Re: more on delete from join
Date: Fri, 28 Aug 2009 20:29:38 -0300
Message-ID: <4a986869$0$23762$9a566e8b_at_news.aliant.net>
Kevin Kirkpatrick wrote:
> On Aug 28, 4:32 pm, paul c <toledobythe..._at_oohay.ac> wrote:
>
>>Kevin Kirkpatrick wrote:
>>
>>...
>>
>>>>By the way, why assume that CURRENT_USER
>>>>is not updateable?
>>
>>>Great question, cuts to the heart of the matter: It can't be updated
>>>because it is a view. It returns an conclusion, and it is not (IMO)
>>>valid to assert conclusions. ...
>>
>>So A UNION B is a conclusion when assigned to a view, but not a
>>conclusion when assigned to a base. Where does this idea come from and
>>what is it good for, apart from appearing to be a spurious reason to say
>>that views aren't updateable? Even if I were to accept that views
>>aren't updateable, I'd ask why is CURRENT_USER necessarily a view?
>>
>>(Personally, I would prefer an engine that allows a user to log himself
>>off by means of a simple delete rather than the usual arcane engine
>>plumbing that introduces various environmental commands. That way, the
>>environment is forced to react to db changes rather than the other way
>>around. The engine becomes much simpler if this approach is followed
>>and this is important if there's ever to be any progess in the aspects
>>that today's engines slough off.)
>>...
> > My point, phrased another way, is: given base relvars A, B, and C with > identical headings, this does not make sense: > > (A UNION B) := (B UNION C) > > in the exact same way that this does not make sense: > > int x, y; > x+y := 3;
But computers do solve systems of equations:
x+y = 3
x-y = 1
Received on Sat Aug 29 2009 - 01:29:38 CEST