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 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) BCNF definition
(D) 3NF definition
Answer: (C)
Explanation: Answer is (C) since to identify BCNF we need BCNF definition. One relation which satisfies will be in BCNF and other will be in 3NF.
1st is wrong because dependency may be preserved by both 3NF and BCNF.
2nd is wrong Because both 3NF and BCNF decomposition can be lossless.
4th is wrong because 3NF and BCNF both are in 3NF also.
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