Re: design question

From: Heinz Huber <XhhuberX_at_no-racon-linz.at-no>
Date: Wed, 22 Jan 2003 08:41:51 +0100
Message-ID: <3e2e4b3f$0$20418$91cee783@newsreader02.highway.telekom.at>

stu wrote:
> "Tobin Harris" <comedyharris_at_hotmail.com> wrote in message
> news:b0h3qk$nmsc4$1_at_ID-135366.news.dfncis.de...
> Personally, I haven't got used to working with super/subtype
>

>>tables, and in practice I would create a union view for this instead

>
> (anyone
>

>>feel free to correct me if you feel this is a bad idea).

>
>
> I think what you do in this case is have a users table with a primary key
> (ID).
>
> Then since teachers and students both are of type User the Primary key for
> teachers will be the foreign key Users.ID combined with a new ID for
> teachers. A similar thing should happen for the students table.
>
> At least this is what I think is a correct way to model super-sub type
> relations. Again if somebody knows better please tell me im talking crap!

As soon as you have a supertype, you don't have to create new surrogate keys for the subtypes. If teacher/student ID are generated values, you can simply use Users.ID since that value is unique anyway.

Heinz Received on Wed Jan 22 2003 - 01:41:51 CST