Question

Which of the following relation schema with given functional dependency follows 3NF but not BCNF?

Answer 1

(c)
$\bullet$ Option (a) has partial dependency i.e., D $\to$ E hence not in 2 NF
$\bullet$ Option (b) has partial dependency i.e., B $\to$ D and B $\to$ C hence not in 2 NF
$\bullet$ Option (c) is in 3NF but not in BCNF because functional dependancy D $\to$ A is not a super key.
$\bullet$ Option (d) is not in 3NF because of transitive dependency A $\to$ B and B $\to$ C. But relation is in BCNF every functional dependency has a super key.