SQL COUNT Function

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

SELECT COUNT(column) FROM table

Example

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.