您无法在FROM子句中为更新指定目标表“资产”

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不允许您使用update或delete子查询中正在更新的表。解决这个问题很容易。

下面是使用update/join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。 你可以做的最好的是创建一个tmp表并从那里执行子查询。

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 ;