From: Andreas Joseph Krogh <andreak@officenet.no>
To: pgsql-sql@postgresql.org
Subject: Re: Constraint question
Date: Thu, 18 May 2006 21:05:55 +0200
Message-ID: <200605182105.55753.andreak@officenet.no> (raw)
In-Reply-To: <446CA301.20305@logix-tt.com>
References: <200605181541.54299.andreak@officenet.no>
<446CA301.20305@logix-tt.com>
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 <andreak@officenet.no>
Senior Software Developer / Manager
gpg public_key: http://dev.officenet.no/~andreak/public_key.asc
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To: pgsql-sql@postgresql.org
Cc: andreak@officenet.no
Subject: Re: Constraint question
In-Reply-To: <200605182105.55753.andreak@officenet.no>
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