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Re: Oracle NULL vs '' revisited

From: DA Morgan <damorgan_at_psoug.org>
Date: Sat, 25 Aug 2007 10:30:23 -0700
Message-ID: <1188063020.42468@bubbleator.drizzle.com>


Frank van Bortel wrote:
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> Tony Rogerson wrote:

>>> The point was to demonstrate the surrogate keys are worthless
>>> for purposes of data integrity with most data. What ends up
>>> happening is that unique constraints are then built, on top of
>>> the surrogate key, in an attempt to do what the surrogate can
>>> not.
>> Oh really?
>>
>> Then why say this "Natural keys can not change. If it can change IT IS
>> NOT A KEY it is
>> just a value.".

>
> You seem to have it backwards - the mantra is "if keys can change,
> it is likely an attribute, not a key".
>
> You prove Daniels point, by demonstrating natural keys change
> (and *thus* *should* not have been used as keys)
>> You seem to be under the impression that "Natural keys can not change".
>>

>
> The should not, when used in programs. This is different from the
> fact they change.
> Loosely quoted, you stated "ISO country codes are not keys, as
> they change".
>
> Well - if you knew that from the start (and you should) - if
> used in a system, that is not expected to cope with those changes,
> it is acceptable.
> For Customs, I'd advise not to use it as a key, but just as a value.
>
> It seems you gentlemen are in agreement, you are just looking at
> the question at hand from two different angles.
> - --
> Regards,
> Frank van Bortel
>
> Top-posting is one way to shut me up...
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ISO Country Codes are a perfectly valid natural key in a lookup table where each code uniquely identifies a country. When then put into another table, and validated via a referential constraint, they are not a natural key: Natural or unnatural.
-- 
Daniel A. Morgan
University of Washington
damorgan_at_x.washington.edu (replace x with u to respond)
Puget Sound Oracle Users Group
www.psoug.org
Received on Sat Aug 25 2007 - 12:30:23 CDT

Original text of this message

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