made easy dbms tt1

Question

Which of the following query transformations (i.e., replacing the l.h.s. expression by the r.h.s expression) is correct? R1, R2 and R3 are relations, C1 and C2 are selection conditions and A1 ,A2 and A3 are attributes of Relations

 

SHOULDN’T THE ANSWER BE (B)???

OPTION (D) IS FALSE ON THIS EXAMPLE:-

R1

A1	A2
1	2
1	3
2	4
2	5
3	8

 

R2

A1	A2
1	2
2	5
3	8

 

NOW OPTION D’s LHS GIVES $\phi$ WHEN I USE condition A1 as A1<3 and condition A2 as  A2<8 

whereas RHS gives me 

A1

1

1

2

2

hence option D is wrong?

 

 

Comments

b should be correct right???anyone??

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Even i think b is correct option. They have asked for correct/valid expressions and d is invalid.