Good day first, some doubts arose when I was developing the database of my online sales site (only for context of classes ...). This is the following, I have the products table, then I have the cart, invoice and orders, all I have to save the products, just add another field in them where I save the product code? or how do we have another table linking them by having a many-to-many relationship works the other way? , I'm kind of confused ... whelp