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Question 29Asked in UGC NET Computer Science, June 2017 (Paper II & III, Selected Questions)

Consider a schema R(MNPQ) and functional dependencies M → N, P → Q. Then the decomposition of R into R₁ (MN) and R₂(PQ) is ______

  1. ADependency preserving but not lossless join
  2. BDependency preserving and lossless join
  3. CLossless join but not dependency preserving
  4. DNeither dependency preserving nor lossless join
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Correct answer: (A) Dependency preserving but not lossless join

Explanation

With R(MNPQ), M → N and P → Q, the decomposition into R₁(MN) and R₂(PQ) clearly preserves both dependencies, but it is not lossless because R₁ and R₂ have no common attribute, so R cannot be recovered by joining them.

From UGC NET Computer Science PYQ, June 2017 (Paper II & III, Selected Questions)

This is question 29 of UGC NET Computer Science PYQ, June 2017 (Paper II & III, Selected Questions). See all questions of this paper with answers, or attempt the paper as a timed online test to get your score and all-India rank.