Do link tables need a meaningless primary key field?

Question

I am working on a couple of link tables and I got to thinking (Danger Will Robinson, Danger) what are the possible structures of a link table and what are their pro\'s and c

Answer 1

I have used composite key to prevent duplicate entry and let the database handle the exception. With a single key, you are rely on the front-end application to check the database for duplicate before adding a new record.