The model, first proposed by Codd in 1969 and used exclusively in the context of database management systems, takes its name from an analogy that can be drawn between a table as described and the mathematical concept of a relation. In this analogy table corresponds to relation, row (in a table) to tuple (of a relation), and the column names (of the table) to the domain ordering (in the relation). Using this analogy Codd developed various sets of operations on which languages for the manipulation of such tables might be based and from which the now widely used data sublanguage SQL is derived.
In spite of its name, which can be a source of confusion, the model makes no provision for maintaining relationships between rows in different tables and the only constraint on the rows within a particular table is that no two rows are identical. Each row, from the viewpoint of the model, is thus an independent entity. It can only be related to other rows by correspondences between contained data items, which is a matter for the user.
See also normal forms, foreign key, ERA model.
"relational model." A Dictionary of Computing. . Encyclopedia.com. (August 18, 2018). http://www.encyclopedia.com/computing/dictionaries-thesauruses-pictures-and-press-releases/relational-model
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