Re: Unique or Primary Key?

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От Bruce Richardson
Тема Re: Unique or Primary Key?
Дата
Msg-id 20010503.17004700@usb.cafod
обсуждение исходный текст
Ответ на Re: Unique or Primary Key?  (GH <grasshacker@over-yonder.net>)
Ответы RE: Unique or Primary Key?  ("Christian Marschalek" <cm@chello.at>)
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On 5/3/01, 2:29:09 AM, GH <grasshacker@over-yonder.net> wrote regarding
Re: [GENERAL] Unique or Primary Key?:



> Just to expand on Eric's response, a Primary Key directive creates a
> unique not null column, whereas a unique column can be null. In this
> instance, your columns are already not null, so, as Eric responded, it
is
> basically the same thing.

OK.  I was just worried that there might be some more subtle issues
regarding query/index optimisation.

Besides, I couldn't see much use in creating it as a primary key.  How
would I ever reference it from another table?

--

Bruce





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