Tuple - Relational Model

Relational Model

In database theory, the relational model uses a tuple definition similar to tuples form functions, but each tuple element is identified by a distinct name, named an attribute, instead of a number; this leads to a more user-friendly and practical notation, A tuple in the relational model is formally defined a finite function that maps attributes to values. For example:

(player : "Harry", score : 25)

In this notation, attribute–value pairs may appear in any order. The distinction between tuples in the relational model and those in set theory is only superficial; the above example can be considered a 2-tuple if an arbitrary total order is imposed on the attributes (e.g. ) and then the elements are distinguished by this ordering rather than by the attributes themselves. Conversely, a 2-tuple may be considered a relational model tuple over the attributes .

In the relational model, a relation is a (possibly empty) finite set of tuples all having the same finite set of attributes. This set of attributes is rather formally called the sort of the relation, and rather casually called the set of column names. A usually implementation of a Tuple is a row in a database table, yet see relational algebra for means of deriving tuples not physically represented in a table.