From: | Jorge Godoy <jgodoy(at)gmail(dot)com> |
---|---|
To: | pgsql-sql(at)postgresql(dot)org |
Subject: | Re: Composite UNIQUE across two tables? |
Date: | 2008-03-07 02:22:27 |
Message-ID: | 200803062322.27911.jgodoy@gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-sql |
Em Thursday 06 March 2008 22:10:14 Jamie Tufnell escreveu:
>
> I already have site_id in the users table and I can determine the
> site_group_id from that. So it seems redundant to me, to store
> site_group_id for each user as well. Also, I'm not sure how I would
> enforce that the site_group_id added to the users table would
> correspond correctly with the site_id (as per the sites table).
> Perhaps I would make a composite foreign key?
Or you manage site_group_id from a trigger. When the user creates / chooses a
site_id and updates/inserts this information then you fill site_group_id with
a trigger. This way you guarantee the correctness of this parameter.
> I've never come up against this situation before, and because of the
> reasons above, I'm getting the feeling there might be a better way to
> design this.
Again, a trigger can do that. Slower than denormalizing the database, but it
can be done.
--
Jorge Godoy <jgodoy(at)gmail(dot)com>
From | Date | Subject | |
---|---|---|---|
Next Message | Bart Degryse | 2008-03-07 07:46:24 | Re: Composite UNIQUE across two tables? |
Previous Message | Jamie Tufnell | 2008-03-07 01:10:14 | Re: Composite UNIQUE across two tables? |