If R1 and R2 are two union compatible relations or functions, then the result of R3 = R1 ∩R2 is the relation that contains all tuples that are in both the relations In other words, R3will have tuples such that R3 = {t | R1 ∋ t ∧ R2 ∋ t}.
Example:
R1
|
A
|
B
|
|
A1
|
B1
|
|
A2
|
B2
|
|
A3
|
B3
|
|
A4
|
B4
|
R2
|
A7
|
B7
|
|
X
|
Y
|
|
A1
|
B1
|
|
A7
|
B7
|
|
A2
|
B2
|
|
A4
|
B4
|
|
R3 = R1 ∩ R2 is
|
|
R3 = R1 ∩ R2 is
Note: 1) Intersection is an associative operation, i.e., R1 ∩ (R2 ∩ R3) = (R1 ∩ R2) ∩ R3
2) Intersection is a commutative operation, i.e., R1 ∩ R2 = R2 ∩ R1