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 (σ (R)) = σ (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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