FIRST and LAST aggregate functions only require one sort
Date: Wed, 21 Mar 2012 18:09:58 -0000
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)
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?
http://www.freelists.org/webpage/oracle-l Received on Wed Mar 21 2012 - 13:09:58 CDT