Question

I’ve a relationship table for my many-to-many entities.

author_id | book_id

Do I need to add relation_id? I should be able to identify using both id.

Thank you

Answer 1

Since you’re using Doctrine, try not to think too much on the RDBMS level (at least, not most of the time).

If you have two Entities with a ManyToMany relationship, you should forget about the surrogate key. In fact, you should pretty much ignore the fact that the relationship table exists. You simply have two related entity types.

Now, if you need to store metadata about the relationship itself (for instance the date a badge was awarded to a user), you’re going beyond a simple ManyToMany, and you need to model that relationship yourself — by creating a new kind of entity (a UserBadge, for instance). That entity, of course, would have an id.

You’re using an ORM, think about entities, not about tables (most of the time)!