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Re: Why using "Group By"

From: Bob Badour <bbadour_at_golden.net>
Date: Thu, 13 Mar 2003 16:49:54 -0500
Message-ID: <Qv7ca.1$QY2.123001@mantis.golden.net>


"Mikito Harakiri" <mikharakiri_at_ywho.com> wrote in message news:JG6ca.18$wV5.85_at_news.oracle.com...
>
> "oferbu" <junkbu_at_hotmail.com> wrote in message
> news:b9b409f2.0303130207.42f8ab91_at_posting.google.com...
> > Hello All,
> >
> > This is a theoretical question. Why do I need to add the "Group By" in
> > the following SQL:
> >
> > SELECT
> > CUSTOMER_CITY, COUNT(*)
> > FROM
> > CUSTOMER_TABLE
> >
> > Isn't it clear that I want to get the number of rows per city, so why
> > is it necessary to add:
> >
> > GROUP BY
> > CUSTOMER_CITY
> >
> > I mean to say that those added lines didn't give more information, and
> > any resonable person (or a good sql parser...) could have understand
> > what I really want at the first sql.
>
> One more reason: you can omit aggregate and emulate "distinct" like this
>
> select empno, name, sal, deptno from emp
> group by empno, name, sal, deptno
>
> Therefore, either "distinct" is redundant as we can express it via "group
> by" or, alternatively, "group by" is redundant and can be expressed via
> corellated scalar subquery in the select clause, but we need "distinct"
> then. I wonder what theoretical reason behind this fact is.

Assuming logical identity, both distinct and group by are superfluous. Received on Thu Mar 13 2003 - 15:49:54 CST

Original text of this message

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