David Cressey schrieb:
> "Mike Meng" <meng.yan_at_gmail.com> wrote in message
> news:1124349957.125386.120320_at_g49g2000cwa.googlegroups.com...
>
>>Hi all,
>> I'm enjoying reading C. J. Date's new book "Database in Depth", in
>>which I know the www.dbdebunk.com website. I visited the site just now,
>>and find the following statement in its "QUOTE OF THE WEEK" section:
>>
>>** QUOTE **
>>Don't use primary keys that have meaning for the end user, such as
>>invoice number or the ISBN value.
>>
>>--Giuseppe DiMauro & Francesco Balena, PRACTICAL GUIDELINES AND BEST
>>PRACTICES FOR MICROSOFT VISUAL BASIC AND VISUAL C# DEVELOPERS
>>** QUOTE **
>>
>> It seems that they quote this idea to point out how wrong it is. But
>>I myself always regard this idea as a good practice in database design!
>>Am I right? If not, what's wrong with it? Please comment.
>>
>
>
>
> It depends. There are times when it's wise to use keys like ISBN and
> invoice number, and times when it's not.
>
> The important factor is not whether the user understands the keys or does
> not, but whether new instances of real world entities come with dependable
> keys or not.
>
> Examples: depending on Social Security # to identify persons is a bad idea,
> if you are going to be faced with a significant number of people that don't
> have an account with Social Security. example: the prison inmate
> population.
>
> Depending on ISBN to key books in a library is a bad idea if you are going
> to have a significant number of books that come without an ISBN, like
> certain government publications.
>
> And, of course, the generator has to avoid duplicates, among other issues.
>
> There are other cases where surrogate keys are a good idea.
>
> But, in general, Date is right. Natural keys are better, as long as they
> are dependable.
>
> It's not a dogmatic question. There are situation where one choice is
> right, and others where the other choice is right.
>
> And that's what I don't like about dogmatic responses. They tend to assume
> that design judgements fall on a simple linear scale from badness to
> goodness. Goodness is not a one dimensional measure. And that's why I stay
> way from dbdebunk.
> At a deeper level, they don't get it.
The main problem of dbdebunk is that they do not propose anything new
and their main argument is that we do not need anything new because we
have already one good theory and that is enough -- the main problem (in
their opinion) is that this theory is not used correctly and there exist
bad boys who do not understand it (bad programmers, bad database
developers and so on). Those bad boys produce bad products and try to
enhance this ultimate theory and its is crime. Why that theory is good?
Just because it is based on set theory (stupid argument, is not it). I
would qualify dbdebunk as religious fanatics who identify themselves
with this one theory and speak on bahalf of it. They think their role
consists in protecting this theory and the way they chose consists in
isolating it from the outside world, frozing in its current state and
fighting with any type of heretics. So it is really dogmatic and
orthodox site (unfortunately). And anybody who wants to learn something
new, unusual, surprising and interesting should keep a distance from
this site because they think that they know what truth is.
--
http://conceptoriented.com
Received on Fri Aug 19 2005 - 12:03:06 CDT
