Let R(A, B, C, D) be a relational schema with functional dependencies A → B, B → C, C → D and D → B. The decomposition of R into (A, B), (B, C), (B, D)
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Correct answer: A. gives a lossless join, and is dependency preserving
Explanation
B, C, D determine one another (B → C → D → B). Each join is on B, which is a key of (B, C) and (B, D), so the join is lossless. A → B is in (A, B), B ↔ C is in (B, C), B ↔ D is in (B, D), and C → D follows from C → B → D, so all FDs are preserved.More Database Management Systems questions
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