocates space for this extent when you create the schema object. Please refer to size_clause on page 8-45 for information on that clause. The default value is the size of 5 data blocks. In tablespaces with manual segment-space management, the minimum value is the size of 2 data blocks plus one data block for each free list group you specify. In tablespaces with automatic segment-space management, the minimum value is 5 data blocks. The maximum value depends on your operating system. Please refer to FREELIST GROUPS on page 8-50 for information on freelist groups for more information. In dictionary-managed tablespaces, if MINIMUM EXTENT was specified for the tablespace when it was created, then Oracle rounds the value of INITIAL up to the specified MINIMUM EXTENT size if necessary. If MINIMUM EXTENT was not specified, then Oracle rounds the INITIAL extent size for segments created in that tablespace up to the minimum value (see preceding paragraph), or to multiples of 5 blocks if the requested size is greater than 5 blocks. In locally managed tablespaces, Oracle uses the value of INITIAL in conjunction with the size of extents specified for the tablespace to determine the first extent of the object. For example, in a uniform locally managed tablespace with 5M extents, if you specify an INITIAL value of 1M, then Oracle creates five 1M extents. Restriction on INITIAL You cannot specify INITIAL in an ALTER statement. NEXT Specify in bytes the size of the next extent to be allocated to the object. Please refer to size_clause on page 8-45 for information on that clause. The default value is the size of 5 data blocks. The minimum value is the size of 1 data block. The maximum value depends on your operating system. Oracle rounds values up to the next multiple of the data block size for values less than 5 data blocks. For values greater than 5 data blocks, Oracle rounds up to a value that minimizes fragmentation, as described in Oracle Database Administrator's Guide. If you change the value of the NEXT parameter (that is, if you specify it in an ALTER statement), then the next allocated extent will have the specified size, regardless of the size of the most recently allocated extent and the value of the PCTINCREASE parameter. PCTINCREASE Specify the percent by which the third and subsequent extents grow over the preceding extent. The default value is 50, meaning that each subsequent extent is 50% larger than the preceding extent. The minimum value is 0, meaning all extents after the first are the same size. The maximum value depends on your operating system. Oracle rounds the calculated size of each new extent to the nearest multiple of the data block size. If you change the value of the PCTINCREASE parameter (that is, if you specify it in an ALTER statement), then Oracle calculates the size of the next extent using this new value and the size of the most recently allocated extent. See Also: Oracle Database Administrator's Guide for information on how Oracle minimizes fragmentation
- 488. storage_clause 8-48 Oracle Database SQL Reference Restriction on PCTINCREASE You cannot specify PCTINCREASE for rollback segments. Rollback segments always have a PCTINCREASE value of 0. MINEXTENTS Specify the total number of extents to allocate when the object is created. This parameter lets you allocate a large amount of space when you create an object, even if the space available is not contiguous. The default and minimum value is 1, meaning that Oracle allocates only the initial extent, except for rollback segments, for which the default and minimum value is 2. The maximum value depends on your operating system. If the MINEXTENTS value is greater than 1, then Oracle calculates the size of subsequent extents based on the values of the INITIAL, NEXT, and PCTINCREASE storage parameters. When changing the value of MINEXTENTS (that is, in an ALTER statement), you can reduce the value from its current value, but you cannot increase it. Resetting MINEXTENTS to a smaller value might be useful, for example, before a TRUNCATE ... DROP STORAGE statement, if you want to ensure that the segment will maintain a minimum number of extents after the TRUNCATE operation. Restriction on MINEXTENTS You cannot change the value of MINEXTENTS for an object that resides in a locally managed tablespace. MAXEXTENTS Specify the total number of extents, including the first, that Oracle can allocate for the object. The minimum value is 1 except for rollback segments, which always have a minimum of 2. The default value depends on your data block size. Restriction on MAXEXTENTS You cannot change the value of MAXEXTENTS for an object that resides in a locally managed tablespace. UNLIMITED Specify UNLIMITED if you want extents to be allocated automatically as needed. Oracle recommends this setting as a way to minimize fragmentation. Do not use this clause for rollback segments. Doing so allows the possibility that long-running rogue DML transactions will continue to create new extents until a disk is full. Suggestion: If you want to keep all extents the same size, you can prevent the SMON background process from coalescing extents by setting the value of PCTINCREASE to 0. In general, Oracle recommends a setting of 0 as a way to minimize fragmentation and avoid the possibility of very large temporary segments during processing. Caution: A rollback segment that you create without specifying the storage_clause has the same storage parameters as the tablespace in which the rollback segment is created. Thus, if you create a tablespace with MAXEXTENTS UNLIMITED, then the rollback segment will have this same default.
- 489. storage_clause Common SQL DDL Clauses 8-49 FREELIST GROUPS Specify the number of groups of free lists for the database object you are creating. The default and minimum value for this parameter is 1. Oracle uses the instance number of Real Application Clusters instances to map each instance to one free list group. Each free list group uses one database block. Therefore: ■ If you do not specify a large enough value for INITIAL to cover the minimum value plus one data block for each free list group, then Oracle increases the value of INITIAL the necessary amount. ■ If you are creating an object in a uniform locally managed tablespace, and the extent size is not large enough to accommodate the number of freelist groups, then the create operation will fail. Oracle ignores a setting of FREELIST GROUPS if the tablespace in which the object resides is in automatic segment-space management mode. If you are running your database in this mode, please refer to the FREEPOOLS parameter of the LOB_ storage_clause on page 16-32. Restriction on FREELIST GROUPS You can specify the FREELIST GROUPS parameter only in CREATE TABLE, CREATE CLUSTER, CREATE MATERIALIZED VIEW, CREATE MATERIALIZED VIEW LOG, and CREATE INDEX statements. FREELISTS For objects other than tablespaces and rollback segments, specify the number of free lists for each of the free list groups for the table, partition, cluster, or index. The default and minimum value for this parameter is 1, meaning that each free list group contains one free list. The maximum value of this parameter depends on the data block size. If you specify a FREELISTS value that is too large, then Oracle returns an error indicating the maximum value. Oracle ignores a setting of FREELISTS if the tablespace in which the object resides is in automatic segment-space management mode. If you are running your database in this mode, please refer to the FREEPOOLS parameter of the LOB_storage_clause on page 16-32. Restriction on FREELISTS You can specify FREELISTS in the storage_clause of any statement except when creating or altering a tablespace or rollback segment. BUFFER_POOL The BUFFER_POOL clause lets you specify a default buffer pool or cache for a schema object. All blocks for the object are stored in the specified cache. ■ If you define a buffer pool for a partitioned table or index, then the partitions inherit the buffer pool from the table or index definition unless overridden by a partition-level definition. ■ For an index-organized table, you can specify a buffer pool separately for the index segment and the overflow segment. Restrictions on the BUFFER_POOL Parameter BUFFER_POOL is subject to the following restrictions: See Also: Oracle Database Oracle Clusterware and Oracle Real Application Clusters Administration and Deployment Guide for information on associating instances with free list groups
- 490. storage_clause 8-50 Oracle Database SQL Reference ■ You cannot specify this clause for a cluster table. However, you can specify it for a cluster. ■ You cannot specify this clause for a tablespace or a rollback segment. KEEP Specify KEEP to put blocks from the segment into the KEEP buffer pool. Maintaining an appropriately sized KEEP buffer pool lets Oracle retain the schema object in memory to avoid I/O operations. KEEP takes precedence over any NOCACHE clause you specify for a table, cluster, materialized view, or materialized view log. RECYCLE Specify RECYCLE to put blocks from the segment into the RECYCLE pool. An appropriately sized RECYCLE pool reduces the number of objects whose default pool is the RECYCLE pool from taking up unnecessary cache space. DEFAULT Specify DEFAULT to indicate the default buffer pool. This is the default for objects not assigned to KEEP or RECYCLE. OPTIMAL The OPTIMAL keyword is relevant only to rollback segments. It specifies an optimal size in bytes for a rollback segment. Please refer to size_clause on page 8-45 for information on that clause. Oracle tries to maintain this size for the rollback segment by dynamically deallocating extents when their data is no longer needed for active transactions. Oracle deallocates as many extents as possible without reducing the total size of the rollback segment below the OPTIMAL value. The value of OPTIMAL cannot be less than the space initially allocated by the MINEXTENTS, INITIAL, NEXT, and PCTINCREASE parameters. The maximum value depends on your operating system. Oracle rounds values up to the next multiple of the data block size. NULL Specify NULL for no optimal size for the rollback segment, meaning that Oracle never deallocates the extents of the rollback segment. This is the default behavior. Example Specifying Table Storage Attributes: Example The following statement creates a table and provides storage parameter values: CREATE TABLE divisions (div_no NUMBER(2), div_name VARCHAR2(14), location VARCHAR2(13) ) STORAGE ( INITIAL 100K NEXT 50K MINEXTENTS 1 MAXEXTENTS 50 PCTINCREASE 5); Oracle allocates space for the table based on the STORAGE parameter values as follows: ■ The MINEXTENTS value is 1, so Oracle allocates 1 extent for the table upon creation. ■ The INITIAL value is 100K, so the size of the first extent is 100 kilobytes. ■ If the table data grows to exceed the first extent, then Oracle allocates a second extent. The NEXT value is 50K, so the size of the second extent will be 50 kilobytes. See Also: Oracle Database Performance Tuning Guide for more information about using multiple buffer pools
- 491. storage_clause Common SQL DDL Clauses 8-51 ■ If the table data subsequently grows to exceed the first two extents, then Oracle allocates a third extent. The PCTINCREASE value is 5, so the calculated size of the third extent is 5% larger than the second extent, or 52.5 kilobytes. If the data block size is 2 kilobytes, then Oracle rounds this value to 52 kilobytes. If the table data continues to grow, then Oracle allocates more extents, each 5% larger than the previous one. ■ The MAXEXTENTS value is 50, so Oracle can allocate as many as 50 extents for the table.
- 492. storage_clause 8-52 Oracle Database SQL Reference
- 493. SQL Queries and Subqueries 9-1 9 SQL Queries and Subqueries This chapter describes SQL queries and subqueries. This chapter contains these sections: ■ About Queries and Subqueries ■ Creating Simple Queries ■ Hierarchical Queries ■ The UNION [ALL], INTERSECT, MINUS Operators ■ Sorting Query Results ■ Joins ■ Using Subqueries ■ Unnesting of Nested Subqueries ■ Selecting from the DUAL Table ■ Distributed Queries About Queries and Subqueries A query is an operation that retrieves data from one or more tables or views. In this reference, a top-level SELECT statement is called a query, and a query nested within another SQL statement is called a subquery. This section describes some types of queries and subqueries and how to use them. The top level of the syntax is shown in this chapter. Please refer to SELECT on page 19-4 for the full syntax of all the clauses and the semantics of this statement. select::= subquery for_update_clause ;
- 494. Creating Simple Queries 9-2 Oracle Database SQL Reference subquery::= Creating Simple Queries The list of expressions that appears after the SELECT keyword and before the FROM clause is called the select list. Within the select list, you specify one or more columns in the set of rows you want Oracle Database to return from one or more tables, views, or materialized views. The number of columns, as well as their datatype and length, are determined by the elements of the select list. If two or more tables have some column names in common, then you must qualify column names with names of tables. Otherwise, fully qualified column names are optional. However, it is always a good idea to qualify table and column references explicitly. Oracle often does less work with fully qualified table and column names. You can use a column alias, c_alias, to label the immediately preceding expression in the select list so that the column is displayed with a new heading. The alias effectively renames the select list item for the duration of the query. The alias can be used in the ORDER BY clause, but not other clauses in the query. You can use comments in a SELECT statement to pass instructions, or hints, to the Oracle Database optimizer. The optimizer uses hints to choose an execution plan for the statement. Please refer to "Using Hints" on page 2-71 and Oracle Database Performance Tuning Guide for more information on hints. Hierarchical Queries If a table contains hierarchical data, then you can select rows in a hierarchical order using the hierarchical query clause: subquery_factoring_clause SELECT hint DISTINCT UNIQUE ALL select_list FROM table_reference , join_clause ( join_clause ) where_clause hierarchical_query_clause group_by_clause HAVING condition model_clause UNION ALL INTERSECT MINUS ( subquery ) order_by_clause
- 495. Hierarchical Queries SQL Queries and Subqueries 9-3 hierarchical_query_clause::= START WITH specifies the root row(s) of the hierarchy. CONNECT BY specifies the relationship between parent rows and child rows of the hierarchy. ■ The NOCYCLE parameter instructs Oracle Database to return rows from a query even if a CONNECT BY LOOP exists in the data. Use this parameter along with the CONNECT_BY_ISCYCLE pseudocolumn to see which rows contain the loop. Please refer to CONNECT_BY_ISCYCLE Pseudocolumn on page 3-1 for more information. ■ In a hierarchical query, one expression in condition must be qualified with the PRIOR operator to refer to the parent row. For example, ... PRIOR expr = expr or ... expr = PRIOR expr If the CONNECT BY condition is compound, then only one condition requires the PRIOR operator, although you can have multiple PRIOR conditions. For example: CONNECT BY last_name != 'King' AND PRIOR employee_id = manager_id ... CONNECT BY PRIOR employee_id = manager_id and PRIOR account_mgr_id = customer_id ... PRIOR is a unary operator and has the same precedence as the unary + and - arithmetic operators. It evaluates the immediately following expression for the parent row of the current row in a hierarchical query. PRIOR is most commonly used when comparing column values with the equality operator. (The PRIOR keyword can be on either side of the operator.) PRIOR causes Oracle to use the value of the parent row in the column. Operators other than the equal sign (=) are theoretically possible in CONNECT BY clauses. However, the conditions created by these other operators can result in an infinite loop through the possible combinations. In this case Oracle detects the loop at run time and returns an error. Both the CONNECT BY condition and the PRIOR expression can take the form of an uncorrelated subquery. However, the PRIOR expression cannot refer to a sequence. That is, CURRVAL and NEXTVAL are not valid PRIOR expressions. You can further refine a hierarchical query by using the CONNECT_BY_ROOT operator to qualify a column in the select list. This operator extends the functionality of the CONNECT BY [PRIOR] condition of hierarchical queries by returning not only the immediate parent row but all ancestor rows in the hierarchy. Oracle processes hierarchical queries as follows: ■ A join, if present, is evaluated first, whether the join is specified in the FROM clause or with WHERE clause predicates. ■ The CONNECT BY condition is evaluated. See Also: CONNECT_BY_ROOT on page 4-5 for more information about this operator and "Hierarchical Query Examples" on page 9-5 START WITH condition CONNECT BY NOCYCLE condition
- 496. Hierarchical Queries 9-4 Oracle Database SQL Reference ■ Any remaining WHERE clause predicates are evaluated. Oracle then uses the information from these evaluations to form the hierarchy using the following steps: 1. Oracle selects the root row(s) of the hierarchy--those rows that satisfy the START WITH condition. 2. Oracle selects the child rows of each root row. Each child row must satisfy the condition of the CONNECT BY condition with respect to one of the root rows. 3. Oracle selects successive generations of child rows. Oracle first selects the children of the rows returned in step 2, and then the children of those children, and so on. Oracle always selects children by evaluating the CONNECT BY condition with respect to a current parent row. 4. If the query contains a WHERE clause without a join, then Oracle eliminates all rows from the hierarchy that do not satisfy the condition of the WHERE clause. Oracle evaluates this condition for each row individually, rather than removing all the children of a row that does not satisfy the condition. 5. Oracle returns the rows in the order shown in Figure 9–1. In the diagram, children appear below their parents. For an explanation of hierarchical trees, see Figure 3–1, "Hierarchical Tree" on page 3-3. Figure 9–1 Hierarchical Queries To find the children of a parent row, Oracle evaluates the PRIOR expression of the CONNECT BY condition for the parent row and the other expression for each row in the table. Rows for which the condition is true are the children of the parent. The CONNECT BY condition can contain other conditions to further filter the rows selected by the query. The CONNECT BY condition cannot contain a subquery. If the CONNECT BY condition results in a loop in the hierarchy, then Oracle returns an error. A loop occurs if one row is both the parent (or grandparent or direct ancestor) and a child (or a grandchild or a direct descendent) of another row. Note: In a hierarchical query, do not specify either ORDER BY or GROUP BY, as they will destroy the hierarchical order of the CONNECT BY results. If you want to order rows of siblings of the same parent, then use the ORDER SIBLINGS BY clause. See order_by_clause on page 19-28. 1 7 8 ROOT 2 9 3 4 10 12 1165
- 497. Hierarchical Queries SQL Queries and Subqueries 9-5 Hierarchical Query Examples CONNECT BY Example The following hierarchical query uses the CONNECT BY clause to define the relationship between employees and managers: SELECT employee_id, last_name, manager_id FROM employees CONNECT BY PRIOR employee_id = manager_id; EMPLOYEE_ID LAST_NAME MANAGER_ID ----------- ------------------------- ---------- 101 Kochhar 100 108 Greenberg 101 109 Faviet 108 110 Chen 108 111 Sciarra 108 112 Urman 108 113 Popp 108 200 Whalen 101 ... LEVEL Example The next example is similar to the preceding example, but uses the LEVEL pseudocolumn to show parent and child rows: SELECT employee_id, last_name, manager_id, LEVEL FROM employees CONNECT BY PRIOR employee_id = manager_id; EMPLOYEE_ID LAST_NAME MANAGER_ID LEVEL ----------- ------------------------- ---------- ---------- 101 Kochhar 100 1 108 Greenberg 101 2 109 Faviet 108 3 110 Chen 108 3 111 Sciarra 108 3 112 Urman 108 3 113 Popp 108 3 ... START WITH Examples The next example adds a START WITH clause to specify a root row for the hierarchy and an ORDER BY clause using the SIBLINGS keyword to preserve ordering within the hierarchy: SELECT last_name, employee_id, manager_id, LEVEL FROM employees START WITH employee_id = 100 CONNECT BY PRIOR employee_id = manager_id ORDER SIBLINGS BY last_name; LAST_NAME EMPLOYEE_ID MANAGER_ID LEVEL ------------------------- ----------- ---------- ---------- King 100 1 Cambrault 148 100 2 Bates 172 148 3 Bloom 169 148 3 Fox 170 148 3 Kumar 173 148 3 Ozer 168 148 3 Smith 171 148 3 De Haan 102 100 2
- 498. Hierarchical Queries 9-6 Oracle Database SQL Reference Hunold 103 102 3 Austin 105 103 4 Ernst 104 103 4 Lorentz 107 103 4 Pataballa 106 103 4 Errazuriz 147 100 2 Ande 166 147 3 Banda 167 147 3 ... In the hr.employees table, the employee Steven King is the head of the company and has no manager. Among his employees is John Russell, who is the manager of department 80. If we update the employees table to set Russell as King's manager, we will create a loop in the data: UPDATE employees SET manager_id = 145 WHERE employee_id = 100; SELECT last_name "Employee", LEVEL, SYS_CONNECT_BY_PATH(last_name, '/') "Path" FROM employees WHERE level <= 3 AND department_id = 80 START WITH last_name = 'King' CONNECT BY PRIOR employee_id = manager_id AND LEVEL <= 4; 2 3 4 5 6 7 ERROR: ORA-01436: CONNECT BY loop in user data The NOCYCLE parameter in the CONNECT BY condition causes Oracle to return the rows in spite of the loop. The CONNECT_BY_ISCYCLE pseudocolumn shows you which rows contain the cycle: SELECT last_name "Employee", CONNECT_BY_ISCYCLE "Cycle", LEVEL, SYS_CONNECT_BY_PATH(last_name, '/') "Path" FROM employees WHERE level <= 3 AND department_id = 80 START WITH last_name = 'King' CONNECT BY NOCYCLE PRIOR employee_id = manager_id AND LEVEL <= 4; Employee Cycle LEVEL Path ------------------------- ------ ------ ------------------------- Russell 1 2 /King/Russell Tucker 0 3 /King/Russell/Tucker Bernstein 0 3 /King/Russell/Bernstein Hall 0 3 /King/Russell/Hall Olsen 0 3 /King/Russell/Olsen Cambrault 0 3 /King/Russell/Cambrault Tuvault 0 3 /King/Russell/Tuvault Partners 0 2 /King/Partners King 0 3 /King/Partners/King Sully 0 3 /King/Partners/Sully McEwen 0 3 /King/Partners/McEwen ... CONNECT_BY_ROOT Examples The following example returns the last name of each employee in department 110, each manager above that employee in the hierarchy, the number of levels between manager and employee, and the path between the two: SELECT last_name "Employee", CONNECT_BY_ROOT last_name "Manager", LEVEL-1 "Pathlen", SYS_CONNECT_BY_PATH(last_name, '/') "Path" FROM employees WHERE LEVEL > 1 and department_id = 110
- 499. The UNION [ALL], INTERSECT, MINUS Operators SQL Queries and Subqueries 9-7 CONNECT BY PRIOR employee_id = manager_id; Employee Manager Pathlen Path --------------- ------------ ---------- ----------------------------------- Higgins Kochhar 1 /Kochhar/Higgins Gietz Kochhar 2 /Kochhar/Higgins/Gietz Gietz Higgins 1 /Higgins/Gietz Higgins King 2 /King/Kochhar/Higgins Gietz King 3 /King/Kochhar/Higgins/Gietz The following example uses a GROUP BY clause to return the total salary of each employee in department 110 and all employees below that employee in the hierarchy: SELECT name, SUM(salary) "Total_Salary" FROM ( SELECT CONNECT_BY_ROOT last_name as name, Salary FROM employees WHERE department_id = 110 CONNECT BY PRIOR employee_id = manager_id) GROUP BY name; NAME Total_Salary ------------------------- ------------ Gietz 8300 Higgins 20300 King 20300 Kochhar 20300 The UNION [ALL], INTERSECT, MINUS Operators You can combine multiple queries using the set operators UNION, UNION ALL, INTERSECT, and MINUS. All set operators have equal precedence. If a SQL statement contains multiple set operators, then Oracle Database evaluates them from the left to right unless parentheses explicitly specify another order. The corresponding expressions in the select lists of the component queries of a compound query must match in number and must be in the same datatype group (such as numeric or character). If component queries select character data, then the datatype of the return values are determined as follows: ■ If both queries select values of datatype CHAR of equal length, then the returned values have datatype CHAR of that length. If the queries select values of CHAR with different lengths, then the returned value is VARCHAR2 with the length of the larger CHAR value. ■ If either or both of the queries select values of datatype VARCHAR2, then the returned values have datatype VARCHAR2. See Also: ■ LEVEL Pseudocolumn on page 3-2 and CONNECT_BY_ISCYCLE Pseudocolumn on page 3-1 for a discussion of how these pseudocolumns operate in a hierarchical query ■ SYS_CONNECT_BY_PATH on page 5-176 for information on retrieving the path of column values from root to node ■ order_by_clause on page 19-28 for more information on the SIBLINGS keyword of ORDER BY clauses
- 500. The UNION [ALL], INTERSECT, MINUS Operators 9-8 Oracle Database SQL Reference If component queries select numeric data, then the datatype of the return values is determined by numeric precedence: ■ If any query selects values of type BINARY_DOUBLE, then the returned values have datatype BINARY_DOUBLE. ■ If no query selects values of type BINARY_DOUBLE but any query selects values of type BINARY_FLOAT, then the returned values have datatype BINARY_FLOAT. ■ If all queries select values of type NUMBER, then the returned values have datatype NUMBER. In queries using set operators, Oracle does not perform implicit conversion across datatype groups. Therefore, if the corresponding expressions of component queries resolve to both character data and numeric data, Oracle returns an error. Examples The following query is valid: SELECT 3 FROM DUAL INTERSECT SELECT 3f FROM DUAL; This is implicitly converted to the following compound query: SELECT TO_BINARY_FLOAT(3) FROM DUAL INTERSECT SELECT 3f FROM DUAL; The following query returns an error: SELECT '3' FROM DUAL INTERSECT SELECT 3f FROM DUAL; Restrictions on the Set Operators The set operators are subject to the following restrictions: ■ The set operators are not valid on columns of type BLOB, CLOB, BFILE, VARRAY, or nested table. ■ The UNION, INTERSECT, and MINUS operators are not valid on LONG columns. ■ If the select list preceding the set operator contains an expression, then you must provide a column alias for the expression in order to refer to it in the order_by_ clause. ■ You cannot also specify the for_update_clause with the set operators. ■ You cannot specify the order_by_clause in the subquery of these operators. ■ You cannot use these operators in SELECT statements containing TABLE collection expressions. See Also: Table 2–10, " Implicit Type Conversion Matrix" on page 2-41 for more information on implicit conversion and "Numeric Precedence" on page 2-13 for information on numeric precedence Note: To comply with emerging SQL standards, a future release of Oracle will give the INTERSECT operator greater precedence than the other set operators. Therefore, you should use parentheses to specify order of evaluation in queries that use the INTERSECT operator with other set operators.
- 501. Sorting Query Results SQL Queries and Subqueries 9-9 UNION Example The following statement combines the results of two queries with the UNION operator, which eliminates duplicate selected rows. This statement shows that you must match datatype (using the TO_CHAR function) when columns do not exist in one or the other table: SELECT location_id, department_name "Department", TO_CHAR(NULL) "Warehouse" FROM departments UNION SELECT location_id, TO_CHAR(NULL) "Department", warehouse_name FROM warehouses; LOCATION_ID Department Warehouse ----------- --------------------- -------------------------- 1400 IT 1400 Southlake, Texas 1500 Shipping 1500 San Francisco 1600 New Jersey 1700 Accounting 1700 Administration 1700 Benefits 1700 Construction ... UNION ALL Example The UNION operator returns only distinct rows that appear in either result, while the UNION ALL operator returns all rows. The UNION ALL operator does not eliminate duplicate selected rows: SELECT product_id FROM order_items UNION SELECT product_id FROM inventories; SELECT location_id FROM locations UNION ALL SELECT location_id FROM departments; A location_id value that appears multiple times in either or both queries (such as '1700') is returned only once by the UNION operator, but multiple times by the UNION ALL operator. INTERSECT Example The following statement combines the results with the INTERSECT operator, which returns only those rows returned by both queries: SELECT product_id FROM inventories INTERSECT SELECT product_id FROM order_items; MINUS Example The following statement combines results with the MINUS operator, which returns only unique rows returned by the first query but not by the second: SELECT product_id FROM inventories MINUS SELECT product_id FROM order_items; Sorting Query Results Use the ORDER BY clause to order the rows selected by a query. Sorting by position is useful in the following cases:
- 502. Joins 9-10 Oracle Database SQL Reference ■ To order by a lengthy select list expression, you can specify its position in the ORDER BY clause rather than duplicate the entire expression. ■ For compound queries containing set operators UNION, INTERSECT, MINUS, or UNION ALL, the ORDER BY clause must specify positions or aliases rather than explicit expressions. Also, the ORDER BY clause can appear only in the last component query. The ORDER BY clause orders all rows returned by the entire compound query. The mechanism by which Oracle Database sorts values for the ORDER BY clause is specified either explicitly by the NLS_SORT initialization parameter or implicitly by the NLS_LANGUAGE initialization parameter. You can change the sort mechanism dynamically from one linguistic sort sequence to another using the ALTER SESSION statement. You can also specify a specific sort sequence for a single query by using the NLSSORT function with the NLS_SORT parameter in the ORDER BY clause. Joins A join is a query that combines rows from two or more tables, views, or materialized views. Oracle Database performs a join whenever multiple tables appear in the FROM clause of the query. The select list of the query can select any columns from any of these tables. If any two of these tables have a column name in common, then you must qualify all references to these columns throughout the query with table names to avoid ambiguity. Join Conditions Most join queries contain at least one join condition, either in the FROM clause or in the WHERE clause. The join condition compares two columns, each from a different table. To execute a join, Oracle Database combines pairs of rows, each containing one row from each table, for which the join condition evaluates to TRUE. The columns in the join conditions need not also appear in the select list. To execute a join of three or more tables, Oracle first joins two of the tables based on the join conditions comparing their columns and then joins the result to another table based on join conditions containing columns of the joined tables and the new table. Oracle continues this process until all tables are joined into the result. The optimizer determines the order in which Oracle joins tables based on the join conditions, indexes on the tables, and, any available statistics for the tables. IA WHERE clause that contains a join condition can also contain other conditions that refer to columns of only one table. These conditions can further restrict the rows returned by the join query. Equijoins An equijoin is a join with a join condition containing an equality operator. An equijoin combines rows that have equivalent values for the specified columns. Depending on See Also: NLSSORT on page 5-104 and Oracle Database Globalization Support Guide for information on the NLS parameters Note: You cannot specify LOB columns in the WHERE clause if the WHERE clause contains the join condition. The use of LOBs in WHERE clauses is also subject to other restrictions. See Oracle Database Application Developer's Guide - Large Objects for more information.
- 503. Joins SQL Queries and Subqueries 9-11 the internal algorithm the optimizer chooses to execute the join, the total size of the columns in the equijoin condition in a single table may be limited to the size of a data block minus some overhead. The size of a data block is specified by the initialization parameter DB_BLOCK_SIZE. Self Joins A self join is a join of a table to itself. This table appears twice in the FROM clause and is followed by table aliases that qualify column names in the join condition. To perform a self join, Oracle Database combines and returns rows of the table that satisfy the join condition. Cartesian Products If two tables in a join query have no join condition, then Oracle Database returns their Cartesian product. Oracle combines each row of one table with each row of the other. A Cartesian product always generates many rows and is rarely useful. For example, the Cartesian product of two tables, each with 100 rows, has 10,000 rows. Always include a join condition unless you specifically need a Cartesian product. If a query joins three or more tables and you do not specify a join condition for a specific pair, then the optimizer may choose a join order that avoids producing an intermediate Cartesian product. Inner Joins An inner join (sometimes called a simple join) is a join of two or more tables that returns only those rows that satisfy the join condition. Outer Joins An outer join extends the result of a simple join. An outer join returns all rows that satisfy the join condition and also returns some or all of those rows from one table for which no rows from the other satisfy the join condition. ■ To write a query that performs an outer join of tables A and B and returns all rows from A (a left outer join), use the LEFT [OUTER] JOIN syntax in the FROM clause, or apply the outer join operator (+) to all columns of B in the join condition in the WHERE clause. For all rows in A that have no matching rows in B, Oracle Database returns null for any select list expressions containing columns of B. ■ To write a query that performs an outer join of tables A and B and returns all rows from B (a right outer join), use the RIGHT [OUTER] JOIN syntax in the FROM clause, or apply the outer join operator (+) to all columns of A in the join condition in the WHERE clause. For all rows in B that have no matching rows in A, Oracle returns null for any select list expressions containing columns of A. ■ To write a query that performs an outer join and returns all rows from A and B, extended with nulls if they do not satisfy the join condition (a full outer join), use the FULL [OUTER] JOIN syntax in the FROM clause. You can use outer joins to fill gaps in sparse data. Such a join is called a partitioned outer join and is formed using the query_partition_clause of the join_clause syntax. Sparse data is data that does not have rows for all possible values of a dimension such as time or department. For example, tables of sales data typically do See Also: "Using Join Queries: Examples" on page 19-38 See Also: "Using Self Joins: Example" on page 19-39
- 504. Joins 9-12 Oracle Database SQL Reference not have rows for products that had no sales on a given date. Filling data gaps is useful in situations where data sparsity complicates analytic computation or where some data might be missed if the sparse data is queried directly. Oracle recommends that you use the FROM clause OUTER JOIN syntax rather than the Oracle join operator. Outer join queries that use the Oracle join operator (+) are subject to the following rules and restrictions, which do not apply to the FROM clause OUTER JOIN syntax: ■ You cannot specify the (+) operator in a query block that also contains FROM clause join syntax. ■ The (+) operator can appear only in the WHERE clause or, in the context of left-correlation (that is, when specifying the TABLE clause) in the FROM clause, and can be applied only to a column of a table or view. ■ If A and B are joined by multiple join conditions, then you must use the (+) operator in all of these conditions. If you do not, then Oracle Database will return only the rows resulting from a simple join, but without a warning or error to advise you that you do not have the results of an outer join. ■ The (+) operator does not produce an outer join if you specify one table in the outer query and the other table in an inner query. ■ You cannot use the (+) operator to outer-join a table to itself, although self joins are valid. For example, the following statement is not valid: -- The following statement is not valid: SELECT employee_id, manager_id FROM employees WHERE employees.manager_id(+) = employees.employee_id; However, the following self join is valid: SELECT e1.employee_id, e1.manager_id, e2.employee_id FROM employees e1, employees e2 WHERE e1.manager_id(+) = e2.employee_id; ■ The (+) operator can be applied only to a column, not to an arbitrary expression. However, an arbitrary expression can contain one or more columns marked with the (+) operator. ■ A WHERE condition containing the (+) operator cannot be combined with another condition using the OR logical operator. ■ A WHERE condition cannot use the IN comparison condition to compare a column marked with the (+) operator with an expression. ■ A WHERE condition cannot compare any column marked with the (+) operator with a subquery. If the WHERE clause contains a condition that compares a column from table B with a constant, then the (+) operator must be applied to the column so that Oracle returns See Also: ■ join_clause on page 19-17 for more information about using outer joins to fill gaps in sparse data ■ Oracle Database Data Warehousing Guide for a complete discussion of group outer joins and filling gaps in sparse data
- 505. Using Subqueries SQL Queries and Subqueries 9-13 the rows from table A for which it has generated nulls for this column. Otherwise Oracle returns only the results of a simple join. In a query that performs outer joins of more than two pairs of tables, a single table can be the null-generated table for only one other table. For this reason, you cannot apply the (+) operator to columns of B in the join condition for A and B and the join condition for B and C. Please refer to SELECT on page 19-4 for the syntax for an outer join. Antijoins An antijoin returns rows from the left side of the predicate for which there are no corresponding rows on the right side of the predicate. That is, it returns rows that fail to match (NOT IN) the subquery on the right side. Semijoins A semijoin returns rows that match an EXISTS subquery without duplicating rows from the left side of the predicate when multiple rows on the right side satisfy the criteria of the subquery. Semijoin and antijoin transformation cannot be done if the subquery is on an OR branch of the WHERE clause. Using Subqueries A subquery answers multiple-part questions. For example, to determine who works in Taylor's department, you can first use a subquery to determine the department in which Taylor works. You can then answer the original question with the parent SELECT statement. A subquery in the FROM clause of a SELECT statement is also called an inline view. A subquery in the WHERE clause of a SELECT statement is also called a nested subquery. A subquery can contain another subquery. Oracle Database imposes no limit on the number of subquery levels in the FROM clause of the top-level query. You can nest up to 255 levels of subqueries in the WHERE clause. If columns in a subquery have the same name as columns in the containing statement, then you must prefix any reference to the column of the table from the containing statement with the table name or alias. To make your statements easier to read, always qualify the columns in a subquery with the name or alias of the table, view, or materialized view. Oracle performs a correlated subquery when a nested subquery references a column from a table referred to a parent statement any number of levels above the subquery. The parent statement can be a SELECT, UPDATE, or DELETE statement in which the subquery is nested. A correlated subquery is evaluated once for each row processed by the parent statement. Oracle resolves unqualified columns in the subquery by looking in the tables named in the subquery and then in the tables named in the parent statement. A correlated subquery answers a multiple-part question whose answer depends on the value in each row processed by the parent statement. For example, you can use a correlated subquery to determine which employees earn more than the average See Also: "Using Antijoins: Example" on page 19-42 See Also: "Using Semijoins: Example" on page 19-43
- 506. Unnesting of Nested Subqueries 9-14 Oracle Database SQL Reference salaries for their departments. In this case, the correlated subquery specifically computes the average salary for each department. Use subqueries for the following purposes: ■ To define the set of rows to be inserted into the target table of an INSERT or CREATE TABLE statement ■ To define the set of rows to be included in a vi