How to determine candidate keys from record schema and functional dependencies?

Question

If I have a schema say R={A,B,C,D} and functional dependencies say {B->C, D->A} will my set of candidate keys be {B,D} or {BD}?

Answer 1

If B were a candidate key, you'd have to be able to derive these functional dependencies from the ones given in the problem.

• {B->A}
• {B->C}
• {B->D}

Can you do that?