Re: RM VERY STRONG SUGGESTION 4: TRANSITION CONSTRAINTS
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Sat, 04 Sep 2010 00:42:42 -0300
Message-ID: <4c81c03d$0$11831$9a566e8b_at_news.aliant.net>
>
> <snip>
>
>
> In the update, the referent of t1 is the referent of t2, but in the
> multiple assignment, the referent of t1 ceased to exist and the
> referent of t2 came into existence. The "meaning" of the fact "t2" is
> therefore different. For example,
Date: Sat, 04 Sep 2010 00:42:42 -0300
Message-ID: <4c81c03d$0$11831$9a566e8b_at_news.aliant.net>
Brian wrote:
> On Sep 3, 2:29 pm, Erwin <e.sm..._at_myonline.be> wrote:
>
>>On 3 sep, 17:35, Brian <br..._at_selzer-software.com> wrote:
>
> <snip>
>
>>>UPDATE is not the same as a combination of DELETE-then-INSERT, but not
>>>because of some objectid.
>>
>>It is the same. Always. Before some update, relvar R has value
>>{t1}. After that update, relvar R has the value {t2}.
>>
>>Please explain what the difference is between this update and a
>>multiple assignment consisting of the delete of t1 and the insert of
>>t2.
>
> In the update, the referent of t1 is the referent of t2, but in the
> multiple assignment, the referent of t1 ceased to exist and the
> referent of t2 came into existence. The "meaning" of the fact "t2" is
> therefore different. For example,
I disagree. At the logical level of discourse, both assignments are the same. Received on Sat Sep 04 2010 - 05:42:42 CEST