Division operation, Database Management System

To do the division operation R1 ÷ R2, R2 should be a correct subset of R1. In the following example R1 have attributes A and B and R2 have only attribute B so R2 is a correct subset of R1. If we perform R1 ÷ R2 than the resultant relation will have those values of A from R1 that are related to all values of B present in R2.

Example

A

B

A1

B1

A1

B2

A2

B1

A3

B1

A4

B2

A5

B1

A3

B2

Let R1

If R2                    R3= R1 ÷ R2                      If R2                       R3= R1 ÷ R2

180_DIVISION operation.png

If R2                  R3= R1 ÷ R2                                               If R2             R3= R1 ÷ R2

1567_DIVISION operation1.png

Figure:  The Division Operation

Note:

               Degree of relation: Degree (R ÷ S)=Degree of R - Degree of S.

Posted Date: 3/6/2013 5:57:47 AM | Location : United States







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