I have a table that stores a user ID and a subscription type, and this is really all it needs to store and any pair of values will always be unique. In fact, I think this pair should be the primary key on the table. However, I'm using Castle ActiveRecord which says at:
Quick Note: Composite keys are highly discouraged. Use only when you have no other alternative.
I get the feeling they're discouraged from a SQL point of view, but it doesn't actually say why anywhere. Is there any good reason to avoid using composite keys on a table? Why waste the space of an extra key if you don't have to? Thanks!
