需要前一个事件的字段的 MySQL 触发器

Question

我还有一个触发问题，在我解释之前，我要给你看一个代码:

DELIMITER $$

CREATE PROCEDURE transferFunds ( receiver INT, sender INT, amount FLOAT )

BEGIN

  DECLARE senderBalance FLOAT;
  DECLARE receiverBalance FLOAT;

  SELECT balance INTO senderBalance 
    FROM accounts 
   WHERE accountNumber = sender;

  SELECT balance INTO receiverBalance 
    FROM accounts 
   WHERE accountNumber = receiver;

  SET autocommit = 0;

  UPDATE accounts
     SET balance = senderBalance - amount
   WHERE accountNumber = sender;

  UPDATE accounts
     SET balance = receiverBalance + amount
   WHERE accountNumber = receiver;

  IF senderBalance < amount THEN
    ROLLBACK;
  ELSE
    COMMIT;
  END IF;

END$$

CREATE TRIGGER transferTrigger AFTER UPDATE ON accounts
FOR EACH ROW
BEGIN

  -- Insert the Receiver and Sender and Amount to transfer_log table

END$$

我想创建一个触发器来记录刚刚发生的传输，但我做不到，因为触发器在每行事件中工作。如果我想在 transfer_log 表中记录转账事件并插入收件人和发件人帐号以及转账金额，我该怎么做？

Answer 1

正如您在问题中所述，触发器按行工作。

您应该直接在存储过程中进行日志记录。但是，您可以使用变通方法，但我认为它不安全 - 特别是在处理货币交易时(如 OP 所示)。

在你的存储过程中:

SET @TranSender = sender;
SET @TranReceiver = receiver;
...

在你的触发器中:

INSERT log_table(Sender, Receiver...)
VALUES (@TranSender , @TranReceiver...)