No problem.  Glad to be of help.

If you have a CraneType column in the master table then you could use that to determine which other table has associated data for that Crane.  i.e. if CraneType = "ROUGHTERRAIN" then look in the RoughTerrainCrane table.

Brad


> Date: Tue, 29 Jan 2008 10:04:26 -0800
> From: mz_tricsta@yahoo.com
> To: derby-user@db.apache.org
> Subject: RE: Determine which child table a record belongs to
>
>
> Thanks for your help, Brad. You are absolutely right. In this case, it
> doesn't make sense to have so many tables. I will make the changes you
> suggest. However, there are times when it does make sense to have this kind
> of hierarchical structure such as when the child tables have different
> fields, so my question remains: How would I determine which of the child
> tables the key belongs to without querying each child table? I appreciate
> any further assistance.
>
> Again Thanks,
> Tricsta
>
>
> Brad Moore wrote:
> >
> > Can I suggest changing the "Crane" table to include a CraneType column or
> > something similar? I don't know if there is a reason that's not obvious
> > to me why you need all of the other tables. It looks like you're using
> > the other tables to determine the type of crane, the same thing could be
> > done with one additional column in the Crane table. That would simplify
> > your database design a lot. Unless I'm missing something.
> >
> > Brad
> >
> >
>
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