The Relational Algebra

Abstract

Many relational queries can be formulated in terms of expressions whose operands represent relations and whose operators are the relational operations. Codd’s relational algebra is a high-level language in which questions can be put simply and succinctly /CODD 72/. Concepts from relational algebra have been incorporated into the design of several new database query languages, into view conceptions and into the conception of internal database schemata /IMLI 82/. Expressions in relational algebra manipulate tables of information by means of high-level operations such as select, project, and join. In section 2.1. an algebraic language is introduced. The underlying principle in algebraic languages is to consider the information we wanted to select can be expressed in relations obtained by successive application of database operators. In chapter 2.3, we consider the algebraic dependencies as an important application of the algebraic language.