Suppose R1(A, B) and R2(C, D) are two relation schemas. Let r1 and r2 be the…

GATE · 2012 · CS · Computer Science & IT

1. A.

   $\Pi_{B}(r_{1})- \Pi_{C}(r_{2})= \varnothing$

2. B.

   $\Pi_{C}(r_{2})- \Pi_{B}(r_{1})= \varnothing$

3. C.

   $\Pi_{B}(r_{1}) = \Pi_{C}(r_{2})$

4. D.

   $\Pi_{B}(r_{1}) - \Pi_{C}(r_{2}) \neq \varnothing$

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