Normalisation

Question

Consider the following statements

1. Decomposition of a relation into BCNF may not be lossless.

2. If R and S are two relations in BCNF the natural join of R and S is also in BCNF.

which of the following is correct ?

a) only 1

b) only 2

c) Both 1 and 2

d) None of these

I have doubt in first option..please exlain..

Comments

@himgta

if you want you can have a loss-less decomposition always, but note that every decomposition of BCNF doesn't need not to satisfy Lossless property.

R(A,B,C,D) with FD set ={AB → D, C → AD}

i want to decompose it in R₁(A,B,D) R₂(A,C,D), it is in BCNF and Dependency Preservation but lossy

R₁(A,B,D) R₂(A,C,D), and R₃(B,C) ===> BCNF, DP and Loss-less

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@ Shaik Masthan but at least one decomposition of that relation into BCNF always be lossless ,not any particular given decomposition.

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@Prateek Raghuvanshi

yes brother, i am also conveyed that one only.