Path: text.usenetserver.com!out04b.usenetserver.com!news.usenetserver.com!in02.usenetserver.com!news.usenetserver.com!postnews.google.com!f36g2000hsa.googlegroups.com!not-for-mail
From: JOG <jog@cs.nott.ac.uk>
Newsgroups: comp.databases.theory
Subject: Re: Examples of SQL anomalies?
Date: Mon, 7 Jul 2008 13:21:20 -0700 (PDT)
Organization: http://groups.google.com
Lines: 22
Message-ID: <089e3f31-361b-4bca-af30-7d5022ffd48b@f36g2000hsa.googlegroups.com>
References: <g3vlk2$6nf$1@aioe.org> <r24864l3hq7evilchjblbdm00hgvmhle0r@4ax.com> 
 <48641b7e$0$4066$9a566e8b@news.aliant.net> <5df510ce-9cbd-4260-b5bc-1ac8ba0b17ba@e39g2000hsf.googlegroups.com> 
 <f219a6bd-9d8e-4cfe-9d60-ce9dcaeff16d@z66g2000hsc.googlegroups.com> 
 <nFD9k.5753$LG4.2422@nlpi065.nbdc.sbc.com> <wq4bk.28$0V1.10@trndny01> 
 <gI6bk.11000$cW3.8591@nlpi064.nbdc.sbc.com> <D8ubk.240$rb1.211@trndny08> 
 <zOvbk.31378$ZE5.24693@nlpi061.nbdc.sbc.com> <jSwbk.249$rb1.205@trndny08> 
 <3Yxbk.21319$co7.18979@nlpi066.nbdc.sbc.com> <6ad51b62-e66a-4daa-b21c-c361fd6b22f8@8g2000hse.googlegroups.com> 
 <4wJbk.112$0V1.4@trndny01>
NNTP-Posting-Host: 90.192.114.44
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
X-Trace: posting.google.com 1215462080 18061 127.0.0.1 (7 Jul 2008 20:21:20 GMT)
X-Complaints-To: groups-abuse@google.com
NNTP-Posting-Date: Mon, 7 Jul 2008 20:21:20 +0000 (UTC)
Complaints-To: groups-abuse@google.com
Injection-Info: f36g2000hsa.googlegroups.com; posting-host=90.192.114.44; 
 posting-account=H0ckjQoAAADRgkguzQRGVwl65wXgA5te
User-Agent: G2/1.0
X-HTTP-UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.15) 
 Gecko/20080623 Firefox/2.0.0.15,gzip(gfe),gzip(gfe)
Xref: usenetserver.com comp.databases.theory:171926
X-Received-Date: Mon, 07 Jul 2008 16:21:20 EDT (text.usenetserver.com)

On Jul 5, 1:09 pm, "David Cressey" <cresse...@verizon.net> wrote:
> "Marshall" <marshall.spi...@gmail.com> wrote in message
>
> news:6ad51b62-e66a-4daa-b21c-c361fd6b22f8@8g2000hse.googlegroups.com...
>
> > What can be meaningfully asked is determined by the schema.
>
> > If the schema specifies that the weight attribute is nullable,
> > then the question of how much a shipment weighs in total
> > is a question that cannot be asked.
>
> > Marshall
>
> Bingo!

However, one /can/ validly ask "please give me the minimum the
shipment weighs" and this may still be very useful. This is of course
not a defence of null markers (obviously not. its me), but rather just
a precaution against ruling out all questions of irregular data in
blanket fashion. Our aim should be to provide frameworks that allows
us to ask these questions with syntactic correctness /and/ as
parsimoniously as possible.