ERROR 1093 (HY000): You can't specify target table 'a' for update in FROM clause

问题:

I have this query

UPDATE trh_adminLoginDate SET superseded = true WHERE EXISTS   (SELECT * FROM trh_adminLoginDate AS a2 WHERE a2.adminId = a.adminId AND a2.loginDate > a.loginDate AND a2.clientPlatform = a.clientPlatform) 

and table look like this.

+----------------+--------------+------+-----+---------+----------------+ | Field          | Type         | Null | Key | Default | Extra          | +----------------+--------------+------+-----+---------+----------------+ | id             | bigint(20)   | NO   | PRI | NULL    | auto_increment | | dateCreated    | datetime     | NO   |     | NULL    |                | | version        | int(11)      | NO   |     | NULL    |                | | dateModified   | datetime     | NO   |     | NULL    |                | | adminId        | bigint(20)   | NO   | MUL | NULL    |                | | clientPlatform | varchar(255) | YES  |     | NULL    |                | | loginDate      | datetime     | YES  |     | NULL    |                | | superseded     | tinyint(1)   | NO   |     | NULL    |                | +----------------+--------------+------+-----+---------+----------------+ 

When I execute this query I get the below error:

ERROR 1093 (HY000): You can't specify target table 'a' for update in FROM clause 

I can create temporary table and keep the result of the sub-query and then do the UPDATE. But I don't want to do in this way. Can someone suggest me better way of doing this?

回答1:

You are using the alias "a" but you never define it.

Perhaps this would work:

UPDATE  trh_adminLoginDate a          JOIN trh_adminLoginDate AS a2          ON a2.adminId = a.adminId          AND a2.loginDate > a.loginDate          AND a2.clientPlatform = a.clientPlatform  SET a.superseded = true 

回答2:

Or perhaps this will do the trick:

UPDATE trh_adminLoginDate a  SET    superseded = true   WHERE EXISTS        (SELECT * FROM trh_adminLoginDate WHERE adminId = a.adminId AND loginDate > a.loginDate AND clientPlatform = a.clientPlatform) 

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