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Aug2016 cs Q10

0. Consider the table R with attributes A, B and C. The functional dependencies that hold on R are : A → B, C → AB. Which of the following statements is/are True ?
I. The decomposition of R into R1(C, A) and R2(A, B) is lossless.
II. The decomposition of R into R1(A, B) and R2(B, C) is lossy.

  • Option :
  • Explanation :
    Decomposition of R into R1(C, A) and R2(A, B) is lossless. Because C → A, A → B. So, C → AB can be derived and there is no loss. Decomposition of R into R1(A, B) and R2(B, C) is lossy. Because A → B, C → B are derived but we can't derive C → AB, So it is lossy. So, option (C) is correct.
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