Relational model concepts

A relational model is a first-order predicate logic, which was first introduced by Edgar F. Codd in 1970 in his paper A relational model of data for large shared data banks. A database is represented as a collection of relations. The state of the whole database is defined by the state of all the relations in the database. Different information can be extracted from the relations by joining and aggregating data from different relations and by applying filters on the data. In this section, the basic concepts of the relational model are introduced using the top-down approach by first describing the relation, tuple, attribute, and domain.

The terms relation, tuple, attribute, and unknown, which are used in the formal relational model, are equivalent to table, row, column, and null in the SQL language.