An algebra of operations on database relations. Classical relational algebra has relational selection, relational projection, relational join, Cartesian product, union and relational difference; database aggregation requires an extension.
A relational algebra operation expressing a universal matching requirement. An explicit relational difference construction can specify the intended candidate universe, including the case of an empty divisor.
For two database relations with compatible database attributes, retains the database tuples in the first and absent from the second.
Combines database tuples satisfying a matching condition. A natural join uses equality of all shared database attribute names.
Retains the database tuples satisfying a condition.
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Relational algebra is a formal system for manipulating and querying relational data, which is organized into tables (or relations). It provides a set of operations that can be applied to these tables to retrieve, combine, and transform data in various ways. Relational algebra serves as the theoretical foundation for relational databases and query languages like SQL.