1. 1 Using ORACLE® Using functions (single row and aggregate functions) And the ‘GROUP BY ‘ clause
2. 2 FUNCTIONS We 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. 3 FUNCTIONS Single row functions can be divided into different parts as: Character Single row functions Number General Conversion Date
5. 5 CHARACTER FUNCTIONS SELECTprod_ID, INITCAP (prod_name) , CONCAT ('Rs ',prod_cost) AS COST FROM product_master WHERE prod_name LIKE( LOWER ('TEAK%')); SELECTprod_ID, UPPER (prod_name) , CONCAT ('Rs ',prod_cost) AS COST FROM product_master WHERE prod_name LIKE ( CONCAT ( '%', SUBSTR ( 'teak_sofa', 6, 4 ))); Equivalent to LIKE ( ‘%sofa’);
6. 6 NUMBER FUNCTIONS SELECT 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_LVL FROM product_master ORDER BY REORDER_LVL; (Here we use the alias name to order the output)
7. 7 DATE FUNCTIONS We can use either MONTH or YEAR as parameters in the ROUND and TRUNC functions.
8. 8 DATE MANIPULATIONS Apart 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_DAY FROM DUAL;
9. 9 CONVERSION FUNCTIONS Here 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. 10 GENERAL FUNCTIONS SELECT prod_ID, prod_name, NVL (prod_order,0), NVL2 (prod_sales,'YES','NO'), NULLIF (prod_stock,(prod_order+prod_sales)) AS NULLIF FROM product_master;
11. 11 AGGREGATE FUNCTIONS Aggregate functions take multiple rows as input and give one output. The SYNTAX is: SELECT column1,column2…….aggregate_function( column)… FROMtable_name WHERE (expression/condition);
12. 12 AGGREGATE FUNCTIONS SELECT 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 VARIANCE FROM product_master; (We can also use ‘*’ in COUNT and ‘DISTINCT’ in AVG )
13. 13 GROUP BY CLAUSE When 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_name GROUP BY column WHERE (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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