Question

I come from frontend background, so I apologize if this db question seems dumb.

Say I have a database that handles orders of car and car accessories. If Car is non-customizable, then everything is easy-peasy. For every order, we simply need to associate the OrderId with the Car‘s ProductId. But a Car is a Product that can contain one or more Product like navigation, seat heater, etc. And users can also purchase those accessories Product separately.

How should we handle this best? Should every Product a user orders be given a unique ProductOrderId in the order table and if that Product can contain another Product, then we put it in a table that associates ProductOrderId with ProductId?

If we do this, would the db grow out of control? Seems a little inefficient to me. I have a feeling there is a better way.

Answer 1

If you look at how complex products are typically billed, the main item and each of its options are treated as separate line items in the bill of sale. In that kind of scenario, a car is a product and each of its accessories are also products. You can have an involuted relationship on product to indicate which accessories go with which type of car.

Your data model for this scenario would look something like this:

Alternatively, you could have a scenario where you want a level of abstraction such that your bill of sale contains only a single item, being a fully accessorized car. That requires the order item to become more like a header in a bill of materials, like so: