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Message-ID: <446CA301.20305@logix-tt.com>
Date: Thu, 18 May 2006 18:38:25 +0200
From: Markus Schaber <schabi@logix-tt.com>
Organization: Logical Tracking and Tracing International AG, Switzerland
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To: Andreas Joseph Krogh <andreak@officenet.no>
Cc: pgsql-sql@postgresql.org
Subject: Re: Constraint question
References: <200605181541.54299.andreak@officenet.no>
In-Reply-To: <200605181541.54299.andreak@officenet.no>
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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;

HTH,
Markus

-- 
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf.     | Software Development GIS

Fight against software patents in EU! www.ffii.org www.nosoftwarepatents.org