MySql 触发器不起作用

Question

我有 3 table

tbl_payments(pay_id,date,amount,description,-------)
tbl_pay_trans(pay_id,trans_id)
tbl_transactions(trans_id,trans_date,trans_amount,trans_description,-----)

'tbl_transaction' 具有来自 'tbl_payments' 的相同数据以及一些其他值。为了保持两个 table 之间的关系，我使用 'tbl_pay_trans'。我想要做的是，当对 tbl_payments(amount,description) 进行更新时，需要在 tbl_transactions(trans_amount,trans_description) 中进行相同的更改。我写了一个触发器来执行此操作，但它没有按预期更新 tbl_transaction table 值。

我的触发器是

DELIMITER $$
CREATE TRIGGER update_trans 
    AFTER UPDATE on tbl_payments
    FOR EACH ROW
BEGIN
    DECLARE new_amount VARCHAR(50);
    DECLARE new_description TEXT;
    DECLARE new_pay_id,new_trans_id INT;

    SET new_pay_id = OLD.pay_id;
    SET new_amount = OLD.amount;
    SET new_description = OLD.description;
    SELECT trans_id INTO new_trans_id FROM tbl_pay_trans WHERE pay_id = new_pay_id;

    UPDATE tbl_transactions SET 
    trans_amount = new_amount,
    trans_description = new_description
    WHERE trans_id = new_trans_id;
END$$
DELIMITER ;

请有人帮我找出我做错了什么。

Answer 1

它没有更新，因为您在需要使用 NEW 的 amount 和 description 列上使用 OLD，即

SET new_amount = NEW.amount;
SET new_description = NEW.description;

OLD 指的是在更新发生在 tbl_payments 之前的列值。见 manual.

MySql 触发器不起作用

MySql trigger not works

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triggers

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sql-update