Mysql SELECT 里面的 UPDATE

Mysql SELECT inside UPDATE(Mysql SELECT 里面的 UPDATE)

问题描述

UPDATE forms SET

pos = (SELECT MIN(pos)-1 FROM forms)

WHERE id=$id

这不起作用，错误消息:

This doesn't work, error message:

**You can't specify target table 'form' for update in FROM clause**

我希望很清楚:我想从同一张表中获取最小的 element-1 并将其分配给 pos

I hope it's clear: I want to get the minimal element-1 from the same table and assign it to pos

推荐答案

Consp 是对的，它不被支持.但是，有一个解决方法:

Consp is right that it's not supported. There's a workaround, however:

UPDATE forms SET
pos = (SELECT MIN(pos)-1 FROM (SELECT * FROM forms) AS x)
WHERE id=$id

可能更快的版本:

UPDATE forms 
SET pos = (SELECT pos-1 FROM (SELECT MIN(pos) AS pos FROM forms) AS x)
where id=$id

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