How to design a sales database correctly?

Question

Database design

Tell me how to properly design a database structure for selling various goods and services. At the same time, goods and services should be included in the tariff. That is, not a separate product will be bought, but a tariff that will consist of various products. I don’t understand how to link the products table directly with the products themselves, because they can be in several tables. For example, some data sets, this will be the first table, and various site functionality, this will be the second table. And here's how to add tariffs to the table, two products from different tables?

Answer 1

Google Many-to-Many Polymorphic Relationship