SQL Functions:

Aggregate Functions:

In SQL, there are several aggregate functions that allow you to perform calculations on set of values.

These functions operate on group of rows and return a single value.

1. SUM():

SUM functions returns the sum of all values.

Syntax:

SELECT SUM(column_name)

From table_name;

Example 1:

Find the total salary of all employees from Each Department:

SELECT Dept_ID, SUM(Salary)

From Employee

GROUP BY Dept_ID;

Use an alias:

Give a summarized Column a name by using AS keyword.

SELECT SUM(Salary) As TotalSalary

From Employee;

COUNT() :

This function returns the number of rows that matches the specified condition.

Syntax:

SELECT COUNT(Column_name) From table_name;

Example:

SELECT COUNT(EmpID) As NumberOfEmployees

From Employee;

Example 2:

Find the number of employee where salary is higher than 20000

SELECT COUNT(EmpID)

From Employee

Where salary > 20000;

MAX() AND MIN():

MAX() function returns the largest value of selected column

MIN() function returns the smallest value of selected column.

Syntax for Max():

SELECT MAX(Column_name)

From table_name;

Example:

SELECT MAX(Salary)

From Employee;

Syntax for MIN():

SELECT MIN(Column_name)

From table_name;

Example:

SELECT MIN(Salary)

From Employee;

AVG():

This function returns the average value of numeric column.

Syntax:

SELECT AVG(Column_name)

FROM table_name;

Example:

SELECT AVG(salary)

FROM Employee;

Use an alias:

SELECT AVG(salary) as AveragePrice

From Employee;