Re: WWW/Internet 2009: 2nd CFP until 21 September

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Fri, 14 Aug 2009 10:49:43 -0300
Message-ID: <4a856b78$0$23747$9a566e8b_at_news.aliant.net>



paul c wrote:

> Mr. Scott wrote:
>

>> ...
>>
>>> 1) in SQL, just what does decompositon of tables mean?  Does it mean 
>>> what relational decomposition means, ie., lossless  projection, or 
>>> something else?
>>
>>
>> Relational decomposition doesn't mean lossless projection.  The 
>> decomposed relations can contain extra tuples that don't show up in a 
>> join. Referential constraints are needed to prevent the extra tuples.
>> ,,,

>
> What is the difference between 'relational decomposition' and mere
> projection?

Basically, he's making shit up as he goes along. There are any number of ways of decomposing relations. Lossless decomposition by projection/join is the basis for normalization, but that's by no means the only way to decompose relations. For example, another obvious way to decompose relations is by restrict/union. Received on Fri Aug 14 2009 - 08:49:43 CDT

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