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Message Posted: Fri, 27 Jul 2012 @ 13:45:32 GMT


     
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Subj:   Re: Codd's rules in teradata
 
From:   Dieter Noeth

sughesh iyyani wrote:

  We know Teradata satisfies 11.5 or 12 codd rules.  


I don't ;-)

At least i don't know how many are satisfied by Teradata, but i would expect less than that.


  Kindly let me know what is meant by Codd rule?  


en.wikipedia.org/...


A quick check shows at least two broken rules:

Rule 2: The guaranteed access rule -> broken by MULTISET tables

Rule 6: The view updating rule -> only very basic views can be updated


Most RDBMSes break those rules, too.


  If a RDBMS satisfies 12 codd rules, what exactly meant by that?  


It's a fully relational DBMS according to Codd's Relational Model.

Some people argue that none of the existing RDBMSes are truly relational based on flaws in implementations and SQL:

www.dbdebunk.com

www.thethirdmanifesto.com/


Of course they're right, but until there's a "real" RDBMS we have to work with existig implementations :-)


Dieter



     
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