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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