Consider a relation schema R = (U, V, W, X, Y, Z), on which the following functional dependencies hold: {U → V, VW → X, Y → W, X → U}. The candidate keys of R are:
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Correct answer: D. UYZ, VYZ, XYZ
Explanation
Y and Z never appear on a right side, so both are in every key; (YZ)⁺ = {Y, Z, W}. Adding U gives V, then VW → X, so UYZ is a key. VYZ gives X then U, and XYZ gives U then V. WYZ adds nothing new. Keys: UYZ, VYZ, XYZ.More Database Management Systems questions
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