4,732 views

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

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 $B = 20).$

Could we have in option 'a' in place of or operator and operator

then both a and c will be correct option.