Path: news.cambrium.nl!textnews.cambrium.nl!feeder2.cambriumusenet.nl!feed.tweaknews.nl!209.197.12.246.MISMATCH!nx02.iad01.newshosting.com!newshosting.com!69.16.185.16.MISMATCH!npeer02.iad.highwinds-media.com!news.highwinds-media.com!feed-me.highwinds-media.com!postnews.google.com!n3g2000yqb.googlegroups.com!not-for-mail From: Tony Andrews Newsgroups: comp.databases.theory Subject: Re: boolean datatype ... wtf? Date: Thu, 30 Sep 2010 03:32:58 -0700 (PDT) Organization: http://groups.google.com Lines: 30 Message-ID: References: <8b7a5a2a-1f5b-4778-8238-ca8bd7a00720@a36g2000yqc.googlegroups.com> <3cb332c4-ae45-418d-a1e1-250f42ca52e6@k10g2000yqa.googlegroups.com> NNTP-Posting-Host: 86.4.16.42 Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Trace: posting.google.com 1285842779 1750 127.0.0.1 (30 Sep 2010 10:32:59 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Thu, 30 Sep 2010 10:32:59 +0000 (UTC) Complaints-To: groups-abuse@google.com Injection-Info: n3g2000yqb.googlegroups.com; posting-host=86.4.16.42; posting-account=gSj7NQkAAABlAuBZQxQ3wuVlG7yuQVHa User-Agent: G2/1.0 X-HTTP-UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.2.10) Gecko/20100914 Firefox/3.6.10 ( .NET CLR 3.5.30729; .NET4.0E),gzip(gfe) Xref: news.cambrium.nl On Sep 30, 7:03=A0am, David BL wrote: > On another note, I can easily imagine applications with boolean > attributes that cannot be regarded as derived or calculated from other > information recorded in the database. =A0E.g. soft cover versus hard > cover, read versus unread, fiction versus non-fiction for a book. I am with you there, even though it could be argued that you could have cover_type=3D'soft', status=3D'read', classification=3D'fiction' etc. instead. A pretty common "real world" example in my experience would be where we have to design a database to record data gleaned from the public via a paper or web-based form with lots of "checkbox" questions - e.g. for a car insurance application: [ ] Is the car kept in a locked garage overnight? [ ] Does the car have an immobiliser fitted [ ] Have you made a claim in the past 3 years ... and so on for dozens of questions to which the business needs to know just the Boolean answer. We could again introduce a lot of specific domains like garaged_status ('GARAGED','NOT GARAGED'), but I'm not sure what would be gained by that. Or we could create a plethora of tables like: create table applications_with_garages (application_id references applications primary key); create table applications_with_immobolisers (application_id references applications primary key); ... etc. That may be the right approach in a theoretical true RDBMS, but I'm pretty sure it would get me sacked as a lunatic in any SQL-based DBMS team!