Path: dp-news.maxwell.syr.edu!spool.maxwell.syr.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!elnk-pas-nf1!newsfeed.earthlink.net!pd7cy1no!pd7cy2no!shaw.ca!pd7urf2no.POSTED!53ab2750!not-for-mail X-Trace-PostClient-IP: 24.84.208.66 From: paul c User-Agent: Thunderbird 1.5.0.4 (Windows/20060516) MIME-Version: 1.0 Newsgroups: comp.databases.theory Subject: Re: Proposal: 6NF References: <1159954091.119164.155490@m73g2000cwd.googlegroups.com> <%zOUg.8386$GR.2556@newssvr29.news.prodigy.net> <1159970386.339044.87090@i42g2000cwa.googlegroups.com> <1160433960.180027.59750@i42g2000cwa.googlegroups.com> <1160439308.677121.226700@i3g2000cwc.googlegroups.com> In-Reply-To: <1160439308.677121.226700@i3g2000cwc.googlegroups.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Lines: 50 Message-ID: Date: Tue, 10 Oct 2006 00:32:28 GMT NNTP-Posting-Host: 64.59.144.75 X-Complaints-To: abuse@shaw.ca X-Trace: pd7urf2no 1160440348 64.59.144.75 (Mon, 09 Oct 2006 18:32:28 MDT) NNTP-Posting-Date: Mon, 09 Oct 2006 18:32:28 MDT Organization: Shaw Residential Internet Xref: dp-news.maxwell.syr.edu comp.databases.theory:45653 dawn wrote: > paul c wrote: >> dawn wrote: >>> Hugo Kornelis wrote: >>>> On Fri, 06 Oct 2006 23:29:29 GMT, paul c wrote: >>>> >>>>> Hugo Kornelis wrote: >>>> (snip) >>>>>> Because relational databases supporting NULL *define* it as a marker >>>>>> denoting the absence of a value. Dawn actually makes a good point about >>>>>> context: in C for instance, NULL has a completely different meaning. >>>>>> ... >>>>> Since it has a different meaning in C, there is no point bringing C into >>>>> play here. >>>> Hi Paul, >>>> >>>> The point I was trying to make is that NULL has different meaning in >>>> different context. Using C as example was a bad choice, since it >>>> obfuscated what I was trying to convey, rather than clarifying it. >>>> >>>> The meaning of NULL in the context of SQL is also quite different from >>>> the meaning of NULL in Pick (and possibly other MV databases). That's >>>> what I wanted to write, and what I should have written in the first >>>> place. Much of the discussion between Cimode and Dawn appears (as I read >>>> it) to come from Cimode talking aboout SQL NULL and Dawn talking about >>>> Pick NULL - but they both think that the other is discussing the same >>>> NULL. >>> Thanks for giving your take on that, Hugo, since I was clearly getting >>> nowhere. >> What else is new. >> >> You won`t get anywhere as long as you keep comparing apples to oranges, >> eg., imagining that Pick has a data model that is comparable to what >> Codd had in mind. > > That is not what this was about, Paul. Yes, it is, see below. There are many languages that > employ 2VL. SQL is the odd-ball out. You are still talking languages, not r.d. Theory. Too bad I can`t quote Codd here. But just in an effort to get you on a more useful track, did SQL endorse Nulls before or after Codd`s 1979 paper (question mark intended, sorry the keyboard is fine, something to do with whatever Mozilla is doing to firefox or thunderbird). p