您无法指定目标表＆＃39;资产＆＃39;用于FROM子句中的更新

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update或delete的子查询中使用正在更新的表。这很容易解决这个问题。

以下是使用update / join的一种方法：

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;

Answer 2

是的，你不能这样做，因为你在更新它时从表中进行子选择。 你可以做的最好的事情是创建一个tmp表并执行它们的子查询。

Answer 3

试试这个：

 UPDATE assets SET assets.Amount = (select temp.val from (SELECT (SUM(assets.Amount) - 
 NEW.Amount) val from assets   WHERE
 NEW.UserId =   assets.UserId and NEW.AccountId = assets.AccountId) temp) 
 WHERE NEW.UserId = assets.UserId and NEW.AccountId = assets.AccountId ;