Introduction to oracle database (basic concepts)

Introduction To Oracle Database
IT-3441
Lecture # 3
Jahanzaib Ali Khan

Oracle is an Relational Database
• Database in which all data is stored in Relations (Tables)
with rows and columns. Each table is composed of records
(called Tuples) and each record is identified by a field
(attribute) containing a unique value. Every table shares at
least one field with another table in 'one to one,' 'one to
many,' or 'many to many' relationships. These relationships
allow the database user to access the data in almost an
unlimited number of ways, and to combine the tables as
building blocks to create complex and very large
databases.
• The oracle database houses everything There is 1 database
which has multiple tablespaces, schemas,Datafiles and
segments.

Database Management System
• A database management system (DBMS) is software that controls
the storage, organization, and retrieval of data. Typically, a DBMS
has the following elements:
• A database application is a software program that interacts with a
database to access and manipulate data.
• The first generation of database management systems included the
following types:
• A hierarchical database organizes data in a tree structure. Each
parent record has one or more child records, similar to the
structure of a file system.
• A network database is similar to a hierarchical database, except
records have a many-to-many rather than a one-to-many
relationship.
• Current Model is Relational Database Model , Described Earlier.

What is Oracle Schema ??
• In simple terms a schema in an Oracle database is
another name for a user. So a schema and a user
are the same thing.
• SCHEMA = USER
• The purpose of a schema in Oracle is to house
database objects. The objects could be like tables
and indexes, or object definitions like views,
packages, triggers, etc. Hopefully image will help
you to understand the relationship between a
database, a schema, the segments in a schema
and the tablespace in which the segments reside.

More about Schema !!!
• 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
• Database links
• Database triggers
• Dimensions
• External procedure libraries
• Indexes and index types
• Java classes, Java resources, and Java sources
• Materialized views and materialized view logs
• Object tables, object types, and object views
• Operators
• Sequences
• Stored functions, procedures, and packages
• Synonyms
• Tables and index-organized tables
• Views

Table
• A table describes an entity such as employees. You define a
table with a table name, such as employees, and set of
columns. In general, you give each column a name, a data
type, and a width when you create the table.
• A table is a set of rows. A column identifies an attribute of
the entity described by the table, whereas a rowidentifies
an instance of the entity. For example, attributes of the
employees entity correspond to columns for employee ID
and last name. A row identifies a specific employee.
• You can optionally specify rules for each column of a table.
These rules are called integrity constraints. One example is
a NOT NULL integrity constraint. This constraint forces the
column to contain a value in every row.

Indexes
• An index is an optional data structure that you can
create on one or more columns of a table. Indexes can
increase the performance of data retrieval. When
processing a request, the database can use available
indexes to locate the requested rows efficiently.
Indexes are useful when applications often query a
specific row or range of rows.
• Indexes are logically and physically independent of the
data. Thus, you can drop and create indexes with no
effect on the tables or other indexes. All applications
continue to function after you drop an index.

Oracle Table Spaces
• This is a logical structure, meaning that a tablespace is not a
physical object
• A tablespace is made of 1 or more physical structures
called datafiles
• Each tablespace can have different characteristics, such as size and
how the size are managed
• They are used to group segments (tables, indexes, etc) into logical
groups. For example, you may have accounting data in
one tablespace and reporting data in another. This does not have to
be the case, though, you are free to put whatever you like in
the tablespacesyou create
• The SYSTEM and SYSAUX tablespaces are mandatory as of 10g, and
it is recommended to not put your own user created segments in
either of these tablespaces

Datafiles
• A datafile is a physical file on disk, just like any other
file which sits on a hard disk but in an Oracle format
• The datafile is created as part of a tablespace, and only
one tablespace
• You can set datafiles to autoextend which means they
they become full they will automatically
extend preventing users from running out of space
• For performance reasons, I would recommend having
fewer, larger datafiles rather than lots of small ones

The Oracle Schema or User
• Oracle Schema and user are synonymous and the
terms are usually used interchangeably
• There can be thousands of users within one database
• The schema owns segments (tables, indexes, etc) and
objects (views, constraints, etc) and each
segment/object can belong to only one schema
• Users can see segments and objects in other schemas if
they have been given the appropriate permissions
• If you have many schemas it is a good idea to
use Oracle roles to manage what privileges they have

Summing Up Things 
• In Oracle Database, a database schema is a collection of logical data
structures, or schema objects [i.e. related tables]. A database schema is
owned by a database user and has the same name as the user name.
• You can create multiple Oracle databases. Or you can create a single
database with multiple schemas. Or you can create a single database with
a single schema an put everything there if all your object names are
unique.
• A database consists of one or many tablespaces. A database has one-to-
many relationship with tablespaces. That is, one database can have many
tablespaces, but a given tablespace can belong to only one database.
• Similary, a tablespace has one-to-many relationship with datafiles. That is,
a tablespace can have one or many datafiles but a given datafile can
belong to only one tablespace.
• Database>>Schema>>TableSpace>>Datafiles

Data Access
• Structured Query Language:
• SQL is a non-procedural query language used to
operate with oracle Database.
• All operations on the data in an Oracle database are
performed using SQL statements. For example, you use
SQL to create tables and query and modify data in
tables. A SQL statement can be thought of as a very
simple, but powerful, computer program or
instruction. A SQL statement is a string of SQL text such
as the following:
• SELECT first_name, last_name FROM employees;

PL/SQL and Java
• PL/SQL is a procedural extension to Oracle SQL. PL/SQL is
integrated with Oracle Database, enabling you to use all of the
Oracle Database SQL statements, functions, and data types. You can
use PL/SQL to control the flow of a SQL program, use variables, and
write error-handling procedures.
• A primary benefit of PL/SQL is the ability to store application logic
in the database itself. A PL/SQL procedureor function is a schema
object that consists of a set of SQL statements and other PL/SQL
constructs, grouped together, stored in the database, and run as a
unit to solve a specific problem or to perform a set of related tasks.
The principal benefit of server-side programming is that built-in
functionality can be deployed anywhere.
• Oracle Database can also store program units written in Java. A Java
stored procedure is a Java method published to SQL and stored in
the database for general use. You can call existing PL/SQL programs
from Java and Java programs from PL/SQL.

Practical Task !!!
• Open then login into Oracle 11g Express by
typing your username and password
• Create New Workspace
• Goto Application Express
• Create a sample project

Introduction to oracle database (basic concepts)

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