SQL COUNT() Function

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COUNT is a simple aggregate function provided by SQL. As it is clear from its name that it simply counts the number of records in the table and returns the total count.

There are three (3) different usage for the Count function.

• SQL COUNT(column_name)
  
• COUNT(*)
  
• COUNT(DISTINCT column_name)
  

Consider the following table for this exercise

Employess

Firstname

Lastname

Salary

DeptID

John

Smith

1000

1

Mathew

Simon

3000

1

Bill

Steve

2200

1

Amanda

Rogers

2

Steve

Hills

2800

2

Steve

jobs

2400

2

bill

cosby

700

3

SQL COUNT(column_name) Syntax

SELECT

COUNT

(

Salary)

FROM

TABLE

This syntax will count the number of values in a row excluding the NULL value.

Example

SELECT

COUNT

(

Firstname)

AS

Employee_with_Salary FROM

Employees

Result of the Query

Employee_with_Salary

6

SQL COUNT(*) Syntax

SELECT

COUNT

(

*

)

FROM

TABLE_NAME

This syntax will count all records in your table.

Example

SELECT

COUNT

(

*

)

AS

Total_Employee FROM

Employees

Result of the Query

Total_Employee

7

SQL COUNT(DISTINCT column_name) Syntax

SELECT

COUNT

(

DISTINCT

column_name)

FROM

TABLE_NAME

This syntax works the same as the SQL DISTINCT Clause that we have discussed in our previous chapter, except that it will return a distinct record on specific field.

Example

SELECT

COUNT

(

Firstname)

AS

Unique_Employee_Name FROM

Employees

Result of the Query

Unique_Employee_Name

6

As you can see on the above sample, you can also give an Alias to the Count function.

The Counter function will simply increments its value up to the last record in your table.