Optimizer do not use right INDEX

Hi,
I'm sending this again because i'm very confused :
This Query :
SELECT 0
FROM
WOTransit -- with (index=x1,readuncommitted)
INNER JOIN WO On WoTransit.Wo_ref=Wo.Wo_ref
WHERE WO.Cmd_No=814352
AND ISNULL(WOTransit.Charge_ref,0) <> 0
Since this morning this query is much more slow than usual
If i add : "with (index=x1,readuncommitted) ", the speed
is back to normal. because optimiser normaly use that
index.
If not, optimizer is using the clustered index X2 (with
full scan ...:o( ) that is not related to the query.
why doesn't he use the right index ?
What can i do to fix that ? i allready :
- ran UPDATEUSAGE and no change.
- droped created index X1. no change
- reran UPDATEUSAGE and no change.
- Updatstats has been ran earlyer this morning
I don't want to drop create X2 now because i'm in
production and i will block every one for at least an hour.
Please, some help
Thank you !
DonaldPls see my response to your other post.
Peter Yeoh
http://www.yohz.com
Need smaller SQL2K backup files? Try MiniSQLBackup
"Donald" <anonymous@.discussions.microsoft.com> wrote in message
news:1c43c01c45239$c4001610$a401280a@.phx
.gbl...
> Hi,
> I'm sending this again because i'm very confused :
> This Query :
> SELECT 0
> FROM
> WOTransit -- with (index=x1,readuncommitted)
> INNER JOIN WO On WoTransit.Wo_ref=Wo.Wo_ref
> WHERE WO.Cmd_No=814352
> AND ISNULL(WOTransit.Charge_ref,0) <> 0
>
> Since this morning this query is much more slow than usual
> If i add : "with (index=x1,readuncommitted) ", the speed
> is back to normal. because optimiser normaly use that
> index.
> If not, optimizer is using the clustered index X2 (with
> full scan ...:o( ) that is not related to the query.
> why doesn't he use the right index ?
> What can i do to fix that ? i allready :
> - ran UPDATEUSAGE and no change.
> - droped created index X1. no change
> - reran UPDATEUSAGE and no change.
> - Updatstats has been ran earlyer this morning
> I don't want to drop create X2 now because i'm in
> production and i will block every one for at least an hour.
> Please, some help
> Thank you !
> Donald
>