SQL trigger: BEFORE UPDATE OF

Question

I have a following schema in my sqlite3 database.

It is a table that stores user's bid on a product, and triggers that I use to offload a validity check from my application code.

The goal here is to check whether a new bid is larger than the previous one and if not then raise an error to the application. It works well for INSERT , but UPDATE raises error even when NEW.amount is actually the largest bid for a given product.

I cannot figure out why is this happening mainly because triggers are impossible to debug. A suggestion on this would also be greatly appreciated.

CREATE TABLE IF NOT EXISTS bids (
    amount INTEGER NOT NULL,
    product_id INTEGER NOT NULL,
    user_id INTEGER NOT NULL,
    submitted DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP
);

CREATE TRIGGER IF NOT EXISTS trig_beforeinsert BEFORE INSERT ON bids
BEGIN
    SELECT CASE
        WHEN
            ((SELECT MAX(amount) FROM bids WHERE product_id = NEW.product_id) >= NEW.amount)
        THEN
            RAISE (FAIL, "invalid amount")
    END;
END;

CREATE TRIGGER IF NOT EXISTS trig_beforeupdate_amount BEFORE UPDATE OF amount ON bids
BEGIN
    SELECT CASE
        WHEN
            ((SELECT MAX(amount) FROM bids WHERE product_id = OLD.product_id) >= NEW.amount)
        THEN
            RAISE (FAIL, "invalid amount")
    END;
END;

Answer 1

实际上这是一个特定于应用程序的错误，我可以在发布之前找到它。