Q68

MCQ2 marks, −0.5

Let R and S be two relations with the following schema $R(\underline{P,Q}, R1, R2, R3)$ $S(\underline{P,Q}, S1, S2)$ where $\left\{P, Q\right\}$ is the key for both schemas. Which of the following queries are equivalent? Only I and II Only I and III Only I, II and III Only I, III and IV

(A)

$\Pi_P \left(R \bowtie S\right)$

(B)

$\Pi_P \left(R\right) \bowtie \Pi_P\left(S\right)$

(C)

$\Pi_P \left(\Pi_{P, Q} \left(R\right) \cap \Pi_{P,Q} \left(S\right) \right)$

(D)

$\Pi_P \left(\Pi_{P, Q} \left(R\right) - \left(\Pi_{P,Q} \left(R\right) - \Pi_{P,Q} \left(S\right)\right)\right)$

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