Re: more on delete from join

From: Mr. Scott <do_not_reply_at_noone.com>
Date: Thu, 3 Sep 2009 00:50:33 -0400
Message-ID: <eqqdnREkNbWH1gLXnZ2dnUVZ_v6dnZ2d_at_giganews.com>


"Marshall" <marshall.spight_at_gmail.com> wrote in message news:badf422a-cd2b-40f1-869b-c0a248363088_at_u36g2000prn.googlegroups.com...

<quote>
I guess I see what you mean, but strictly speaking it doesn't seem to fit the definition. In abductive reasoning, one knows a -> b, and b, but one doesn't know that it was in fact a that implied b. Whereas with a view, we do know.
</quote>

Do we?

For an insert into a union view, one knows a -> c \/ b -> c and c, but one doesn't know whether it was in fact a or b or both that implied c.

For a delete from a join view, one knows ~a -> ~c \/ ~b -> ~c and ~c, but one doesn't know whether it was in fact ~a or ~b or both that implied ~c. Received on Wed Sep 02 2009 - 23:50:33 CDT

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