COUNT
Aggregate function.
The COUNT() function returns the number of records returned by a select query.
Note: 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​
note
numbers(N) – A table for test with the single number column (UInt64) that contains integers from 0 to N-1.
mysql> SELECT count(*) FROM numbers(3);
+----------+
| count(*) |
+----------+
| 3 |
+----------+
mysql> SELECT count(number) FROM numbers(3);
+---------------+
| count(number) |
+---------------+
| 3 |
+---------------+
mysql> SELECT count(number) AS c FROM numbers(3);
+------+
| c |
+------+
| 3 |
+------+