GATE | GATE-CS-2015 (Set 3) | Question 65

Consider the relation X(P, Q, R, S, T, U) with the following set of functional dependencies

F = {
       {P, R} → {S,T},  
       {P, S, U} → {Q, R}
    }

Which of the following is the trivial functional dependency in F+ is closure of F?

(A) {P,R}→{S,T}
(B) {P,R}→{R,T}
(C) {P,S}→{S}
(D) {P,S,U}→{Q}


Answer: (C)

Explanation: A functional dependency X -> Y is trivial if Y is a subset of X.

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