Relation (database)

The number of attributes constituting a heading is called the degree, which term also applies to tuples and relations.

[4] Thus, an n-ary relation is interpreted, under the Closed-World Assumption, as the extension of some n-adic predicate: all and only those n-tuples whose values, substituted for corresponding free variables in the predicate, yield propositions that hold true, appear in the relation.

In SQL, a database language for relational databases, relations are represented by tables, where each row of a table represents a single tuple, and where the values of each attribute form a column.

A similar comment does not apply here to SQL, which does define an ordering to the columns of a table.

An update to a single relvar causes the body of the relation assigned to that variable to be replaced by a different set of tuples.

By using a Data Definition Language (DDL), it is able to define base relation variables.

The Data Definition Language (DDL) is also used to define derived relation variables.

In SQL, CREATE VIEW syntax is used to define a derived relation variable.