Relational algebra

The relational algebra is a set of operations that

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manipulate relations as they are defined in the relational model and as such describes part of the data manipulation aspect

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of this data model. Because of their algebraic properties

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these operations are often used in database query optimization

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as an intermediate representation of a query to which certain

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rewrite rules can be applied to obtain a more efficient version of

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the query.

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The exact set of operations may differ per definition and also

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depends on whether the unlabeled relational model (that uses mathematical relations) or the labeled relational model (that uses

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the labeled generalization of mathematical relations) is used. We

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will assume the labeled case here as this is the most common way

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the relational model is defined. That means that we assume that

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tuples are partial functions from

Related Topics:
Tuple - Function

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attribute names to values. The attribute a of a tuple t is

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denoted in this article as t(a).

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