Oracle FAQ Your Portal to the Oracle Knowledge Grid
HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US
 

Home -> Community -> Usenet -> comp.databases.theory -> Re: Key attributes with list values was Re: What are the differences ...KEY

Re: Key attributes with list values was Re: What are the differences ...KEY

From: Brian Selzer <brian_at_selzer-software.com>
Date: Sun, 26 Feb 2006 03:50:15 GMT
Message-ID: <Xz9Mf.37664$F_3.21295@newssvr29.news.prodigy.net>


> I definitely agree with that philosophy. It was just a
> for-what-it's-worth - if there were some added complexity to permitting
> list values in candidate keys, it is not a feature many would use or
> need.

It's also insane. Using a list--or any non-scalar value for that matter--as a prime attribute introduces ambiguity and redundancy into the data model. For example, if the contents of the list changes, does that signal a key change? What I'm trying to convey is that from one point of view, a list has identity, regardless of its contents. So is the candidate key the list identity, or is it the permutation of a collection of values? Also, I was under the impression that redundancy is the prime target of the discipline of data modeling. A database is a knowledge respository, and it doesn't make sense to "know" something more than once. Redundancy in a data model causes all sorts of problems, the main one being that the database's responsibility to maintain integrity must necessarily be ceded to the application.

"dawn" <dawnwolthuis_at_gmail.com> wrote in message news:1140916287.800990.284570_at_t39g2000cwt.googlegroups.com...
> Marshall Spight wrote:
>> dawn wrote:
>> >
>> > Since I know you favor including lists, are you planning to permit
>> > candidate keys to have list values?
>>
>> Probably.
>>
>> I'm not taking the approach that I as the designer should try to
>> produce a system in which all bad practice is impossible.
>> That can't be achieved anyway and leads to some undesirable
>> side effects.
>
> I definitely agree with that philosophy. It was just a
> for-what-it's-worth - if there were some added complexity to permitting
> list values in candidate keys, it is not a feature many would use or
> need.
>
> Cheers! --dawn
>
Received on Sat Feb 25 2006 - 21:50:15 CST

Original text of this message

HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US