Normal forms,DBMS

Question

Consider relation R with set functional dependencies (F) as: $R(ABCD)$ and

$F \left \{  AB \rightarrow  CD, C \rightarrow A, A \rightarrow C \right \}$.
 1) If the above relation is decomposed into R1 (CBD), R2 (CA) then the relation is in

(A) INF but not in 2NF

(B) 2NF but not in 3NF

(C) 3NF but not in BCNF

(D) BCNF

2)The above decomposition is

(A) Lossless and also dependency preserving

(B) Lossy but dependency preserving

(C) Lossy and also dependencies are not preserved

(D) Lossless but dependencies are not preserved

Comments

@Bhavna

what is the problem you are facing, while solving this questions?

Answer 1

It is bcnf

Loseless but not dependency preserving

Comments

Yes i thought so too but given ans is loosless n dp.

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Yes it is dependency preserving too

 

AB and CB are candidate keys of the relation

So AB-> CD

BC->AD

 

When you decompose the relation

(CBD)

BC-> D

 

(CA)

C->A

A->C

If you take F+ You will get all functional dependency

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@Priyanka Agarwal

how it is in BCNF? Please explain.

And what is the functional dependency contain in Relation R1(C B D)?