Path: news.f.de.plusline.net!news-fra1.dfn.de!newsfeed.ision.net!newsfeed2.easynews.net!ision!newsfeed.freenet.de!newspeer1.nwr.nac.net!border2.nntp.dca.giganews.com!nntp.giganews.com!pd7cy1no!pd7cy2no!shaw.ca!pd7urf1no.POSTED!53ab2750!not-for-mail X-Trace-PostClient-IP: 24.84.208.66 From: paul c User-Agent: Mozilla Thunderbird 1.0.7 (Windows/20050923) X-Accept-Language: en-us, en MIME-Version: 1.0 Newsgroups: comp.databases.theory Subject: Re: Why relational division is so uncommon? References: <1177525004.714698.115410@t39g2000prd.googlegroups.com> <1177607284.813162.87940@t38g2000prd.googlegroups.com> In-Reply-To: <1177607284.813162.87940@t38g2000prd.googlegroups.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Lines: 18 Message-ID: Date: Thu, 26 Apr 2007 23:16:47 GMT NNTP-Posting-Host: 64.59.144.74 X-Complaints-To: abuse@shaw.ca X-Trace: pd7urf1no 1177629407 64.59.144.74 (Thu, 26 Apr 2007 17:16:47 MDT) NNTP-Posting-Date: Thu, 26 Apr 2007 17:16:47 MDT Organization: Shaw Residential Internet Xref: news.f.de.plusline.net comp.databases.theory:43524 Vadim Tropashko wrote: ... >>I notice also that the example doesn't suggest a lot of activity, other >>than bureaucratic activity, this company might go out of business soon >>if there is no "sales" or "orders" or "inventory" relations. Lots of >>other useful queries would then arise, "who has paid all their invoices >>on time?", "which students have passed all course exams?". > > > Quite an interesting perspective. Although, the query "who has paid > all their invoices > on time?" doesn't seem to be a relational division (what relation are > you dividing into?) > ... Customers? p