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Relational Algebra
Once the relationships are identified, then operations that are applied on
the relations are also identified. In relational model, the operations are performed
with the help of relational algebra. Relational algebra is a collection of operations
on relations.
Each operation takes one or more relations as its operand(s) and produces another
relation as its result. We can compare relational algebra with traditional arithmetic
algebra.
In arithmetic algebra , there are operators that operate on operands( data
values) and produce some result. Similarly in relational algebra there are relational
operators that operate upon relations and produce relations as results.
Relational algebra can be divided into two groups:
1. Traditional set operators that
includes union, intersection, difference, and Cartesian product.
2. Special relational operators
that includes selection, projection, and division
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