COUNT

The COUNT() function returns the number of records returned by a SELECT query.

警告

NULL values are not counted.

Syntax

COUNT(expression)

Arguments

Arguments	Description
expression	Any expression. This may be a column name, the result of another function, or a math operation. * is also allowed, to indicate pure row counting.

Return Type

An integer.

Examples

tip

numbers(N) – A table for test with the single number column (UInt64) that contains integers from 0 to N-1.

SELECT count(*) FROM numbers(3);
+----------+
| count(*) |
+----------+
|        3 |
+----------+

SELECT count(number) FROM numbers(3);
+---------------+
| count(number) |
+---------------+
|             3 |
+---------------+

SELECT count(number) AS c FROM numbers(3);
+------+
| c    |
+------+
|    3 |
+------+