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 |
+------+------+------+
selectcount(*)from test_count;
+----------+
| count(*) |
+----------+
| 6 |
+----------+
selectcount(name)from test_insert;
+-------------+
| count(name) |
+-------------+
| 5 |
+-------------+
selectcount(distinct sex)from test_insert;
+---------------------+
| count(DISTINCT sex) |
+---------------------+
| 1 |
+---------------------+
selectcount(distinct id,sex)from test_insert;
+-------------------------+
| count(DISTINCT id, sex) |
+-------------------------+
| 5 |
+-------------------------+