删除唯一性约束unique

删除唯一性约束

语法如下：

alter table tableName drop index key_name;#删除唯一性约束，实际就是删除索引

drop index key_name on tableName; #两种方法均可

mysql> show create table t_user;
+--------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table  | Create Table                                                                                                                                                                                                                     |
+--------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| t_user | CREATE TABLE `t_user` (
  `id` int(10) DEFAULT NULL,
  `name` varchar(32) NOT NULL,
  `email` varchar(128) DEFAULT NULL,
  UNIQUE KEY `name` (`name`,`email`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci |
+--------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> alter table t_user drop index name;

mysql> show create table t_user;
+--------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table  | Create Table                                                                                                                                                                               |
+--------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| t_user | CREATE TABLE `t_user` (
  `id` int(10) DEFAULT NULL,
  `name` varchar(32) NOT NULL,
  `email` varchar(128) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci |
+--------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)