Re: MAX/MIN optimization via rewrite (plus query rewrites generally)

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От Jim C. Nasby
Тема Re: MAX/MIN optimization via rewrite (plus query rewrites generally)
Дата
Msg-id 20041111041734.GB56660@decibel.org
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Ответ на MAX/MIN optimization via rewrite (plus query rewrites generally)  (Mark Kirkwood <markir@coretech.co.nz>)
Ответы Re: MAX/MIN optimization via rewrite (plus query rewrites  (Mark Kirkwood <markir@coretech.co.nz>)
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On Thu, Nov 11, 2004 at 11:48:49AM +1300, Mark Kirkwood wrote:
> I am looking at implementing this TODO item. e.g. (max case):
> 
> rewrite
> SELECT max(foo) FROM bar
> as
> SELECT foo FROM bar ORDER BY foo DESC LIMIT 1
> if there is an index on bar(foo)
Out of curiosity, will you be doing this in such a way that 

SELECT min(foo), max(foo) FROM bar

will end up as

SELECT (SELECT foo FROM bar ORDER BY foo ASC LIMIT 1), (SELECT ... DESC
LIMIT 1)

?
-- 
Jim C. Nasby, Database Consultant               decibel@decibel.org 
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