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+15 votes

The relational algebra expression equivalent to the following tuple calculus expression:

$\left\{t \mid t \in r \land \left(t[A] = 10 \land t[B]=20\right)\right\}$ is

  1. $\sigma_{(A=10 \lor B=20)} (r)$

  2. $\sigma_{(A=10)} (r) \cup \sigma_{(B=20)} (r)$

  3. $\sigma_{(A=10)} (r) \cap \sigma_{(B=20)} (r)$

  4. $\sigma_{(A=10)} (r) - \sigma_{(B=20)} (r)$

asked in Databases by Veteran (59.6k points)
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1 Answer

+16 votes
Best answer
Answer: C

Tuple t should have two attributes A and B such that t.A = 10 and t.B = 20.

So, (Tuples having A = 10) $\cap$ (Tuples having B = 20) = (Tuples having A = 10 and B = 20).
answered by Boss (34k points)
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