Re: A Not Join - Mailing list pgsql-general

From Jerry Sievers
Subject Re: A Not Join
Date
Msg-id m34q6v7ph5.fsf@prod01.jerrysievers.com
Whole thread Raw
In response to A Not Join  (L van der Walt <mailing@lani.co.za>)
List pgsql-general
L van der Walt <mailing@lani.co.za> writes:

> 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.
>

Simple.

select permname
from permissions
where permid not in (
    select permid
from linkage
    where userid = 'dummy'
);

Or... a slick way to get the anti-permission for the whole bunch of
users is to;

cross join the userids with permids and then EXCEPT SELECT from
linkage table to filter out the active permissions.

Have fun!


--
-------------------------------------------------------------------------------
Jerry Sievers   305 854-3001 (home)     WWW ECommerce Consultant
                305 321-1144 (mobile    http://www.JerrySievers.com/

pgsql-general by date:

Previous
From: Douglas McNaught
Date:
Subject: Re: Cannot install -- "/lib/cpp" failed sanity check
Next
From: Tony Caduto
Date:
Subject: Part of original Postgresql cook book back online