Change unique key together in mysql

问题

I have in my MYSQL table a unique key and i want to add to it.

UNIQUE KEY `user_id` (`user_id`,`account_id`)

and i want to add another

UNIQUE KEY `user_id` (`user_id`,`account_id`,`pet_id`)

回答1:

ALTER TABLE your_table 
   DROP INDEX user_id, 
   ADD UNIQUE KEY `user_id` (`user_id`,`account_id`,`pet_id`)

Note: You won't need the backticks around the column names if you're using mariadb on Linux - in fact it will throw an syntax error 1064/(42000)

回答2:

Drop the first key and then create the new one.

来源：https://stackoverflow.com/questions/20116140/change-unique-key-together-in-mysql