12 regras de Codd: diferenças entre revisões
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{{Em tradução|data=janeiro de 2012}}
As '''Doze regras de Codd''' são um conjunto de treze regras (enumeradas de zero à doze) propostas por [[Edgar F. Codd]], um pioneiro do [[modelo relacional]] para [[banco de dados]], designado para definir o que é necessário para que um [[sistema de gerenciamento de banco de dados]] para ser considerado ''relacional''.<ref>{{citation | last = Codd | first = Edgar Frank | title = Is Your DBMS Really Relational? | journal = ComputerWorld | date = 14 October 1985}}.</ref><ref>{{citation | last = Codd | first = Edgar Frank | title = Does Your DBMS Run By the Rules | journal = ComputerWorld | date = 21 October 1985}}.</ref> They are sometimes jokingly referred to as "Codd's Twelve Commandments".
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== As regras ==
'''Regra (0):''' O sistema precisa ser qualificado como ''[[Modelo relacional|relacional]]'', como um ''[[banco de dados]]'', e como um ''[[sistema de gerenciamento]]''.
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'''Regra 1:''' A ''regra da informação'':
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'''Regra 2:''' A ''regra de acesso garantido'':
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'''Regra 3:''' ''Tratamento sistemático de valores nulos:'':
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'''Regra 4:''' ''Active [[online]] [[Database catalog|catalog]] based on the relational model'':
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'''Regra 5:''' The ''comprehensive data sublanguage rule'':
:The system must support at least one relational language that
::# Has a [[linear syntax]]
::# Can be used both interactively and within application programs,
::# Supports data definition operations (including view definitions), data manipulation operations (update as well as retrieval), security and integrity constraints, and [[database transaction|transaction]] management operations (begin, commit, and rollback).
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'''Regra 10:''' ''Integrity independence'':
:[[Integrity constraints]] must be specified separately from application programs and stored in the
'''Regra 11:''' ''Distribution independence'':
:The distribution of portions of the database to various locations should be invisible to users of the database. Existing applications should continue to operate successfully
::# when a distributed version of the DBMS is first introduced; and
::# when existing distributed data are redistributed around the system.
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:If the system provides a low-level (record-at-a-time) interface, then that interface cannot be used to subvert the system, for example, bypassing a relational security or integrity constraint.
==
* [[Sistema R]].
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