無法更新觸發器中的表

Question

我做了新的觸發器，它必須更新員工的工資。它從表格付款中獲取2個值（現金和月），並將它們分成一列「how_much_to_pay」。

我看了一下題目： MySQL triggers cannot update rows in same table the trigger is assigned to. Suggested workaround?

但didin't幫我，因爲他們只用1臺，它們可以把「新」沒有問題。

這裏是我的觸發器：

create trigger pay_out before insert on `payment_out` 
for each row 
then 
UPDATE `payment_out` o 
INNER JOIN payment p ON p.id_1 = o.id_1 AND o.id2 = p.id2 
SET o.`how_much_to_pay` = p.cash/p.months; 
end; 
$$ 

下面是表：

table payment_out 
id1 
id2 
how_much_to_pay 

table payment 
id1 
id2 
cash 
months 

和錯誤本身：

1442 - Can't update table payment_out in stored function/trigger because it is already used by statement which invoked this stored function/trigger. 

Answer 1

如果你有一個一對一的關係之間的兩個表，那麼你可以在BEFORE INSERT觸發器中使用這段代碼 -

BEGIN 
    SELECT p.cash, p.months INTO @cash, @months 
    FROM payment p 
    WHERE p.id_1 = NEW.id_1 AND p.id2 = NEW.id2; 

    SET NEW.how_much_to_pay = @cash/@months; 
END