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From Matt Solnit <msol...@soasta.com>
Subject Re: Unable to group by certain functions
Date Fri, 06 Mar 2009 01:47:20 GMT
> > ij> SELECT ABS(a) FROM foo GROUP BY ABS(a);
> >
> > works fine.  But if I use CEIL or FLOOR, I get an error:

> I'm truly speculating here, but I wonder if this behavior is
> because CEIL and FLOOR return floating point values, and therefore
> have a certain amount of inexactness in them, which is unacceptable
> for GROUP BY processing?

Hi Bryan.  Thanks for your response.  This precisely one of the subjects
that were debated in the 2006 thread
(http://markmail.org/message/pggvaqh6ejg2dtf3).  Here are some snippets:

Daniel Debrunner:  "Grouping by DOUBLE should be allowed since they can be
compared. It's probably not advisable, but Derby's SQL should allow it."

Bernt Johnsen:  "A double is just a finite set of bits ... so it should
work, even if it is not the most reasonable thing to do."

And of course, it works fine in MySQL and PostgreSQL ;-).

> I'm afraid all I can really do is to confirm that I see the
> same behavior that you see, and it doesn't appear to be random,
> but rather is intentional, and has to do with the fact that CEIL
> and FLOOR are implemented differently than ABS.

What's next?  Should I submit an issue to JIRA?

> bryan


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