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Rob, in your samples you didn't have any selection criteria (no WHERE
clause). You were fetching more than 20% of the rows (in fact, you are
fetching 100% of the rows) so table scan is the best option (or index scan
in your index-only-access scenario).
If you add selection criteria to your example to select less than 20% of the
rows, difference would not be measured in milliseconds, but probably seconds
or minutes (if it takes that long for it to complete).
Elvis
Celebrating 11-Years of SQL Performance Excellence on IBM i5/OS and OS/400
www.centerfieldtechnology.com
A little. I just replied in a different post that I just used VE to
modify some sql to go from using a table scan to a index scan and shaved a
few milliseconds off of a sql statement. That's the kind of stuff that it
might be useful for. But then again, you have to know that table scans
"may" not be the most efficient item out there.
Hey a few milliseconds may not be much. Then again, my sample may be
peanuts.
Rob Berendt
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