Aggregate Functions in MySQL

Aggregate Functions are those functions which are used in SQL. They return a single value which is calculated from values in the columns from a particular table.

The aggregate functions are below:

AVG()- It returns a average value
COUNT() - It returns the number of rows in a table
MAX() - It returns the maximum value stored in a table
MIN() - It returns the minimum value stored in a table
SUM() - It returns the sum of all the values of specified column



AVG() Function

Syntax:

SELECT AVG(column_name) FROM tblname;

For example:

Let's consider table called "tbl_salary" below:

sid	eid	salary
1	1	20000

Now if you want to find the average salary of employees working in a company then use AVG() function as below:

SELECT AVG(salary) AS AverageSalary FROM tbl_salary 



COUNT() Function

To count specific number of values in a specified column.

Syntax:
SELECT COUNT(column_name) FROM tblname

To count number of records in a table

Syntax:
SELECT COUNT(*) FROM tblname

For example:
Let's consider above table and use COUNT function as below:

SELECT COUNT(salary) as Num FROM tbl_salary

Another SQL

SELECT COUNT(*) as TotalRow FROM tbl_salary


MAX Function

Syntax

SELECT MAX(column_name) FROM tblname

 For example:

SELECT MAX(salary) AS MaxSalary FROM tbl_salary


MIN Function

Syntax

SELECT MIN(column_name) FROM tblname

For example:

SELECT MIN(salary) AS MinSalary FROM tbl_salary


SUM Function

Syntax

SELECT SUM(column_name) FROM tblname

For example:

SELECT SUM(salary) AS TotalSalary FROM tbl_salary