Re: Seeking Database Design Guide

RE:     Re: Seeking Database Design Guide
< Big Snip >
>More recently I have thrown all that away and begun writing systems
>where the unique key is defined on the physical file and the physical is
>defined directly in programs. I'm happy to report that the sky has not
>fallen in. Again without starting a war, I would appreciate it if
>someone who is thoroughly familiar with the theoretical arguments on
>both sides could summarise them for us.
>Dave Kahn - TCO, Tengiz, Kazakstan

Dave
If the unique key is on the Physical you never run the risk of Dups.
If unique is on the Logical there could be multiple reasons/times when
the unique key is not present(LF deleted, Not Restored, etc. etc.)

Also it makes the identification or finding process easier. "Just Look At
The Physical"

I understand and agree with your statement "the idea that programs should not
be concerned with the physical representation of the data base"
But it always was common sense to me that "If every file needed one, 
and The Physical is the first built"  it should be on it.  

After all we have many Physicals without any logicals.  It would seem like 
complications for complications sake to artifically have to have a logical
just for a unique key when you have the physical already.

IMHO
John Carr
EdgeTech 
 
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* This is the Midrange System Mailing List!  To submit a new message,   *
* send your mail to "MIDRANGE-L@midrange.com".  To unsubscribe from     *
* this list send email to MAJORDOMO@midrange.com and specify            *
* 'unsubscribe MIDRANGE-L' in the body of your message.  Questions      *
* should be directed to the list owner / operator: david@midrange.com   *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *