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)