Re: General question about fk constraints ...

"Jan Gelbrich" <j_gelbrich_at_westfalen-blatt.de> wrote in message news:<b27ql8$1a92b9$1_at_ID-152732.news.dfncis.de>...
> ... that is: about the drive of many software vendors to *avoid* them ...
>
> Hello !
>
> Just as a matter of interest, I would like to know *why* are so many data
> models implemented out there
> are neglecting fk constraints to a degree that it makes me almost mad -
> sorry ...
>
> When I was trained in ER design 1 and 1/2 year ago,
> we were told never to sacrifice fk constraints for the douptful sake
> of performance,
> and we set up easy-to-read ERMs with countable table numbers and so on ...
>
> Now, on my working place I see (and from many others I hear) that it seems
> very common
> *not* to use constraints, just for the sake of performance - all the guys
> around me say that, and they are
> just asking "R U kidding ?! *Why* for *** sake do You wanna use constraints
> ?! *You* as dba shoulda known better ... "
> which makes me almost speechless for a moment 8|
>
> On a recent post in the Oracle NGs I read that Peoplesoft and SAP are going
> just the same way, having
> thousands of tables in their apps. No way to Reverse Engineer because just
> by viewing the ERM, nothing can be
> understood.
>
> Am I too cynic when I come to think that all this is just to hide their apps
> logics behind a labyrith of tables,
> or does this general avoidance of constraints have a meaning that I still do
> not happen to understand ?
>
>
> Maybe this is a straight newbee question, but I really would appreciate any
> comments.
>
> TIA
>
> Jan

Jan, I think vendors leave FK constaints out of their products for two reasons. One, they intend to port their product to multiple databases and either they do not know if the database supports FK constains in the same manner or they just do not want to deal with the differences. And two, the vendor wants to make reverse engineering more difficult.

In point of fact enforcing FK constaints in the database instead of in the application is generally faster. Some adhoc query tools use FK information to guide their generated join code. There are other advantages to using FK declared within the database.

HTH -- Mark D Powell -- Received on Mon Feb 10 2003 - 12:00:14 CST