The Project Operation
The project
operation helps to filter out some of the attributes of a relation. In other
words we can select part of the attributes of a relation using project
operation. Projection is denoted by the uppercase Greek letter pi (Π). We list
those attributes of a relation we wish to appear in the result as a subscript
to Π. The relation appears in parenthesis after the projection.
If we wish to
list all loan numbers and amount of the loans for the loan relation, we write:
Consider the
more complicated query “Find those customers who live in Dhaka city”. We write:
This query is a
composition of the relational operations of both select and projection.
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