Path: newssvr20.news.prodigy.com!newsmst01.news.prodigy.com!prodigy.com!prodigy.com!rip!chi1.webusenet.com!news.webusenet.com!cyclone1.gnilink.net!small1.nntp.aus1.giganews.com!border1.nntp.aus1.giganews.com!intern1.nntp.aus1.giganews.com!nntp.giganews.com!nntp.golden.net!news.golden.net.POSTED!not-for-mail NNTP-Posting-Date: Tue, 11 Nov 2003 10:42:03 -0600 From: "Bob Badour" Newsgroups: comp.databases.theory References: <3567017.1068124091@dbforums.com> <1b0b566c.0311070332.54a041e@posting.google.com> <64ea97cf.0311090213.38942cc@posting.google.com> <_%7sb.173236$Fm2.151658@attbi_s04> Subject: Re: Is relational theory irrelevant? (was Re: Dreaming About Redesigning SQL) Date: Tue, 11 Nov 2003 11:41:29 -0500 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Message-ID: Lines: 44 NNTP-Posting-Host: 207.35.144.158 X-Trace: sv3-3mQByjltcKS4FrPQLPE5eglkP5xX8MXQ1h14APxTU1iJdbXbLPj9RnVNO5pknkxJirIC3WCxZrJIYzl!bCGHnLse1KZQL/7mWz3GWVFnVWvoRyhABJ2MERwkjJG5a54+NjBcjAaYgQHaq61bt/gr+IF0RA== X-Complaints-To: abuse@golden.net X-DMCA-Complaints-To: abuse@golden.net X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.1 Xref: newssvr20.news.prodigy.com comp.databases.theory:22627 "Marshall Spight" wrote in message news:_%7sb.173236$Fm2.151658@attbi_s04... > "Bob Badour" wrote in message news:sZqdnURpMcikvzKi4p2dnA@golden.net... > > > > Express a quota query. > > > > > > select top 5 * from ( > > > select * from emp order by sal > > > ) > > > > > > What is the problem, besides "5*from" looking ugly? > > > > The ordered operand. > > I'm sorry, but I'm totally at a loss as to why that's a problem. > Any references for further info? Relations have no order. The ordered operand implies some conversion to a different type that is ordered, which then changes the logical model from a "relational model" to a "relational and something else model". > In fact, here's a larger question: it seems to me that neither > SQL nor TTM make adequate provisions for the difference > between well-ordered relations and partially-ordered relations. Relations have no order. What provisions for order would either provide for an unordered structure? > It seems to me the two cases have to be considered separately: > the partially-ordered relation will be subject to the issues > (specifically: ties) discussed in Practical Issues in Database > Management (bing!: could that be what you're talking about, > above?) but the well-ordered relation is not. And I think > we'd want to preserve the distinction. > > For example, we know if we sort using a total ordering function > on a key column that we will have no ties. Sorting is physical when dealing with an unordered logical structure and may not even be required.