MySQL中买菜系统的推荐商品表设计方法

id int NOT NULL AUTO_INCREMENT,
user_id int NOT NULL,
product_id int NOT NULL,
recommend_time datetime NOT NULL,
PRIMARY KEY (id),
INDEX user_id_index (user_id),
INDEX product_id_index (product_id)

order_id int NOT NULL AUTO_INCREMENT,
user_id int NOT NULL,
product_id int NOT NULL,
order_time datetime NOT NULL,
PRIMARY KEY (order_id),
INDEX user_id_index (user_id),
INDEX product_id_index (product_id)

INSERT INTO recommendation (user_id, product_id, recommend_time)
VALUES (NEW.user_id, NEW.product_id, NOW());

id int NOT NULL AUTO_INCREMENT,
user_id int NOT NULL,
product_id int NOT NULL,
rating int NOT NULL,
PRIMARY KEY (id),
INDEX user_id_index (user_id),
INDEX product_id_index (product_id)

DECLARE i, j INT;
DECLARE user1_id, user2_id, product_id INT;
DECLARE similarity FLOAT;

-- 定义游标
DECLARE cur CURSOR FOR
    SELECT user_id, product_id FROM preference;
DECLARE CONTINUE HANDLER FOR NOT FOUND
    SET done = 1;

-- 循环遍历用户
OPEN cur;
read_loop: LOOP
    FETCH cur INTO user1_id, product_id;
    IF done THEN
        LEAVE read_loop;
    END IF;

    -- 查询与当前用户喜好相似的其他用户
    SELECT user_id, rating INTO user2_id, similarity
    FROM preference
    WHERE user_id != user1_id
    ORDER BY ABS(rating - (SELECT rating FROM preference WHERE user_id = user1_id))
    LIMIT 5;

    -- 插入推荐商品记录
    INSERT INTO recommendation (user_id, product_id, recommend_time)
    SELECT user2_id, product_id, NOW()
    FROM preference
    WHERE user_id = user1_id;

END LOOP;
CLOSE cur;