1.

Let r be a relation instance with schema R = (A, B, C, D). We define r1 = ΠA, B, C (r) and r2 = ΠA.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» D. r * s = s


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