Consider a schema R(A,B,C,D) and functional dependencies A→B and C→D. Then the…
2001
Consider a schema R(A,B,C,D) and functional dependencies A→B and C→D. Then the decomposition of R into R₁(AB) and R₂(CD) is
Answer: C. dependency preserving but not lossless join — The functional dependencies A→B and C→D are preserved in R₁(AB) and R₂(CD) respectively. However, the intersection of attributes between R₁ and R₂ is empty,…
- A.
dependency preserving and lossless join
- B.
lossless join but not dependency preserving
- C.
dependency preserving but not lossless join
- D.
not dependency preserving and not lossless join
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Correct answer: C
The functional dependencies A→B and C→D are preserved in R₁(AB) and R₂(CD) respectively. However, the intersection of attributes between R₁ and R₂ is empty, which violates the lossless join condition. Thus, this decomposition is dependency preserving but not lossless join.
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