Aggregate Functions

Aggregate Functions

MIN	Returns the smallest value in a given column
MAX	Returns the largest value in a given column
SUM	Returns the sum of the numeric values in a given column
AVG	Returns the average value of a given column
COUNT	Returns the total number of values in a given column
COUNT(*)	Returns the number of rows in a table

In database management system an aggregate function is a function where the values of multiple rows are grouped together as input and on certain criteria to form a single value. Aggregate functions are used to compute against a numeric column data from SELECT statement. This mostly summarize the results of a particular column of selected data. 

For example:

SELECT AVG (MARKS) FROM STUDENTS;

This statement will return a single result which contains the average value of everything returned in the Marks column from the Students table.

Another example:

SELECT AVG (SALARY) FROM EMPLOYEE WHERE TITLE=’AVP’;

This statement will return the average salary for all employee whose title is equal to AVP.

Example:

SELECT COUNT (*) FROM STUDENTS;

This statement returns the total number of students. However you can also add additional column or distinct values counts.

Example:-

SELECT COUNT (DISTINCT TITLE) FROM EMPLOYEE;