Oracle: Functions
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This document discusses functions and the GROUP BY clause in Oracle. It covers single row functions like character, number, date functions and aggregate functions that operate on multiple rows. Examples are provided to demonstrate character functions like INITCAP, UPPER, SUBSTR and number functions like ROUND, TRUNC, MOD. Date functions like MONTH, YEAR and date arithmetic are also covered. Conversion, general functions like NVL, NVL2, NULLIF are explained. The syntax for aggregate functions like COUNT, MIN, MAX, AVG, SUM with the GROUP BY clause is demonstrated to group and filter results.
Oracle: Functions
- 1. 1Using ORACLE®Using functions(single row and aggregate functions)And the ‘GROUP BY ‘ clause
- 2. 2FUNCTIONSWe have many functions in Oracle that can be used to perform a myriad of tasks.There are two types of functions viz:Functions take input ,process it and provide the output.Single row functions operate only on one row (1 input and 1 output)Aggregate functions can operate on a range of rows ( multiple inputs and one output)
- 3. 3FUNCTIONSSingle row functions can be divided into different parts as:CharacterSingle row functionsNumberGeneralConversionDate
- 4. 4CHARACTER FUNCTIONSCase manipulation functionsCharacter manipulation functions
- 5. 5CHARACTER FUNCTIONSSELECTprod_ID, INITCAP (prod_name) , CONCAT ('Rs ',prod_cost) AS COST FROM product_masterWHERE prod_name LIKE( LOWER ('TEAK%'));SELECTprod_ID, UPPER (prod_name) , CONCAT ('Rs ',prod_cost) AS COST FROM product_masterWHERE prod_name LIKE ( CONCAT ( '%', SUBSTR ( 'teak_sofa', 6, 4 )));Equivalent to LIKE ( ‘%sofa’);
- 6. 6NUMBER FUNCTIONSSELECT ROUND (3.14126,4), TRUNC (3.14126,4) , MOD ( 22, 7 ) FROM DUAL ;(DUAL is a dummy table in Oracle used to perform calculations.)SELECTprod_ID , prod_name , ROUND( MOD (prod_stock,prod_order),0) AS REORDER_LVLFROM product_masterORDER BY REORDER_LVL;(Here we use the alias name to order the output)
- 7. 7DATE FUNCTIONSWe can use either MONTH or YEAR as parameters in the ROUND and TRUNC functions.
- 8. 8DATE MANIPULATIONSApart from the date functions we can also perform arithmetic operations on dates as:.Adding or subtracting a number to or from a date to get a resultant date.Subtracting two dates to find the number of days between those dates.Adding hours to a date by dividing the number of hours by 24.SELECT SYSDATEASTODAY, (SYSDATE+1) AS NEXT_DAY, (SYSDATE-1) AS PREV_DAYFROM DUAL;
- 9. 9CONVERSION FUNCTIONSHere in the TO_NUMBER function we are converting the string ‘2000’ to a number 2000.In TO_DATE we have to specify the format of the output date and In TO_CHAR we have to specify the format of input date to be converted to a string
- 10. 10GENERAL FUNCTIONSSELECT prod_ID, prod_name, NVL (prod_order,0), NVL2 (prod_sales,'YES','NO'), NULLIF (prod_stock,(prod_order+prod_sales)) AS NULLIFFROM product_master;
- 11. 11AGGREGATE FUNCTIONSAggregate functions take multiple rows as input and give one output. The SYNTAX is:SELECT column1,column2…….aggregate_function( column)…FROMtable_nameWHERE (expression/condition);
- 12. 12AGGREGATE FUNCTIONSSELECT COUNT (prod_ID) AS COUNT, MIN (prod_cost) AS MINIMUM, MAX (prod_sales) AS MAXIMUM, AVG (prod_cost) AS AVERAGE, SUM (prod_stock) AS SUM, ROUND( STDDEV (prod_sales),3) AS STD_DEVIAYION,ROUND( VARIANCE (prod_stock),3) AS VARIANCEFROM product_master;(We can also use ‘*’ in COUNT and ‘DISTINCT’ in AVG )
- 13. 13GROUP BY CLAUSEWhen we wish to divide the table into multiple groups based on some criterion we use the ‘GROUP BY’ clause.It is mandatory that while using a group by clause we include the column used in the group must not be used in a aggregate function in the SELECT statement.SYNTAX:SELECT column1,column2…….aggregate_function( column)…FROMtable_nameGROUP BY columnWHERE (expression/condition);It is mandatory to use the group by clause when displaying any column along with a aggregratefunction.We can also use multiple columns in the group by clause.Use the WHERE clause to furthur filter results.
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