From: Achilleus Mantzios <achill@matrix.gatewaynet.com>
To: Robert Treat <xzilla@users.sourceforge.net>
Cc: pgsql-sql@postgresql.org
Subject: Re: partial unique constraint
Date: Tue, 6 Apr 2004 18:18:03 +0300 (EEST)
Message-ID: <Pine.LNX.4.44.0404061752300.4620-100000@matrix.gatewaynet.com> (raw)
In-Reply-To: <1081261772.31785.48.camel@camel>
O kyrios Robert Treat egrapse stis Apr 6, 2004 :
> Trying to come up with the proper syntax to meet the following criteria:
>
> create table foo (bar integer, baz boolean UNIQUE (bar, baz = true));
You could simply leave your table as is.
A null vale on baz (equivalent of 'false') will have no impact on the
constraint.
A 't' value (equivalent to 'true') will enforce the constraint.
In other words you can convert your problem as
baz == null <==> baz='false'
baz == 't' <==> baz='true'
(you must never use baz='f')
>
> note the above syntax is not correct, but should demonstrate what i'm
> trying to do; I want to add a unique constraint such that we only allow
> one case of bar and baz = true... i can have unlimited bar and baz =
> false, and there can be multiple bar and baz = true if the bars are
> different... did some doc reading and mail list searching but a valid
> syntax for this seems to be escaping me...
>
> btw I'm pretty sure I could do this with an external trigger, but am
> wondering about a constraint oriented approach
>
> Robert Treat
>
--
-Achilleus
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To: pgsql-sql@postgresql.org
Cc: achill@matrix.gatewaynet.com, xzilla@users.sourceforge.net
Subject: Re: partial unique constraint
In-Reply-To: <Pine.LNX.4.44.0404061752300.4620-100000@matrix.gatewaynet.com>
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