# Re: Extending my question. Was: The relational model and relational algebra - why did SQL become the industry standard?

Date: Thu, 13 Feb 2003 16:54:15 -0800

Message-ID: <jcX2a.16$O%2.38_at_news.oracle.com>

"Bob Badour" <bbadour_at_golden.net> wrote in message
news:4uW2a.1409$0G3.168661119_at_mantis.golden.net...

> "Mikito Harakiri" <mikharakiri_at_ywho.com> wrote in message

*> news:irT2a.10$O%2.40_at_news.oracle.com...
**> > Not
**> > for aggregates:
**> >
**> > PROJECTION*AGGREGATE != AGGREGATE*PROJECTION
**> >
**> > for example
**> >
**> > select distinct S from (
**> > select distinct SUM(SAL) from emp
**> > )
**> >
**> > is not the same as
**> >
**> > select distinct SUM(SAL) from (
**> > select distinct SAL from emp
**> > )
**> >
**> > where i'm using SQL with the "distinct" keyword merely as a surrogate
*

for

> > true relational syntax ("distinct" is redundant after aggregate

operation,

> > of course).

*>
**> Why should the sum of all salaries equal the sum of distinct salaries?
*

is the same as

select SUM(SAL) from (

Once again, this means that PROJECTION and AGGREGATE commute in the bag model. Received on Fri Feb 14 2003 - 01:54:15 CET