Let's say I have table of cars and table of car manufacturers. Each car references one manufacturer.
Furthermore, each car that has manufacturer x requires an extra field. Say, cars from that manufacturer have an extra feature that needs configuring that no other manufacturer provides.
Where does this field go?
I think there should be another table with a one-one mapping between it and the cars table which holds the extra field for cars of that manufacturer.
So given this, how do I make sure that only cars of the correct type have this extra data in the other table? Or is this really bad data design?