Adding fields from a logically related entity?

Question

I have two entities (A and B) which share a common key, but aren't related by primary/foreign key in the database. I have created a logical relationship between the two in the data source view, and a matching role in a model. The cardinality of the role is "OptionalMany to OptionalMany" since none of the columns are marked as unique in the DB.

My problem is that if I try to create a report where I use a field from entity A, then the other entity shows up in the list of entities, but I can't drop any of its fields into the report. Any suggestions on what might be missing? I have trawled through the online books, but with no success :(

Answer 1

I accidentally discovered the solution. Changing the cardinality to One or OptionalOne in one end of the relation made the problem go away.