Re[2]: to_number question

Jonathan Gennick <jonathan@xxxxxxxxxxx> · Thu, 15 Jul 2004 08:50:50 -0400

Thursday, July 15, 2004, 8:08:04 AM, Stephen.Lee@xxxxxxxx 
(Stephen.Lee@xxxxxxxx) wrote:
SLDC> I believe the purpose of the subquery was to "request
SLDC> it". The function was being applied to data that was
SLDC> not in the subquery. If this is part of the laws of
SLDC> SQL processing, "then the law is an ass". I'm more
SLDC> inclined to say that this is a bug.

Stephen's original problem and Tanel's solution are
fascinating. I can see where the optimizer might try and
combine Stephen's main query and subquery into just one query.
However, it seems to me that an optimization should *never*
return different results from the original operation that is
being optimized.

This begs the question of how the optimizer should decide
whether it's safe to merge a subquery and main query.
Clearly, the optimizer seems to have made the wrong call
in the case of the query we've been talking about.

I wish I had more time to spend thinking about all this, but
I've got to get to work for the day.

Best regards,

Jonathan Gennick --- Brighten the corner where you are
http://Gennick.com * 906.387.1698 * mailto:jonathan@xxxxxxxxxxx

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