hello.
I'm working on optimisations problems frequently,
and since the V12 of sybase, I tried to implement sort_merge options on many Query,
but I'n never see it working very well, I tried all recommandations of
sybase (configure number of sort buffer, etc ...).
In many case Sybase choose showplan with sort_merge but even if
it's better in i/o, in time it worst(and very worst !).
Does anyone succeed in working with these sort_merge?
Stéphane.

Merge joins are not always ways faster than classic nested-loop joins;
as you've noticed, they're sometimes even slower.
In my experience, merge joins are most likely to be faster in cases
where two tables are joined on identical columns, on which indexes are
present. For example, table1 has an index on columns (a,b), as does
table2. When doing a join on these columns, you'll probably see that a
merge join is faster.

HTH,

Rob
-------------------------------------------------------------
Rob Verschoor

Certified Sybase Professional DBA for ASE 12.5/12.0/11.5/11.0
and Replication Server 12.5

Author of "Tips, Tricks & Recipes for Sybase ASE" and
"The Complete Sybase ASE Quick Reference Guide"
Online orders accepted at http://www.sypron.nl/shop

mailto:rob@DO.NOT.SPAM.sypron.nl.REMOVE.THIS.DECOY
http://www.sypron.nl
Sypron B.V., P.O.Box 10695, 2501HR Den Haag, The Netherlands
-------------------------------------------------------------

"stephane" <stephane.lehebel@bnpparibas.com> wrote in message
news:220aebda.0309020705.7a73cd3d@posting.google.c om...
> hello.
> I'm working on optimisations problems frequently,
> and since the V12 of sybase, I tried to implement sort_merge options
on many Query,
> but I'n never see it working very well, I tried all recommandations
of
> sybase (configure number of sort buffer, etc ...).
> In many case Sybase choose showplan with sort_merge but even if
> it's better in i/o, in time it worst(and very worst !).
> Does anyone succeed in working with these sort_merge?
> Stéphane.