Count function in sql | sql count function

Count function in sql | sql count function 

Count Function

It returns number of rows in a table.

How it works

Count(*)

Syntax:

Select count(*) from employee;

It will counted all the rows in a table. If table has no rows, it will return 0.

Count(*)

or

Select count(*) from employee where salary>10000 and salary<20000;

It will counted all the rows whose salary is greater than 10000 and less than 20000.

Count Function with where clause

Count (column_name) 

In this, all the rows counted except null values but counted 0 value.

Syntax:

Select count(salary) from emp;

Count function with column name

Count(distinct column-name)

In this, All the rows counted except null values and duplicate values.

Syntax:

Select count(distinct salary) from emp;

Count function with distinct  keyword

See Also:

Database
Tables
Alter Command
Update Command