Comment by nonethewiser

What would be the advantage of implementing it in the application?

I only see disadvantages:

- no data integrity check in the database

- more complicated definition of foreign relation, or none at all, leaving possibility for deviant data

- scatteted schema. Cant look at the db table and understand the entire model. Have to hunt in code an potentially across a lot of code.

It just seems like a data integrity issue that needs to be enforced at the db level.