On Thursday 18 May 2006 18:38, Markus Schaber wrote: > Hi, Andreas, > > Andreas Joseph Krogh wrote: > > create table onp_crm_businessfield_company( > > businessfield_id integer not null references onp_crm_businessfield(id), > > company_id integer not null references onp_crm_relation(id), > > is_preferred boolean, > > UNIQUE(businessfield_id, company_id) > > ); > > > > I want a constraint on "is_preffered" so that it's only allowed to be set > > once pr. businessfield_id pr. company so that only one businessfield can > > be preferred for a company. Does anyone have an idea how to enforce this? > > CREATE UNIQUE INDEX foo ON onp_crm_businessfield_company(company_id) > WHERE is_prefferred;
Thanks. I also figured out that an index like this also works: UNIQUE(company_id, is_preferred) This works because NULL = NULL is false. But I guess your solution is cleaner. -- Andreas Joseph Krogh <[EMAIL PROTECTED]> Senior Software Developer / Manager gpg public_key: http://dev.officenet.no/~andreak/public_key.asc ------------------------+---------------------------------------------+ OfficeNet AS | The most difficult thing in the world is to | Hoffsveien 17 | know how to do a thing and to watch | PO. Box 425 Skøyen | somebody else doing it wrong, without | 0213 Oslo | comment. | NORWAY | | Phone : +47 22 13 01 00 | | Direct: +47 22 13 10 03 | | Mobile: +47 909 56 963 | | ------------------------+---------------------------------------------+ ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
