I have the following scenario:

Table A:
id (primary)
activityid (not officially primary but still is unique)

Table B:
....
activityid

activityid in B is a foreign key.

class A has an association of B's (one to many).
but when i try to create a one-to-many collection from A to B (in A.hbm), i can only specify the foreign key in B, and NHibernate automatically makes a join using the primary of A which is 'id', with the specified foreign key of B.
that's no good for me...

can i do it differently with out changing the DB?

Thanks :)