Consider a relation R(A,B,C,D,E) holds FDs. F ={AB->C, C->D, B->E} is…
Consider a relation R(A,B,C,D,E) holds FDs. F ={AB->C, C->D, B->E} is decomposed into R1(A,B,C) and R2(C,D) then which of the following are false about this decomposition?
Answer: A. Lossless and dependency preserving; B. Dependency preserving and Not lossless; C. Lossless and Not dependency preserving — (a) (b) (c) R1R2≠R, hence lossy join decomposition Attribute E is not present in R1∪R2 B->E is lost so not dependency preserving.
- A.
Lossless and dependency preserving
- B.
Dependency preserving and Not lossless
- C.
Lossless and Not dependency preserving
- D.
Not dependency preserving and lossy
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Correct answer: A, B, C
(a) (b) (c)
R1R2≠R, hence lossy join decomposition
Attribute E is not present in R1∪R2
B->E is lost so not dependency preserving.