插入触发器后的MySQL更新

Question

I am new to triggers but have coded this one

DELIMITER $$

CREATE TRIGGER stockupdate
AFTER INSERT ON inventory.orderdetails
FOR EACH ROW

BEGIN

    UPDATE inventory.stockitem s
    INNER JOIN inventory.OrderDetails d ON s.ID = d.Item
    INNER JOIN inventory.orders o ON ebayOrderNumber = d.OrderNumber
    SET s.`Sold Date` = o.`Order Date`, s.EbayOrderNumber = o.ebayOrderNumber, s.`Sale Price` = d.Price
    WHERE s.ID = d.Item;

END$$

DELIMITER ;

Currently it does not update table stockitem as expected. Is there anything glaringly obvious that I have done wrong please?

Many thanks for looking.

Answer 1

That's because your join returns all or most records from oderDetails and oders table and you are not supressing sql_safe_updates safety feature.

You are definitely missing table alias in o ON ??.ebayOrderNumber = d.OrderNumber . Besides, WHERE s.ID = d.Item; is redundant as your table joins already do that. Your Where condition should be more explicit and tell which stock item to update.

DELIMITER $$

CREATE TRIGGER stockupdate    AFTER INSERT ON inventory.orderdetails    FOR EACH ROW
BEGIN

        UPDATE 
            (inventory.stockitem s
            INNER JOIN inventory.OrderDetails d ON s.ID = d.Item)
            INNER JOIN inventory.orders o       ON o.ebayOrderNumber = d.OrderNumber
        SET 
            s.`Sold Date`     = o.`Order Date`,  -- update the stock
            s.EbayOrderNumber = o.ebayOrderNumber,
            s.`Sale Price`    = d.Price
        WHERE
            d.orederNumber    = NEW.OrderNumber, -- From this order
            d.Item            = NEW.item; -- and this item id

END$$

DELIMITER ;

Having said that, I do not understand why would you want to update the stock table with a sold price? orderDetails already contains those for you and what if you have many quantity for a single stock? ie 100 Dell laptops. Surely you don't have 100 records for each Dell laptop in your stock item? and updating each record with sold price? Anyway i leave that up to you..