mysql - 无法在 FROM 子句中指定更新目标表 'assets'

Question

我的查询。

UPDATE assets SET assets.Amount = (SELECT SUM(assets.Amount) - NEW.Amount FROM assets WHERE NEW.UserId =   assets.UserId and NEW.AccountId = assets.AccountId) AS TmpAssets
WHERE NEW.UserId = assets.UserId and NEW.AccountId = assets.AccountId

Answer 1

MySQL 不允许您在更新或删除中使用在子查询中更新的表。解决这个问题很容易。

这是一种使用update/join的方法:

UPDATE assets a JOIN
       (select sum(a.Amount) as sumamount, a.UserId, a.AccountId
        from assets a
        where NEW.UserId = a.UserId and NEW.AccountId = a.AccountId
        group by a.UserId, a.AccountId
       ) anew
       on NEW.UserId = a.UserId and NEW.AccountId = a.AccountId
    SET a.Amount = anew.sumamount - new.Amount;