刪除唯一性約束unique

刪除唯一性約束

語法如下：

alter table tableName drop index key_name;#刪除唯一性約束，實際就是刪除索引

drop index key_name on tableName; #兩種方法均可

 

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)