Re: Database normalization

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От Andrew Sullivan
Тема Re: Database normalization
Дата
Msg-id 20070828132604.GB461@phlogiston.dyndns.org
обсуждение исходный текст
Ответ на Re: Database normalization  ("Sebastian Ritter" <ritter.sebastian@gmail.com>)
Ответы Re: Database normalization  ("Sebastian Ritter" <ritter.sebastian@gmail.com>)
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On Tue, Aug 28, 2007 at 12:47:45PM +0100, Sebastian Ritter wrote:
> > The update/message format is exactly the same for both. Should I make two
> > different tables:

> >   one table with extra columns : is_client, client_id, service_id, where
> > either client_id or service_id would be null depending on the is_client
> > boolean?

Is the rest of the data the same?  If so, then one table is right. 
If not, then more than one table.  In either case, I really hate the
idea of two columns, one of which is always null.  But if you're
going to do that, make sure you add a CHECK constraint where !(col1
IS NULL and col2 IS NULL).

A

-- 
Andrew Sullivan  | ajs@crankycanuck.ca
I remember when computers were frustrating because they *did* exactly what 
you told them to.  That actually seems sort of quaint now.    --J.D. Baldwin


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