GATE | GATE-CS-2005 | Question 30

Let r be a relation instance with schema R = (A, B, C, D). We define r₁ = Π_{A, B, C} (r) and r₂ = Π_A.D (r). Let s = r₁ * r₂ where * denotes natural join. Given that the decomposition of r into r₁ and r₂ is lossy, which one of the following is TRUE?
(A) s ⊂ r
(B) r ∪ s
(C) r ⊂ s
(D) r * s = s

Answer: (C)
Explanation: See Question 1 of https://www.geeksforgeeks.org/database-management-systems-set-10/amp/
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