Last Updated :
30 Oct, 2018
Consider the following relation R(M N P Q) with functional dependencies:
FD = {MN → PQ, P → M, Q → N}
Which of the following is the correct set of candidate keys?
(A) 2
(B) 4
(C) 3
(D) 5
Answer: (B)
Explanation: Given FDs:
MN → PQ, P → M, Q → N
P → M
It can be replaced in MN → PQ
PN → PQ
[PN]+ → MNPQ
Q → N
Replace it
[PQ]+ → MNPQ
[MQ]+ → MNPQ
hence, there are 4 candidate keys.
Option (B) is correct.
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