APPENDIX ACodd's 12 Rules for an RDBMS

Although most of us think that any database that supports SQL is automatically considered a relational database, this isn't always the case—at least not completely. In Chapter 1, I discussed the basics and foundations of relational theory, but no discussion on this subject would be complete without looking at the rules that were formulated in 1985 in a two-part article published by Computerworld magazine ("Is Your DBMS Really Relational?" and "Does Your DBMS Run By the Rules?" by E. F. Codd, Computerworld, October 14 and October 21, 1985). Many websites also outline these rules. These rules go beyond relational theory and defines more specific criteria that need to be met in an RDBMS, if it's to be truly ...

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