Mysql 你可以'；t指定目标表'；资产'；for update in FROM子句

我的问题

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

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是的，您不能这样做，因为您在更新表时正在从表中进行子选择。

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您最好创建一个tmp表并从中执行子查询。

MySQL不允许您在

update

或

delete

的子查询中使用正在更新的表。解决这个问题很容易

下面是一种使用

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;

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 ;

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问得好，但我有个问题。我在表中有两条记录，金额分别为20和30，这两条金额随新条目而更改，我需要两条记录（50）的总数，然后更改。非常需要help@PutraLZendrato . . . 然后更改子查询以聚合所需的值。此版本似乎与您试图对问题中的查询执行的操作相同。