MySQL update 嵌套 select

当你希望更新一批值，且值是通过select条件查询出来时，下面这个错误应该不陌生

You can’t specify target table ‘x’ for update in FROM clause。

错误示范 1: A B 有关联同一个key_id , 根据 B表符合条件 -> 更新A表val值。

UPDATE A a SET a.val = 2

WHERE a.id IN ( SELECT a.id FROM A

LEFT JOIN B ON b.key_id = a.key_id

WHERE b.satisfy = 1)

解决思路 1: 使用 INNER JOIN (最简洁)

UPDATE A a INNER JOIN B b ON b.key_id = a.key_id

SET a.val = 2 WHERE b.satisfy = 1

解决思路 2:

UPDATE A a, (SELECT A.id from A

LEFT JOIN B ON B.key_id= A.key_id

WHERE B.satisfy = 1) b

SET a.val = 2

WHERE a.id = b.id

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