Many to Many Relation Design - Intersection Table Design

Question

I\'m wondering what a better design is for the intersection table for a many-to-many relationship.

The two approaches I am considering are:

CREATE TA         


        

Answer 1

Benefits of the first one:

The ability to look up the join table by a single value. This makes some look up operations simpler on the client side.

Some ORMs (NHibernate) also require ids in each entity for persistence to work properly.

Benefits of the second one:

Simpler data model, with no need to create the additional index.

Less memory required.