Consider R(A, B, C, D, E) be a relation with the following dependencies: C → F, E → A, EC → D, A → B. Which of the following is a key for R?
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Correct answer: B. EC
Explanation
E and C never appear on the right side, so every key must contain both. (EC)⁺ = {E, C, A (E→A), D (EC→D), B (A→B)} = all attributes of R. So EC is the key.More Database Management Systems questions
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