Example of relational operations, Database Management System

Consider the relation PERSON. If you want to display details of persons having age less than or equal to 30 than the select operation will be used as follows:

σ AGE <=30 (PERSON)

The resultant relation will be as shown:

PERSON_ID

NAME

AGE

ADDRESS

2

Sharad Gupta

30

Pocket 2, Mayur

Vihar.

 

 

 

Note:

1)   Select operation is commutative; i.e.,

σ (R)) = σ (R))

Therefore, series of select can be applied in any order

2) More than one condition can be applied using Boolean operators OR & AND etc.

Posted Date: 3/6/2013 5:50:22 AM | Location : United States







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