Mysql SELECT 里面的 UPDATE [英] Mysql SELECT inside UPDATE
本文介绍了Mysql SELECT 里面的 UPDATE的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
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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