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

From: paul c <>
Date: Thu, 13 Aug 2009 02:00:16 GMT
Message-ID: <QsKgm.38900$Db2.18218_at_edtnps83>

Mr. Scott wrote:
> "paul c" <> wrote in message
> news:IYAgm.40873$PH1.30537_at_edtnps82...
>> Mr. Scott wrote:
>> ...
>>> I'm confused.  What requirement are you referring to?  Are you referring 
>>> to the requirement that nulls be eliminated or the fact that an order 
>>> isn't an order without a delivery destination?  The referential cycle was 
>>> a consequence of trying to eliminate nulls. ...
>> I meant the requirement that a delivery address can't be recorded without 
>> an order date.

> I'm even more confused.

Okay, I'll give it a try. My ignorance of the 1000-page-or-so sql standard puts me at a disadvantage, so to quote one of your earlier posts: "If the table is decomposed into tables (X), (X,A), (X,B) and (X,C)", I have to ask a few questions.

  1. in SQL, just what does decompositon of tables mean? Does it mean what relational decomposition means, ie., lossless projection, or something else?
  2. (allow me to drop the parenthesis and use braces, just because it makes me happier to avoid any nuance of implementation language) Does the relation {X,A,B,C} have one predicate or several?
  3. If the answer to 2) is 'several predicates', is this because a disjunction is involved or because nulls are involved and what are those predicates?
  4. if the answer to 2) is 'one predicate', what does projection on any of the four columns mean?
Received on Wed Aug 12 2009 - 21:00:16 CDT

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