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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

ArgumentsDescription
expressionAny 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 |
+------+