SQL Function

Aggregate functions

Aggregate functions operate against a collection of values, but return a single value.

Note: If used among many other expressions in the item list of a SELECT statement, the SELECT must have a GROUP BY clause!!

Following are SQL Aggregate Functions with their description:

Syntax:

SELECT function_name(column_name) FROM table_name

Example for the Employee table below:

We key in the query

SELECT Avg(Salary) FROM Employee

will yield the result set that shows the average salary of the employees:

Similarly we can use the sum function to Add all the numeric values in the selected table by typing in the following query:

Lets take an example using Max function to find out the maximum value from the field-Age. We type the following query:

SELECT Max(Age) FROM Employee;

which results in:

Similarly we can use MIn function to find the minimum value from a column

We key in another query which is slightly different from others because he function that we use here i.e, count(*), is not supplied with any column, as shown below:

SELECT Count(*) FROM Employee

The above statement returns total number of rows in the Employee table i.e