Re: Separate PK in Jxn Tbl?

From: Brian Selzer <brian_at_selzer-software.com>
Date: Fri, 01 Feb 2008 15:16:37 GMT
Message-ID: <pJGoj.5310$Ch6.4244_at_newssvr11.news.prodigy.net>


"David Cressey" <cressey73_at_verizon.net> wrote in message news:wOFoj.5442$4f.4907_at_trndny06...
>
> "Brian Selzer" <brian_at_selzer-software.com> wrote in message
> news:oMAoj.5076$5K1.904_at_newssvr12.news.prodigy.net...
>>
>> "Roy Hann" <specially_at_processed.almost.meat> wrote in message
>> news:1IKdncuZltPXVj_anZ2dneKdnZydnZ2d_at_pipex.net...
>> > "Brian Selzer" <brian_at_selzer-software.com> wrote in message
>> > news:p9uoj.5279$0o7.473_at_newssvr13.news.prodigy.net...
>> >>
>> >> Constraints should always be checked by the DBMS, not by applications.
>> >
>> > I agree very heartily with the first part of this statement, for the
>> > reasons you give below. I disagree with the second part (as stated).
>> > There is no reason why applications shouldn't also test what
>> > constraints
>> > they can. The problem is that they should not have hand-coded
>> > re-implementations of the constraints because those will get out of
>> > sync
>> > with the database over time. What would be very nice is if one day it
> were
>> > possible for applications to download the relevant constraints at
>> > run-time, the way they presently download other metda-data.
>> >
>>
>> That's a good point. I should have said instead, "Constraints should
> always
>> be /enforced/ by the DBMS, not by applications." It is often a good
>> thing
>> for an application to do some checking because it can reduce the number
>> of
>> round-trips, and maybe even some transaction rollbacks.
>
> I think that if an application does some checking, it will also do some
> enforcing.
>
> I think you might have been aiming at something like the following:
>
> The DBMS should always enforce the constraints that it can enforce, rather
> than relying on applications to refrain from writing data that violates
> the
> constraints.
>
> Note that the above is silent on what applications should or should not do
> regarding constraints.
>

Yes.
>
Received on Fri Feb 01 2008 - 16:16:37 CET

Original text of this message