Sybase query optimization - sybase

Question

I'm seeing how we can improve the performance of the following sybase query. Currently it takes about 1.5 hrs.
CREATE TABLE #TempTable
(
T_ID numeric,
M_ID numeric,
M_USR_NAME char(10),
M_USR_GROUP char(10),
M_CMP_DATE datetime,
M_CMP_TIME numeric,
M_TYPE char(10),
M_ACTION char(15),
)
select
T.M_USR_NAME,
T.M_USR_GROUP,
T.M_CMP_DATE,
T.M_CMP_TIME,
T.M_TYPE,
T.M_ACTION
from #TempTable T, AUD_TN B
where T.M_ID=B.M_ID
and T.T_ID in
(
select M_NB from TRN H where (M_BENTITY ="KROP" or M_SENTITY = "KROP")
)
UNION
select
A.M_USR_NAME,
A.M_USR_GROUP,
A.M_DATE_CMP,
A.M_TIME_CMP,
A.M_TYPE,
A.M_ACTION
from AUD_VAL A, TRN H
where A.M_DATE_CMP >= '1 May 2012' and A.M_DATE_CMP <= '31 May 2012'
and A.M_ACT_NB0=H.M_NB
and (H.M_BENTITY ="KROP" or H.M_SENTITY = "KROP")
UNION
select
TR.M_USR_NAME,
TR.M_USR_GROUP,
TR.M_DATE_CMP,
TR.M_TIME_CMP,
TR.M_TYPE,
TR.M_ACTION
from TRN_AUD TR, TRN H
where TR.M_DATE_CMP >= '1 May 2012' and TR.M_DATE_CMP <= '31 May 2012'
and TR.M_ACT_NB0=H.M_NB
and (H.M_BENTITY ="KROP" or H.M_SENTITY = "KROP")
DROP table #TempTable
Any help is greatly appreciated. Please note the following
The only table which is not indexed above is AUD_TN
Cheers
RC

Answer 1

Presumably the temporary table is populated, and with a lot of rows?
The temp doesn't need to be indexed but all joins in that part will need to use indexes.
Why not try each part of the UNION separately to find if one of them's slow?
Are you okay using SET SHOWPLAN ON? I think you need to be able to do that as well probably - you need to be able to check that Sybase is using indexes to join right.
TRN BENTITY and SENTITY - indexed? If not your IN is going to be a bit slow, although it might be okay, doing a single table scan into a worktable that Sybase'll index internally. Use an EXISTS instead as well - that might/should work better.
2nd part - both have SARGS (look up in Sybooks if you don't know - search arguments.) I don't know what proportion of rows is found by them but assuming it's a small fraction, you should see an index used on a SARG for whichever table is scanned first, then you should see index join (or perhaps merge join) to the 2nd - but using indexes.
3rd part - similar discussion to the 2nd.
I reckon it'll be the 2nd or 3rd part

Answer 2

How about using cache for these tables. if the query is used kn a regular basis. Its better to get a named cache and bind the tables to it. Also bind the tempdb to cache. This will greatly improve the process execution time. If the temp table is huge then you can create a index on it which may help with performance but i need some more details for that.

Answer 3

If you still have this issue open :
1) Try this at top of sql batch
set showplan on
set noexec on
See if the expected indexes are being picked up by SQL optimizer. If no indexes exist on the columns in where clause, please create one. Create clustered index if possible.
2) In the first query you can replace the subquery in where clause with
create table #T_ID (
M_NB datatype
)
insert into #T_ID
select M_NB from TRN H where (M_BENTITY ="KROP" or M_SENTITY = "KROP")
and modify the where clause as :
where T.M_ID=B.M_ID
and T.T_ID = #T_ID.M_NB