插入后MySql触发器更新选择总和

Question

我有三个表。

1. 成员
2. 帐户
3. 交易

在将新交易插入交易表后，我想用所有交易的总和更新 Accounts.AccountBalance.TransactionAmount。

下面的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。

UPDATE: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);

这是 SQLFiddle 该场景的演示。