Virtual Gate Test Series:Databases-Normalization-Functional dependency

Question

A relation $R(ABCDEFGHIJ)$ with functional dependency set

$F={AB\rightarrow C , A\rightarrow DE , B\rightarrow F , F\rightarrow GH, D\rightarrow I J}$ , and the decomposition of $R$ is

${R1(ABCD) , R2(DE) ,R3(BF),R4(FGH),R5(DIJ)}.$

Which of the following is/are true?

$1.$lossless

$2.$lossy

$3.$Not dependency preserving

$4.$Dependency preserving

Comments

It is not dependency preserving......A-->DE is not preserved....check again!

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yeah thanks i calculated wrong closure. its not dependency preserving as A->E is not preserved.

A->D is preserved in R1

Answer 1

A->DE FD is not satisfied in any Relation so it is not dependency preserving

In R2(DE) D is not a key attribute so when combined with other relations it gives a lossy

 

So  2.lossy

3.Not dependency preserving are true

Comments

Yes I also thought so but the answer says lossless and dependency preserving

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A->DE you can write it A->D which we can combine in R1(ABCD)

NOW A->E doesn't combine  in R2(DE) so not dependency preserving and lossy join

Answer 2

Not dependency preserving as  A->DE is not preserved

lossy as  in R2(DE) D is not CK

 

 

2,3 are correct