Intersection, Database Management System

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

A

B

A1

B1

A2

B2

A4

B4

 

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

Posted Date: 3/6/2013 5:45:16 AM | Location : United States







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