# relational algebra

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## relational algebra

(database, theory)
A family of algebra with a well-founded semantics used for modelling the data stored in relational databases, and defining queries on it. The main operations of the relational algebra are the set operations (such as union, intersection, and cartesian product), selection (keeping only some lines of a table) and the projection (keeping only some columns).

The relational data model describes how the data is structured.

Codd's reduction algorithm can convert from relational calculus to relational algebra.

## relational algebra

(1) The branch of mathematics that deals with relations; for example, AND, OR, NOT, IS and CONTAINS.

(2) In a relational database, a collection of rules for dealing with tables; for example, JOIN, UNION and INTERSECT.
References in periodicals archive ?
In the first step, the relational algebra is extended with new operators that execute the most expensive processes of association and classification tasks.
Operations of relational algebra include the followings: Union, Intersect, Set Difference, Cartesian Product (operations based on set theory) and Select, Project, Join, Division (are operations developed especially for relational databases).
In this section we consider a more specific framework of update methods implemented in the relational algebra, inspired by the algebraic model of object-oriented database access introduced by Hull and Su [1989].
Since the relational algebra and calculus are equivalent to pure first-order logic, they have [AC.
So any expression in our probabilistic relational algebra yields a probabilistic relation.
In this case, our selection is based on the classical relational algebra.
We present a relational algebra and a tuple calculus for our model and prove their equivalence.
OQL queries in our framework are translated into a calculus format that serves as an intermediate form, and then are translated into a version of the nested relational algebra.
Extending Relational Algebra and Relational Calculus with
This mapping assumes a mapping of SQL-92 to relational algebra and defines temporal statements in terms of their mapping to well-defined temporal and conventional relational algebra expressions.
MATCH is a new operator for relational algebra which provides a natural and nonprocedural means to express retrievals based on very complex patterns which are themselves stored as data.
The algorithm uses an extension of relational algebra to model rule conditions and actions.

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