Question-6

Consider the relation student shown in the below table:

Roll_no	Name	marks
1	Ram	50
2	Rakesh	65
3	Ram	45
4	Pranav	89
5	Rakesh	99
6	Emily	99
7	Grace	100
8	Lily	95

What is the number of tuples returned by the following relational algebra expression: \(\prod_{\text{name}}(\sigma_{\text{marks}>50}(\text{student}))\)?

Answer

\(5\)

Solution

Relational algebra, based on set theory, returns unique tuples. The query retrieves tuples where the ‘marks’ are greater than \(50\) and projects only the ‘name’ attribute. The repeated entries, like ‘Rakesh’, will be returned only once. Hence, only \(5\) tuples are returned.

Name
Rakesh
Pranav
Emily
Grace
Lily