AND,&&

运算符说明

AND,&& 逻辑运算符用作于逻辑与运算。如果所有操作数都非零且不为 NULL，则返回结果为 true；如果一个或多个操作数为 0，则返回结果为 false；如果一个或多个操作数非零且为 NULL，则返回 NULL。

语法结构

1. > SELECT column_1 AND column_2 FROM table_name;

示例

1. mysql> select 1 and 1;
2. +---------+
3. | 1 and 1 |
4. +---------+
5. | true    |
6. +---------+
7. mysql> select 1 and 0;
8. +---------+
9. | 1 and 0 |
10. +---------+
11. | false   |
12. +---------+
13. mysql> select 1 and null;
14. +------------+
15. | 1 and null |
16. +------------+
17. | NULL       |
18. +------------+
19. mysql> select null and 0;
20. +------------+
21. | null and 0 |
22. +------------+
23. | false      |
24. +------------+
25. 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);
3. mysql> select a and b from t1;
4. +---------+
5. | a and b |
6. +---------+
7. | false   |
8. | false   |
9. | true    |
10. | false   |
11. | NULL    |
12. +---------+
13. 5 rows in set (0.00 sec)