I'm not sure I fully understand the question. It's like asking why a numeric field cannot accept characters.

If table1 has a PK Col1, Col2 - Table2 cannot have an FK to only Col2. It wouldn't make any sense to do that. I'm not sure what you would expect it to do, but it is not allowed because it would simply be wrong.

An FK must point to the entire PK - that's the law

Why is the PK of BR_Header composite anyway? It would seem as if BR_No would be unique for the receipt, no?

- Chris