Handling database table dependenciese

ms wrote:


thanks for reading this post. How do you handle dependencies? A really simple example: I've got a table called "entity" and another table, let's say, "entity_type". The entity types can be changed, of course, they also should be deletable, but only, if they are not used by some entities! How can I ensure this in Rails or directly in the DBMS (postgres)?

You need foreign key constraints in the database; check the Postgres docs for more details. I would *highly* recommend using the foreign_key_migrations plugin, which will manage these constraints automatically from your migrations (it's at harukizaemon (Simon Harris) ยท GitHub , along with a lot of other good stuff).

Big tip: always make your constraints deferrable. It will make testing *much* easier.

Do I have to check it manually within a validate-method in the model?

I suppose you could, but the DB will already do that if you have the constraints.