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)