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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
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
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It defines that the tuple in one relation that refers to another relation must refer to an existing tuple in that relation. This constraint is states on two relations (not essentia
write on the various type of relationalkey
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