GATE CSE 2002 | Question: 2.24

Question

Relation $R$ is decomposed using a set of functional dependencies, $F$, and relation $S$ is decomposed using another set of functional dependencies, $G$. One decomposition is definitely $\text{BCNF}$, the other is definitely $3NF$, but it is not known which is which. To make a guaranteed identification, which one of the following tests should be used on the decompositions? (Assume that the closures of $F$ and $G$ are available).

• A. Dependency-preservation
• B. Lossless-join
• C. $\text{BCNF}$ definition
• D. $3NF$ definition

Comments

Is C the right answer?

As BCNF means it's already in 3NF but not the vice-versa

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This is because the relation whose highest normal form is 3NF will fail the BCNF test, but both will pass the 3NF test.

 

Answer 1

Explain please

3NF Dependency always preserved but in BCNF it  may or may not be preserved.