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Re: Teach SELECT DISTINCT first!

From: Laconic2 <laconic2_at_comcast.net>
Date: Wed, 28 Apr 2004 08:08:18 -0400
Message-ID: <GJqdnT5LYtHnAxLdRVn-jw@comcast.com>


Robert,

Thanks very much for posting this. It's worth reading.

If we could all agree on the difference between a LIST and a SET, we'd be better off.

"robert" <gnuoytr_at_rcn.com> wrote in message news:da3c2186.0404271241.a427ea5_at_posting.google.com...
> "Laconic2" <laconic2_at_comcast.net> wrote in message
news:<XJadna5ZoOR58xPdRVn-jg_at_comcast.com>...
> > Thanks. I didn't know that about Date pontificating. I don't read that
> > much Date.
> >
> > That's really what I was driving at, a little while ago, when I said
that
> > SQL had made an unfortunate choice in the meaning of "SELECT"
> >
> > My thought is that, if SQL had originally made "SELECT" default to
"SELECT
> > DISTINCT" instead of "SELECT ALL", there would be less misunderstanding
of
> > the RDM than there is.
> >
> > But I was declared "orthogonal".
> >
> > Note that, when it came to "UNION" SQL defaulted to "UNION DISTINCT",
and
> > if you want "UNION ALL", you have to say "UNION ALL".
> >
> > I claim, without proof, that a really good optimizer can tell, by
using
> > rules of logic, and perhaps more metadata than is now stored, when
"SELECT
> > ALL" and "SELECT DISTINCT" will produce the same result. If so, it
can
> > skip a step, and thereby speed things up.\
>
> i'm way too lazy to type all this in (or take credit for it).
>
>

http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=UTF-8&threadm=c0d87ec0.0202240850.428d7b88%40posting.google.com&rnum=12&prev=/groups%3Fq%3D%252B%2522select%2Bdistinct%2522%2B%252Bdate%2B%2Bgroup:comp.databases.theory%26start%3D10%26hl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26group%3Dcomp.databases.theory%26selm%3Dc0d87ec0.0202240850.428d7b88%2540posting.google.com%26rnum%3D12
>
> if one wishes not to read it: Celko cites Codd and Date in arguing
> against
> dups. i concur.
Received on Wed Apr 28 2004 - 07:08:18 CDT

Original text of this message

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