From: codeWarrior <gpatnude@hotmail.com>
To: pgsql-sql@postgresql.org
Subject: Re: select based on multi-column primary keys
Date: Tue, 23 Jan 2007 13:07:19 -0800
Message-ID: <ep5t77$oqt$1@news.hub.org> (raw)
References: <45B16602.2080508@furthernorth.net>
<eos326$13fv$1@news.hub.org>
<20070121152838.GB3533@phlogiston.dyndns.org>
No... its a table constraint using a unique, implicit index on the listed
columns. .
PRIMARY KEY ( column [, ...] )
The PRIMARY KEY table constraint is similar to the PRIMARY KEY column
constraint. As a table constraint, PRIMARY KEY allows multiple columns to be
defined in a parenthetical expression, separated by commas. An implicit
index will be created across columns. The combination of values for each
column specified must therefore amount to only unique and non-NULL values,
as with the PRIMARY KEY column constraint.
hehehe....
"Andrew Sullivan" <ajs@crankycanuck.ca> wrote in message
news:20070121152838.GB3533@phlogiston.dyndns.org...
> On Fri, Jan 19, 2007 at 07:45:40PM -0800, codeWarrior wrote:
>> AFAIK: You cannot have multiple primary keys. How would you know which
>> one
>> is the actual key ?
>
> You can have a multi-column primary key, though. That's a perfectly
> legitimate approach.
>
>> FYI: What you are really talking about are table contraints... When you
>> have
>
> No, it's a multi-column primary key.
>
>> My advice would be to alter your table structure so that you have a
>> "real"
>> PK not table constraints -- that would make it searchable....
>
> This is already searchable. What you are talking about is not a real
> primary key, but an artificial one. The OP already has a real
> primary key. SQL purists think artificial primary keys mean that you
> haven't done enough normalisation. I'm going to remain silent on
> that topic, though, so that we don't get a Thread That Does Not End
> :)
>
> A
>
>
> --
> Andrew Sullivan | ajs@crankycanuck.ca
> If they don't do anything, we don't need their acronym.
> --Josh Hamilton, on the US FEMA
>
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To: pgsql-sql@postgresql.org
Cc: gpatnude@hotmail.com
Subject: Re: select based on multi-column primary keys
In-Reply-To: <ep5t77$oqt$1@news.hub.org>
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