Question

CREATE TRIGGER history BEFORE UPDATE ON bestbuy

 FOR EACH ROW
 BEGIN
 IF NEW.salePrice <> OLD.salePrice THEN

 INSERT INTO history_price (modelNumber,salePrice)
        VALUES (OLD.modelNumber,OLD.salePrice);

        ELSEIF NEW.salePrice = OLD.salePrice THEN
            SET NEW.salePrice = OLD.salePrice;

    END IF;

 END

My question:
is it valid to use

CREATE TRIGGER history BEFORE REPLACE ON bestbuy

Answer 1

No, it is not – valid events are only INSERT, UPDATE and DELETE.

Are you sure you are updating data with REPLACE? – you could change that, to update it with INSERT ... ON DUPLICATE KEY UPDATE – so your trigger will run

Edit to address the comments

take a look at INSERT … ON DUPLICATE KEY UPDATE Syntax on the MySQL site – it’s an ordinary INSERT, with a clause in it – I also think its a better performer than REPLACE, because this does not delete the record to insert it again, it just updates the values