随机连接3个表中的记录

Question

I have three tables:

categories (id)
product_models(id, category_id)
products(id, product_id, category_id)

There are records on each table (lorem ipsum content), i want to connect the data.
I've changed already the product_models, executing this query:

    update product_models
    set category_id = (select id from categories order by RAND() limit 1)

How can I use a single query that will map all the products to a product model and update the category also?

Answer 1

您应该根据需要添加对表的约束和引用，以便在更新一个表时，其他表也将更新。

Answer 2

Assuming that your third table structure is (id, product_model_id, category_id), another assumption is that you have a composite foreign key (product_model_id, category_id), then you have to update the third table like below

UPDATE products P
INNER JOIN (SELECT id, category_id from product_models ) M
ON P.product_id = M.id
SET P.category_id = M.category_id