Relation R, with associated set of functional dependencies F, is decomposed…
2002
Relation R, with associated set of functional dependencies F, is decomposed into BCNF. The redundancy (arising out of functional dependencies) in the resulting set of relations is:
- A.
Zero
- B.
More than zero but less than that of an equivalent 3NF decomposition
- C.
Proportional to the size of F⁺
- D.
Indeterminate
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Correct answer: A
The correct answer is Option A. A relation is in BCNF if, for every non-trivial functional dependency X → Y that holds in the relation, X is a superkey. This condition removes redundancy that arises because of functional dependencies inside the resulting relations. A BCNF decomposition may fail to preserve all dependencies, but the FD-based redundancy in each resulting BCNF relation is zero. Therefore, the redundancy arising out of functional dependencies in the resulting set of relations is zero.