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Re: Database design question

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Mon, 26 Jun 2006 19:36:58 GMT
Message-ID: <uHWng.2597$pu3.62899@ursa-nb00s0.nbnet.nb.ca>


sreedhardasi_at_gmail.com wrote:

> Bob Badour wrote:
>

>>sreedhardasi_at_gmail.com wrote:
>>
>>
>>>I have a database design questions. How can we specify one of two
>>>columns in a table should be not null? In other words, if one column is
>>>
>>>null then another column should not be null.
>>
>>The simple answer is to avoid null in the first place. Null will affect
>>the validity of everything it touches.

>
> Thanks for your reply. How can we avoid nulls? If document has group
> level permissions, then what will be the value for the user id (Just
> blank)?

I might suggest the Principle of Orthogonal Design (POOD) would give some clues. I think you might get a few more from Fabian Pascal's _Practical Issues in Database Management_ -- especially the sections on sub-types. Received on Mon Jun 26 2006 - 14:36:58 CDT

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