Consider a schema R(A, B, C, D) and following functional dependencies.
Consider a schema R(A, B, C, D) and following functional dependencies.
A → B
B → C
C → D
D → B
Then decomposition of R into R1(A, B), R2(B, C) and R3 (B, D) is ______
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Correct answer: (A) Dependency preserving and lossless join
Explanation
A → B is preserved in R1, B → C in R2, and B → D, D → B in R3; C → D follows from C → B (in R2, since C → D → B) and B → D. So all dependencies are preserved. R1 ∩ R2 = B and R2 ∩ R3 = B, and B is a key of R2 and R3, so the decomposition is also lossless.