Mysql compare rows same table then add another table - mysql

Question

i have a mysql products table like that;
http://www.sqlfiddle.com/#!9/56ac8e/2
when each line is added, I want it to compare with the latest price of the same coded product. if it is cheaper than the latest price, I want it to add rows to another table in the following way.
discount table is ;
http://www.sqlfiddle.com/#!9/c2227d/1
i changed the codes in the form of the link below, but it didn't work.
Compare rows in same table in mysql
CREATE DEFINER = CURRENT_USER TRIGGER `database`.`products_AFTER_INSERT` AFTER INSERT ON `products` FOR EACH ROW
BEGIN
WHERE NEW.product_id = OLD.product_id
IF NEW.price < OLD.price
THEN
INSERT INTO discount
(
id (auto) ,
product_id,
name ,
old.price ,
new.price ,
discount ((old.price / new.price )/10)
);
END IF;
END$$
can you help me in this regard ?

Answer 1

Solved. Akina Thank You..
https://dbfiddle.uk/fbeR9LTE
CREATE TABLE products (
id INT AUTO_INCREMENT PRIMARY KEY,
product_id CHAR(7),
name VARCHAR(255),
price DECIMAL(10, 2),
`date` DATETIME,
url VARCHAR(768)
);
CREATE TABLE discount (
product_id CHAR(7) PRIMARY KEY,
name varchar(255),
old_price DECIMAL(10, 2),
new_price DECIMAL(10, 2),
discount DECIMAL(3, 2),
url VARCHAR(768)
);
CREATE TRIGGER tr_bi_discount
BEFORE INSERT ON products
FOR EACH ROW
BEGIN
DECLARE prev_price DECIMAL(10, 2);
SELECT price INTO prev_price FROM products WHERE product_id = NEW.product_id ORDER BY `date` DESC LIMIT 1;
IF NEW.price < prev_price THEN
REPLACE INTO discount
SELECT NEW.product_id, NEW.name, prev_price, NEW.price, 1 - NEW.price / prev_price, NEW.url;
END IF;
END
INSERT INTO products (product_id, name, price, `date`, url) VALUES
('AD12CDS', 'iphone 13', 790.00, '2022-09-13 15:05', 'https://www.abcde.com.tr/1'),
('DDSC22S', 'samsung s22', 989.00, '2022-09-14 15:05', 'https://www.abcde.com.tr/2'),
('SDX10XA', 'xioami a10', 540.00, '2022-09-15 15:05', 'https://www.abcde.com.tr/3'),
('SDX10XA', 'xioami a10', 539.00, '2022-09-16 15:05', 'https://www.abcde.com.tr/4'),
('DDSC22S', 'samsung s22', 990.00, '2022-09-17 15:05', 'https://www.abcde.com.tr/5'),
('DDSC22S', 'samsung s22', 800.00, '2022-09-18 15:05', 'https://www.abcde.com.tr/6'),
('AD12CDS', 'iphone 13', 800.00, '2022-09-19 15:05', 'https://www.abcde.com.tr/7'),
('AD12CDS', 'iphone 13', 600.00, '2022-09-20 15:05', 'https://www.abcde.com.tr/8'),
('AA11SDE', 'ipnone 12', 500.00, '2022-09-21 15:05', 'https://www.abcde.com.tr/9'),
('DFR12SD', 'samsung s20', 400.00, '2022-09-22 15:05', 'https://www.abcde.com.tr/10');
SELECT * FROM products;
SELECT * FROM discount;