From: Jim C. Nasby <jnasby@pervasive.com>
To: L van der Walt <mailing@lani.co.za>
Cc: pgsql-sql@postgresql.org
Cc: pgsql-general@postgresql.org
Subject: Re: A Not Join
Date: Tue, 1 Nov 2005 09:15:04 -0600
Message-ID: <20051101151504.GL20349@pervasive.com> (raw)
In-Reply-To: <43677B35.6010005@lani.co.za>
References: <43677B35.6010005@lani.co.za>
On Tue, Nov 01, 2005 at 04:27:01PM +0200, L van der Walt wrote:
> I have three table:
> Users - Contains username, ID etc...
> Permissions - A permission name and ID
> Link up table - The user.id and permission.id
>
> If a user.id and a permission.id row exists in the linkuptable the user
> have that permission granted.
>
> With the statement below I can see the permissions a user have.
>
> SELECT users.username, permissions.name
> FROM users INNER JOIN linkuptable
> ON (users.id = linkuptable.userid)
> INNER JOIN permissions
> ON (permissions.id = linkuptable.permissionid)
> WHERE users.username = 'DummyUser'
>
> How do I see the permissions that user DON'T have with a fast SQL statement.
>
> Thus, a NOT the statement for the above SQL statement
LEFT JOIN permissions ON (...)
WHERE permissions.id IS NULL
You might have to do the NULL check in a HAVING clause instead... try
it.
BTW, this is probably better asked on pgsql-sql.
--
Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
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To: pgsql-sql@postgresql.org
Cc: jnasby@pervasive.com, mailing@lani.co.za, pgsql-general@postgresql.org
Subject: Re: A Not Join
In-Reply-To: <20051101151504.GL20349@pervasive.com>
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