COUNT
Description
Returns the number of non-NULL records in the specified column, or the total number of records.
Syntax
COUNT(DISTINCT <expr> [,<expr>,...])
COUNT(*)
COUNT(<expr>)Parameters
| Parameter | Description |
|---|---|
<expr> | Conditional expression (column name) |
Return Value
The return value is of numeric type. If expr is NULL, there will be no parameter statistics.
Example
select * from test_count;+------+------+------+
| id | name | sex |
+------+------+------+
| 1 | 1 | 1 |
| 2 | 2 | 1 |
| 3 | 3 | 1 |
| 4 | 0 | 1 |
| 4 | 4 | 1 |
| 5 | NULL | 1 |
+------+------+------+select count(*) from test_count;+----------+
| count(*) |
+----------+
| 6 |
+----------+select count(name) from test_insert;+-------------+
| count(name) |
+-------------+
| 5 |
+-------------+select count(distinct sex) from test_insert;+---------------------+
| count(DISTINCT sex) |
+---------------------+
| 1 |
+---------------------+select count(distinct id,sex) from test_insert;+-------------------------+
| count(DISTINCT id, sex) |
+-------------------------+
| 5 |
+-------------------------+