Question

我有三张桌子。

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我想在将新事务插入到Transactions表中后，将所有Transactions.TransactionAmount的总和更新为Accounts.AccountBalance。

以下代码似乎对我不起作用。有什么建议吗？

CREATE TRIGGER NewTrigger
    AFTER INSERT ON Transactions
    FOR EACH ROW 
    BEGIN
        UPDATE Accounts SET Accounts.AccountBalance = (
                SELECT SUM(Transactions.TransactionAmount) 
                    FROM Transactions
                    WHERE Accounts.AccountID=Transactions.AccountID
        )

Answer 1

尝试

CREATE TRIGGER NewTrigger 
AFTER INSERT ON Transactions
FOR EACH ROW
UPDATE Accounts a
   SET a.AccountBalance = 
    (SELECT SUM(TransactionAmount) 
       FROM Transactions
      WHERE AccountID = a.AccountID)
 WHERE a.AccountID = NEW.AccountID;

这是 SQLFiddle 演示。

更新：由于您无法使用触发器，请尝试将INSERT和UPDATE包装到这样的存储过程中

DELIMITER $$
CREATE PROCEDURE AddTransaction(IN aid INT, amount DECIMAL(11, 2)) 
BEGIN
  START TRANSACTION;
  INSERT INTO Transactions (AccountID, TransactionAmount)
  VALUES (aid, amount);
  UPDATE Accounts a
     SET a.AccountBalance = 
      (SELECT SUM(TransactionAmount) 
         FROM Transactions
        WHERE AccountID = a.AccountID)
   WHERE a.AccountID = aid;
   COMMIT;
END $$
DELIMITER ;

然后使用它

CALL AddTransaction(1, 10.50);

以下是针对该方案的 SQLFiddle 演示。

插入后，MySql触发器更新选择总和

1 个答案: