SQL Count Functions

















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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 DISTINCT COUNT(column(s)) 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 DISTINCT COUNT(Company) FROM Orders

Will return this result:

3

 




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