Re: a union is always a join!

"Brian Selzer" <brian_at_selzer-software.com> wrote in message news:TJ%yl.24805$yr3.3171_at_nlpi068.nbdc.sbc.com...
>
> "Walter Mitty" <wamitty_at_verizon.net> wrote in message
> news:HrHxl.1597$6%.913_at_nwrddc01.gnilink.net...
>
> <snip>
>
>> Tegiri opined as to how an update is essentially the same thing as a
>> delete
>> followed by an insert. An eminently reasonable proposition,
>> given that any delta in a database that can be caused by an update can
>> also
>> be caused by a suitable delete followed by a suitable insert.
>
> If a user issues an insert, isn't it reasonable to assume that it concerns
> something that isn't already represented in the database? If a user
> issues a delete, isn't it reasonable to assume that it concerns something
> that shouldn't still be represented in the database? If a user issues an
> update, isn't it reasonable to assume that it concerns something that
> should still be represented in the database? If those assumptions are
> reasonable, then the assumption that an update is essentially the same
> thing as a delete followed by an insert isn't.
>
> The assumption that an update is essentially the same thing as a delete
> followed by an insert effectively denies that there is a connection
> between a database and the universe of discourse. And that is just
> absurd.
>
> <snip>
>

It's exactly the opposite, Brian. The assertion that a given state of the database makes different assertions about the UofD depending on how the database got to that state is what breaks the connection between the database and the UofD. It's the current state of the database, and not the history of the database, that makes assertions about the UofD.

This is the nub of the debate between you and me. Let's let it rest here. I'm not going to change your mind. And you're not going to change my mind, or the minds of most of the participants. Received on Fri Mar 27 2009 - 13:15:15 CET