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

  1. $R_1 \cup R_2$

  2. $R_1 \times R_2$

  3. $R_1 – R_2$

  4. $R_1 \cap R_2$

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This question is an example of Theta Join,

$r \bowtie_\theta s= \sigma_\theta(r \times s)$

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

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