Re: more on delete from join

From: Bob Badour <>
Date: Sat, 29 Aug 2009 11:45:32 -0300
Message-ID: <4a993f13$0$23766$>

Kevin Kirkpatrick wrote:

> On Aug 28, 6:29 pm, Bob Badour <> wrote:

>>Kevin Kirkpatrick wrote:
>>>On Aug 28, 4:32 pm, paul c <> 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
> Well, I will grant that.   But there is an difference between
> exp[0]:='x+y = 3'
> exp[1]:='x-y = 1'
> print(Solve_system (exp, 'x')); -- prints 2
> and
> x+y := 3;
> x-y := 1;
> print (x);  -- prints 2? (does it? can it? see below...)

I agree. The former is klunky and inelegant while the latter is elegant and clear. Received on Sat Aug 29 2009 - 16:45:32 CEST

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