RE: More on Subquery Madness

From: Wolfgang Breitling <breitliw_at_centrexcc.com>
Date: Mon, 27 Sep 2004 11:38:41 -0700
Message-ID: <1096310321.41585e31e2cf9@webmail.hosting.telus.net>

Me thinks so too.
But then I have a problem with this entire "order of execution" argumentation. E.F.Codd set out specifically to exclude any procedural thinking, any "how" thinking from his relational model. All one should be concerned with is to describe the "what", the resultset.
I am coming back to using NULL for undefined/unanswerable predicates such as "to_number" of an argument that does not represent a number or
"the radius of an ellipsis" if it is truly an ellipsis and not a circle

If you take that route then the order of the restrictions does not matter and either path yields the same resultset, which is all that matters.

Quoting Justin Cave <justin_at_askddbc.com>:

> Reading Date's two replies, it seems that he reaches the opposite conclusion
> in the later discussion-- SQL is unable to express certain relational
> algebra concepts properly-- than he did originally-- Oracle's optimizer is
> behaving incorrectly. I don't see him say that he has changed his mind,
> though... Am I missing some subtlety here?
>
> Justin Cave
> Distributed Database Consulting, Inc.
> http://www.ddbcinc.com/askDDBC

-- 
regards

Wolfgang Breitling
Oracle 7,8,8i,9i OCP DBA
Centrex Consulting Corporation
www.centrexcc.com

--
http://www.freelists.org/webpage/oracle-l

Received on Mon Sep 27 2004 - 13:34:17 CDT