Re: insert to projection

From: Vadim Tropashko <vadimtro_at_gmail.com>
Date: Sun, 6 Sep 2009 12:20:05 -0700 (PDT)
Message-ID: <753229ad-2676-41aa-a435-eb66564fd6f8_at_m7g2000prd.googlegroups.com>



On Sep 6, 11:40 am, paul c <toledobythe..._at_oohay.ac> wrote:
> If I read that worksheet right, it means we can't delete <p 1, q 'a'>
> from a  conventional table or relvar and expect <p 1> to be negated,
> which I don't argue with.  (whereas I don't think anybody disagrees that
> we already can delete <p 1> and expect <p 1, q 'a'> to be negated.)

What do you mean by negating a tuple? View update expresses increments/ decrements of the base relations in terms of increments/decrements of the view(s). Compare it to (a relatively simple) view maintenance problem where increments/decrements of the view(s) in terms of increments/decrements of the base relations. Maintenance of the projection view (or any other relational expression for that matter) is easy: just take a projection of any incremant/decremant of the base relation. Received on Sun Sep 06 2009 - 14:20:05 CDT

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