MySQL表多个外键

Question

I have three table users, cars and enquiries and their design is like:
users:
id ,name, email
cars:
id,user_id,name
Enquiry:
id, car_id,description

I just want to know that should I have to keep user_id in Enquiry table or not.As I know that i can fetch user detail with reference of car_id of cars table.what is the best way to manage these kind of things. Thanks in advance.

Answer 1

If you remove the user_id from Enquiry table, you have an implicit assumption in your design that the enquiry is aways created by the car owner.

Is this assumption acceptable to you?

This may be very subjective, but talking about correctness, my opinion is that you should keep the user_id because Enquiry itself is an entity and should have its own owner.

Answer 2

它基于您的报告，但是我想说，您将不需要额外的user_id，因为每次您要参加所有表时都会使用“查询”来详细说明用户信息和汽车信息。