Laura,
Unfortunately it's hard to provide advice without knowing a lot more about
the tables, the cardinality of the columns in the where clause, and perhaps
even whether there are tricks we might be able to abuse by knowing
information about the data that's not immediately obvious.
Ignoring that, an explain plan (as requested by Connor) will certainly
help. Other things that would help are row counts of each table, and for
the columns in the where clause what is there selectivity like.
One way to determine selectivity would be something like:
select count(*) total_rows,
sum(decode(pre_approved_purch_flag, 'N', 1, 0)) pre_app_is_n,
sum(decode(company_reimburse_flag, 'Y', 1, 0)) com_reim_is_y,
sum(decode(pre_approved_purch_flag||company_reimburse_flag, 'NY', 1,
0)) both_cond_met
from part_master_catalogs
This will give an idea of how many rows meet each criteria, and how many
meet both criteria. This may then give some hint as to whether an index
access path is worthwhile or whether a full table scan is quicker. Is
there a magic figure to determine which is faster? No. But the extremes
(like 1% and 90%) will be obvious.
With regard to your specific query, I would ensure that the subselect
performs very fast since it is probably being called in some kind of nested
loop. Since some of the columns in the subselect aren't prefixed with a
table alias I can't even work out which table they necessarily come from.
Regards,
Mark.
"Burton, Laura
L." To: Multiple recipients of list ORACLE-L
<[EMAIL PROTECTED]>
<[EMAIL PROTECTED] cc:
plus.com> Subject: Select Statement Gone South??
Sent by:
[EMAIL PROTECTED]
om
26/02/2003
12:23
Please respond
to ORACLE-L
I am inserting records into a table based on a select statement and it is
taking way too much time. I have created indexes of the foreign keys and
tried to rearrange the where clause to omit records earlier, but to no
avail. The statement looks like this:
Insert into table test
select part_num,
nomenclature,
to_char(requisition_date,'yddd')
||lpad(preq.document_serial,4,0),
2, /* '53-Purchase' */
PSA.TRANS_date,
requisition_qty,
unit_price,
4 /* 'ALMD Disapproval' */
from part_master_catalogs pmc,
part_requisitions preq,
part_price_histories pph,
part_status_assocs psa
where preq.pmc_id_fk = pmc.pmc_id
and preq.preq_id = psa.preq_id_fk
and psa.req_status_cd_fk = 'D'
AND PSA.TRANS_DATE <= TO_DATE('&&NEWMEDATE','MM-DD-YYYY')
AND PSA.TRANS_DATE > TO_DATE('&&LASTMEDATE','MM-DD-YYYY')
and pmc.pre_approved_purch_flag = 'N'
and pmc.company_reimburse_flag = 'Y'
and pph.pph_id = (select max(pph_id) from part_price_histories
where preq.pmc_id_fk = pmc_id_fk
and requisition_date >= effective_date)
Any ideas?? Any insight would be appreciated.
Thanks,
Laura
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