FIRST and LAST aggregate functions only require one sort
Date: Wed, 21 Mar 2012 18:09:58 -0000
Message-ID: <BA8B8CB827554A248DD09FE4660121A6_at_VMGENERAL>
Hi Guys and Gals,
This is my first post here so here goes:
I came across the need to use the FIRST and LAST aggregate functions. This is, in fact, the first time that I have remembered of their existence when the need arose!
When I looked at the execution plan I saw something I didn't expect. This is the basic statement:
SELECT MIN (c1) KEEP (DENSE_RANK FIRST ORDER BY c2)
,MAX (c3) KEEP (DENSE_RANK LAST ORDER BY c4)
FROM t1;
Now the curious thing is that the execution plan shows only one sort! Indeed, the number of sorts remains the same no matter how may different ORDER BY columns I use.
Does anybody have any idea how Oracle does it or whether it actually does some hidden sorts that it isn't telling us about?
--Tony Hasler
--
http://www.freelists.org/webpage/oracle-l
Received on Wed Mar 21 2012 - 13:09:58 CDT