SQL Count Functions

SQL has built-in functions for counting database records.

Count Function Syntax

The syntax for the built-in COUNT functions is:

SELECT COUNT(column) FROM table

Function COUNT(*) 

The COUNT(*) function returns the number of selected rows in a selection.

With this "Persons" Table:

Name	Age
Hansen, Ola	34
Svendson, Tove	45
Pettersen, Kari	19

This example returns the number of rows in the table:

SELECT COUNT(*) FROM Persons

Result:

3

This example returns the number of persons that are older than 20 years:

SELECT COUNT(*) FROM Persons WHERE Age>20

Result:

2

 

Function COUNT(column)

The COUNT(column)  function returns the number of rows without a NULL value in the specified column.

With this "Persons" Table:

Name	Age
Hansen, Ola	34
Svendson, Tove	45
Pettersen, Kari

This example finds the number of persons with a value in the "Age" field in the "Persons" table:

SELECT COUNT(Age) FROM Persons

Result:

2

The COUNT(column) function is handy for finding columns without a value. Note that the result is one less than the number of rows in the original table because one of the persons does not have an age value stored.

COUNT DISTINCT

The keyword DISTINCT and COUNT can be used together to count the number of distinct results.

The syntax is:

SELECT COUNT(DISTINCT column) FROM table

With this "Orders" Table:

Company	OrderNumber
Sega	3412
W3Schools	2312
Trio	4678
W3Schools	6798

This SQL statement:

SELECT COUNT(Company) FROM Orders

Will return this result:

4

This SQL statement:

SELECT COUNT(DISTINCT Company) FROM Orders

Will return this result:

3