Re[6]: to_number question

From: Jonathan Gennick <jonathan_at_gennick.com>
Date: Mon, 19 Jul 2004 08:39:30 -0400
Message-ID: <726016671.20040719083930@gennick.com>

Monday, July 19, 2004, 8:24:02 AM, Mercadante, Thomas F (thomas.mercadante_at_labor.state.ny.us) wrote:

MTF> Please please please keep distracting us with your unease about how things
MTF> work.  I know I learn a lot reading every single stinkin word you put on
MTF> this list, as well as what you publish.

I'm almost afraid to post this next question, but here goes.

Here's that same old query with a subquery:

SELECT *
FROM ( SELECT flag, TO_NUMBER(num) num

       FROM subtest
       WHERE flag IN ('A', 'C') )

WHERE num > 0;

I can now accept that "num > 0" might be applied to rows that are not returned by the subquery. I have no problem anymore with that happening. I've been converted.

Ok. So. Let's zoom in on the subquery for a moment:

       SELECT flag, TO_NUMBER(num) num
       FROM subtest
       WHERE flag IN ('A', 'C')

If there is no ordering at all to SQL, then do I also need to accept the possibility here that TO_NUMBER(num) might be evaluated for a row in which flag is other than 'A' or 'C'? In other words, can functions in the SELECT list be evaluated on rows *before* those rows have been determined to fall into the result set? Does the SQL standard have anything to say about this particular question?

Best regards,

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

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Received on Mon Jul 19 2004 - 07:36:14 CDT