Massive Table - Slow Query - Seeking Effeciency Help

Question

I have a table that has approx 20 columns and anywhere from 4 - 6 million records.
The only columns I am interested in are
ACCOUNT_NUMBER,
SERVICE_CODE,
SERVICE_STATUS
I am looking for customer's (same account number) that have two service codes that are active (status of 'A') that do not have a third service code (no record, or status of 'D').
I am able to obtain results - but the query takes approximately 15 - 20 minutes to complete.
I have tried many variations of obtaining this data....my most current one being
WITH
STEP1 AS
SELECT
S.ACCOUNT_NUMBER
FROM
KAN_CUSTOMER_SERVICES S
WHERE
EXISTS ( SELECT * FROM KAN_CUSTOMER_SERVICES D WHERE D.ACCOUNT_NUMBER = S.ACCOUNT_NUMBER
AND D.SERVICE_CODE = '421'
AND D.SERVICE_STATUS = 'A')
AND S.SERVICE_CODE = '325'
AND S.SERVICE_STATUS = 'A')
SELECT
F.ACCOUNT_NUMBER
FROM
STEP1 F
WHERE
NOT EXISTS ( SELECT * FROM KAN_CUSTOMER_SERVICES E WHERE E.ACCOUNT_NUMBER = F.ACCOUNT_NUMBER
AND E.SERVICE_CODE = '291'
AND E.SERVICE_STATUS = 'A')
I am fairly new to massive tables of a corporation so SQL efficiency is not my strong point.
Any help or insight would be appreciated.
Thanks,
Brett

Answer 1

It looks like a good example for BITMAP Indexes. I would sugest putting one BITMAP Index on each column SERVICE_CODE and SERVICE_STATUS. However Bitmap indexes come at a high cost. They have to be maintained regularily and large INSERT/DELETE operations will suffer in performance. So before you do it, read about it.
The next posibility is to scan the table KAN_CUSTOMER_SERVICES only one time.
Something to get you started (not sure if syntax and logic is correct):
SELECT account_number, count(*), sum(deleted), sum(active_412), sum(active_325)
FROM (
   SELECT account_number,
          case when SERVICE_STATUS = 'D'
               THEN 1 ELSE 0 END CASE deleted
          case when SERVICE_STATUS = 'A' AND SERVICE_CODE = '421'
               THEN 1 ELSE 0 END CASE active_421
          case when SERVICE_STATUS = 'A' AND SERVICE_CODE = '325'
               THEN 1 ELSE 0 END CASE active_325)
GROUP BY account_number
HAVING sum(deleted) = 0
AND sum(active_412) > 0Message was edited by:
Sven Weller