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COUNT
Aggregate function. Counts the number of rows passed in. If the value of a given item is NULL, the row is not counted.
Syntax
COUNT ( [DISTINCT] expression )
Arguments
- DISTINCT: optional keyword. If present, will count the number of unique values.
- expression: any expression. This may be a column name, the result of another function, or a math operation. The special operator “*” is also allowed, to indicate pure row counting.
Return Type
An integer.
Examples
select count(*) from people;
+----------+
| count(*) |
+----------+
| 5000 |
+----------+
select count(middle_name) as middles from people;
+----------+
| middles |
+----------+
| 1238 |
+----------+
select count(DISTINCT middle_name) as middles from people;
+----------+
| middles |
+----------+
| 213 |
+----------+
