Path: text.usenetserver.com!out04b.usenetserver.com!news.usenetserver.com!in04.usenetserver.com!news.usenetserver.com!nx01.iad01.newshosting.com!newshosting.com!post01.iad01!news.aliant.net!not-for-mail Date: Wed, 08 Aug 2007 17:20:12 -0300 From: Bob Badour User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040804 Netscape/7.2 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 Newsgroups: comp.databases.theory Subject: Re: NULLs: theoretical problems? References: <46b9b627$0$4048$9a566e8b@news.aliant.net> <1186582837.431878.213670@22g2000hsm.googlegroups.com> <46b9dc62$0$4020$9a566e8b@news.aliant.net> <1186598966.500240.251730@19g2000hsx.googlegroups.com> <46ba14f1$0$4063$9a566e8b@news.aliant.net> <1186603776.661467.76070@19g2000hsx.googlegroups.com> In-Reply-To: <1186603776.661467.76070@19g2000hsx.googlegroups.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Lines: 52 Message-ID: <46ba2544$0$4028$9a566e8b@news.aliant.net> NNTP-Posting-Host: 142.176.76.107 X-Complaints-To: abuse@aliant.net Xref: usenetserver.com comp.databases.theory:166150 X-Received-Date: Wed, 08 Aug 2007 16:19:16 EDT (text.usenetserver.com) Jan Hidders wrote: > On 8 aug, 21:10, Bob Badour wrote: > >>Jan Hidders wrote: >> >>>On 8 aug, 17:09, Bob Badour wrote: >> >>>>Jan Hidders wrote: >> >>>>>On 8 aug, 14:26, Bob Badour wrote: >> >>>>>>sinister wrote: >> >>>>>>>Many discussions point out one deficiency of NULLs: that they collapse >>>>>>>multiple, distinct concepts into one ("no value possible," "value missing," >>>>>>>"value not available at this time", etc). >> >>>>>>>What are the other theoretical problems? My impression from skimming some >>>>>>>threads in this ng is that some anomalies might occur, maybe having to do >>>>>>>with NULLs and joins, or NULLs and keys composed of more than one field, but >>>>>>>I'm not sure. >> >>>>>>The ultimate theoretical problem is a complete lack of any theory >>>>>>underpinning NULL. >> >>>>>Just to avoid any misunderstandings: there has of course been lots of >>>>>theory on certain interpretations of null values, such as the work by >>>>>Raymond Reiter and by Joachim Biskup, but not on the specific meaning >>>>>(if you can call it that) that they were given in SQL. Whether that is >>>>>necessarily a big problem is IMO not so easy to say. >> >>>>In other words, some folks accept that NULL exists without any >>>>theoretical underpinning and then create theories of interpretation. >> >>>Indeed. Because, as we all know, proposing and investigating >>>alternatives is the same as accepting something's existence. >> >>>>How >>>>exactly does that differ from scriptural interpretation and theories >>>>thereof? >> >>>Exactly! Rejecting straight away null values in any form or shape >>>without any sort of investigation of their properties would have been >>>much more scientific. :-) >> >>That doesn't answer the question. How does it differ from scriptural >>interpretation and theories thereof? > > What makes you think they have anything in common? Each relates to interpretation and to an abstract entity taken as a given.