In database theory, relational algebra is a theory that uses algebraic structures for modeling data, and defining queries on it with well founded semantics...

In relational algebra, a projection is a unary operation written as Π a 1 , . . . , a n ( R ) {\displaystyle \Pi _{a_{1},...,a_{n}}(R)} , where R {\displaystyle...

In relational algebra, a selection (sometimes called a restriction in reference to E.F. Codd's 1970 paper and not, contrary to a popular belief, to avoid...

database. The relational calculus is similar to the relational algebra, which is also part of the relational model: While the relational calculus is meant...

In relational algebra, a rename is a unary operation written as ρ a / b ( R ) {\displaystyle \rho _{a/b}(R)} where: R is a relation a and b are attribute...

A relational database (RDB) is a database based on the relational model of data, as proposed by E. F. Codd in 1970. A database management system used...

The relational model (RM) is an approach to managing data using a structure and language consistent with first-order predicate logic, first described in...

directed graphs, where objects reference each other. Relational is tuples in tables with relational algebra. Tuples are data fields grouped into a "row" with...

(sigma algebra), a refinement of sigma algebras Join (algebraic geometry), a union of lines between two varieties In computing: Join (relational algebra),...

= { x ∈ X : x ∼ a } . {\displaystyle [a]=\{x\in X:x\sim a\}.} In relational algebra, if R ⊆ X × Y {\displaystyle R\subseteq X\times Y} and S ⊆ Y × Z {\displaystyle...