Re: Transitive Closure
From: Alfredo Novoa <alfredo_at_ncs.es>
Date: 16 May 2004 05:57:23 -0700
Message-ID: <e4330f45.0405160457.37da2e49_at_posting.google.com>
Date: 16 May 2004 05:57:23 -0700
Message-ID: <e4330f45.0405160457.37da2e49_at_posting.google.com>
"Mikito Harakiri" <mikharakiri_at_iahu.com> wrote in message news:<l%bpc.34$7Q3.118_at_news.oracle.com>...
> How about TC not commuting with selection?
>
> TC( select x,y from {(x=1,y=2),(x=2,y=3)} where x=1 and y=3)
>
> is not the same as
>
> select x,y from TC( {(x=1,y=2),(x=2,y=3)}) where x=1 and y=3
TC(A where b) <> TC(A) where b
TC is not associative in respect to restriction.
There are many non associative operators in respect to others.
(2 * 0) + 1 <> (2 + 1) * 0
Regards
Alfredo
Received on Sun May 16 2004 - 14:57:23 CEST