IS NOT NULL

语法说明

IS NOT NULL 运算符用于判断列的值是否为空。如果值不为空，即不为 NULL，则返回 true，否则返回 false。它可以用于 SELECT、INSERT、UPDATE 或 DELETE 语句。

语法结构

1. > expression IS NOT NULL

示例

1. mysql> SELECT 1 IS NOT NULL, 0 IS NOT NULL, NULL IS NOT NULL;
2. +---------------+---------------+------------------+
3. | 1 is not null | 0 is not null | null is not null |
4. +---------------+---------------+------------------+
5. | true          | true          | false            |
6. +---------------+---------------+------------------+
7. 1 row in set (0.01 sec)

1. create table t1 (a boolean,b bool);
2. insert into t1 values (0,1),(true,false),(true,1),(0,false),(NULL,NULL);

4. mysql> select * from t1;
5. +-------+-------+
6. | a     | b     |
7. +-------+-------+
8. | false | true  |
9. | true  | false |
10. | true  | true  |
11. | false | false |
12. | NULL  | NULL  |
13. +-------+-------+
14. mysql> select * from t1 where b is NOT NULL;
15. +-------+-------+
16. | a     | b     |
17. +-------+-------+
18. | false | true  |
19. | true  | false |
20. | true  | true  |
21. | false | false |
22. +-------+-------+
23. 4 rows in set (0.01 sec)