Container Managed Relations

[Maximilian Trenks]

Hello,
I didn't find a good explanation on CMR.
Lets say I have a Table A which references table B. So I could make a table C with primkey of A and primkey of B as attributes.
But is this necessary ? Do i have to create a table and thus an entity bean ?
Or it it possible to just define the relationship as C and use this relation as if a real database table exists ?
Please help me to bring light in this matter.(does this phrase actually exist ?)
Max