DROP INDEX

语法说明

该语句用于从当前所选的表中删除索引，如果索引不存在则会报错，除非使用 IF EXISTS 修饰符。

语法结构

1. > DROP INDEX index_name ON tbl_name

示例

1. create table t5(a int, b int, unique key(a));
2. mysql> show create table t5;
3. +-------+----------------------------------------------------------------------------------------+
4. | Table | Create Table                                                                           |
5. +-------+----------------------------------------------------------------------------------------+
6. | t5    | CREATE TABLE `t5` (
7. `a` INT DEFAULT NULL,
8. `b` INT DEFAULT NULL,
9. UNIQUE KEY `a` (`a`)
10. ) |
11. +-------+----------------------------------------------------------------------------------------+
12. 1 row in set (0.01 sec)

14. create index b on t5(b);
15. mysql> show create table t5;
16. +-------+-------------------------------------------------------------------------------------------------------+
17. | Table | Create Table                                                                                          |
18. +-------+-------------------------------------------------------------------------------------------------------+
19. | t5    | CREATE TABLE `t5` (
20. `a` INT DEFAULT NULL,
21. `b` INT DEFAULT NULL,
22. UNIQUE KEY `a` (`a`),
23. KEY `b` (`b`)
24. ) |
25. +-------+-------------------------------------------------------------------------------------------------------+
26. 1 row in set (0.02 sec)

28. drop index b on t5;
29. mysql> show create table t5;
30. +-------+----------------------------------------------------------------------------------------+
31. | Table | Create Table                                                                           |
32. +-------+----------------------------------------------------------------------------------------+
33. | t5    | CREATE TABLE `t5` (
34. `a` INT DEFAULT NULL,
35. `b` INT DEFAULT NULL,
36. UNIQUE KEY `a` (`a`)
37. ) |
38. +-------+----------------------------------------------------------------------------------------+
39. 1 row in set (0.02 sec)