GATE1998-1.33

Question

Given two union compatible relations $R_1(A, B)$ and $R_2 (C, D)$, what is the result of the operation $R_1 \Join_{ A = C \wedge B = D} R_2$?

• A. $R_1 \cup R_2$

• B. $R_1 \times R_2$

• C. $R_1 – R_2$

• D. $R_1 \cap R_2$

Comments

Please explain

Answer 1

This question is an example of Theta Join,

 

The join here will be selecting only those tuples where A = C and B = D, meaning it is the intersection. D option.