[thelist] Constraint/trigger help
Jeffrey Barke
jeffrey.barke at themechanism.com
Fri May 18 09:57:09 CDT 2007
Bill,
Instead of storing the default mailbox in the user table, you could
add a boolean field in the mailbox table to indicate default status.
This would solve your integrity and circular reference concerns.
Jeffrey
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Cheers.
Jeffrey Barke
jeffery.barke at theMechanism.com
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On May 18, 2007, at 2:17 AM, Bill Moseley wrote:
> Say I have a mail reader application where people can create their own
> mailboxes (folders). So I have a table:
>
> create table mailbox (
> id integer,
> name text,
> owner int references user(id)
> );
>
> So, now the user table should store their default mailbox
> (ignoring that I've referenced user above before defining it)
>
> create table user (
> id integer,
> name text,
> email text,
> default_mailbox integer references mailbox(id)
> );
>
> How can I ensure (in the database) that default_mailbox references a
> mailbox that has its owner set to the same user? Obviously, don't
> want one user's default mailbox to reference another user's mailbox.
>
> I'm not thrilled by the circular references there.
>
>
> --
> Bill Moseley
> moseley at hank.org
>
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