COUNT()

The COUNT() aggregate function returns the total number of rows that match the specified criteria.

Syntax

SELECT COUNT(column_name)
FROM table_name;

COUNT() takes the name of a column as an argument and counts the number of rows where the column is not NULL. The non NULL values are counted in the column that is passed in using the column_name.

When * or 1 are passed as an argument into COUNT(), the number of all rows, including NULL values, are included in the count.

Example

Suppose there’s an employees table with the following values:

To find the total number of rows in the employees table that have experience, the given query can be used:

SELECT COUNT(experience)
FROM employees;

The result would be:

COUNT(*) counts the number of rows including NULL values. COUNT(1) replaces all values not excluding NULL with 1, so it includes them in the count. Therefore, COUNT(*) and COUNT(1) have the same results.

To find the total number of rows in the employees table, the given query can be used:

SELECT COUNT(*)
FROM employees;

SELECT COUNT(1)
FROM employees;

Both queries above would result in a count of 4.