Q21

MCQ1 mark, −0.33

What is the optimized version of the relation algebra expression $\pi_{A1}(\pi_{A2}(\sigma_{F1}(\sigma_{F2}(r))))$ , where $A1, A2$ are sets of attributes in $r$ with $A1 \subset A2$ and $F1,F2$ are Boolean expressions based on the attributes in $r$ ?

(A)

$\pi_{A1}(\sigma_{(F1 \wedge F2)}(r))$

(B)

$\pi_{A1}(\sigma_{(F1 \vee F2)}(r))$

(C)

$\pi_{A2}(\sigma_{(F1 \wedge F2)}(r))$

(D)

$\pi_{A2}(\sigma_{(F1 \vee F2)}(r))$

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