Multiple choice

Consider a relation scheme R = (A, B, C, D, E, H), on which the following functional dependencies hold: (A ® B, BC ® D, E ® C, D ® A). What are the candidate keys of R?

  1. AE, BE

  2. AE, BE, DE

  3. AEH, BEH, BCH

  4. AEH, BEH, DEH

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

To find candidate keys, calculate the closure of sets containing E and H (since they do not appear on the right side of any FD). Closure(AEH) = {A, E, H, B, C, D} = R. Closure(BEH) = {B, E, H, C, D, A} = R. Closure(DEH) = {D, E, H, A, B, C} = R. Thus, AEH, BEH, and DEH are candidate keys.