GATE | GATE MOCK 2017 | Question 31

A Relation R with FD set {A->BC, B->A, A->C, A->D, D->A}. How many candidate keys will be there in R?

(A) 1
(B) 2
(C) 3
(D) 4

Answer: (C)

Explanation: Simple candidate key means single attributed key. As (A)+ = {A, B, C, D}, (B)+ = {B,A, C, D}, (C)+ = {C} and (D)+ = {D, A, B, C}. So, A, B and D are candidate keys which are simple as well. So, correct option is 3.

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