What are AGGREGATE FUNCTIONS?

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FUNCTIONS : These functions operate over a set of values.They are also known as aggregate functions

MAX(): A function used find maximum value among the given values.

SQL > SELECT MAX(SAL) FROM EMP;

MAX(SAL)
---------
5000

MIN(): It returns minimun of the values in a column.

SQL > SELECT MIN(HIREDATE) FROM EMP;

MIN(HIRED
---------
17-DEC-80

AVG(): Gives the average of values in a column.

SQL >SELECT AVG(SAL) FROM EMP;

AVG(SAL)
----------
2073.21429

SUM(): Sum of the values in a column

SQL >SELECT SUM(SAL) FROM EMP;

SUM(SAL)
----------
29025

COUNT(*): Gives number of columns in a table.

SQL >SELECT COUNT(*) FROM DUAL;

COUNT(*)
----------
1

SQL >SELECT COUNT(*) FROM EMP;

COUNT(*)
----------
14

COUNT(): Gives no of not null ENTRIE (VALUES) in that column.

SQL >SELECT COUNT(COMM) FROM EMP;

COUNT(COMM)
-----------
4

SQL >SELECT COUNT(DISTINCT JOB) FROM EMP;

COUNT(DISTINCTJOB)
------------------
5

Explanation: Using DISTICT, duplicate values can be suppressed.

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