UGC-NET | UGC NET CS 2016 July – III | Question 10

Which of the following statements is TRUE?
D₁ : The decomposition of the schema R(A, B, C) into R₁(A, B) and R₂ (A, C) is always lossless.
D₂ : The decomposition of the schema R(A, B, C, D, E) having AD → B, C → DE, B → AE and AE → C, into R₁ (A, B, D) and R₂ (A, C, D, E) is lossless.
(A) Both D₁ and D₂
(B) Neither D₁ nor D₂
(C) Only D₁
(D) Only D₂


Answer: (D)

Explanation: Only D2 is True because AD is key and present in both the tables.
D1 is not always true because FD’s not given and if we take B->A and C->A then it is lossy decomposition because no common attributes contain key from one of the table.


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