intersect (or intersection) is a relational operator that returns the intersection of two relation A and B, denoted by A ∩ B.
An intersection is defined as all tuples (rows) that are present in both of two union-compatible (same columns and same type) relation A and B.
The following definition are also equivalent.
A derived operator using minus (-) where the minus expression <math>( R1 - R2 )</math> returns anything that is only in R1
<MATH>\Large R1 \cap R2 = R1 - ( R1 - R2 ) </MATH>
<MATH> \Large R1 \cap R2 = R1 \times R2 </MATH>