mysql - 插入后MySql触发器更新选择总和

Question

我有三张桌子。

1. 成员
2. 账户
3. 交易

在将新事务插入 Transactions 表后，我想用所有 Transactions.TransactionAmount 的总和更新 Accounts.AccountBalance。

以下代码似乎对我不起作用。有什么建议么？

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，因此请尝试包装INSERT并UPDATE进入这样的存储过程

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);

这是该场景的SQLFiddle演示。