Index on multiple columns issue Oracle 9i

Question

Hi,
I have a couple of issues and would appreciate it if anyone can help:
a). I have a table that has indexes on multiple columns, so for example:
Index 1 on Org_Type, Org_Id and Effdt
Index 2 on FICE_CD, Org_Id and Effdt etc.
I have 9 such indexes and all of them hav Effdt in it.
My question is if I query the table and always use a subquery to get the max Effdt rows form the table, will the above indexes help in my query or will I have to create another index just on Effdt so that my Query runs faster.
b). I have a target table with more than 20 million rows in it. This table has an Effdt too and I would like to find the max effdted row in this table as well so that I can then use that date-time stamp in my ETL tool to do an incremental update from my source table each night. But since the amount of rows is huge, my query runs forever. I have a normal non-unique index on Effdt. Is there another way I can optimize this table? Currenlty I have resorted to getting all rows from source that are >= (sysdate -1), but I would prefer to get the max date-time stamp from the target table itself.
Thanks,
CJ

Answer 1

Hi ,
Thanks for the input. I just used the explain plan and found that there is a full table scan happening on the PS_EXT_ORG_TBL, so I guess I will have to create an index specifically on the effdt field. The sql is as follows:
Select E.EMPLID, E.INSTITUTION, E.EXT_ORG_ID, E.EXT_CAREER, E.EXT_DATA_NBR, E.EXT_SUMM_TYPE, E.UNT_ATMP_TOTAL, E.UNT_COMP_TOTAL,
E.CLASS_RANK, E.CLASS_SIZE, E.PERCENTILE, E.UM_GPA_EXCLUDE, E.UM_EXT_ORG_GPA, E.CONVERT_GPA,
E.UM_EXT_ORG_CNV_CR, E.UM_EXT_ORG_CNV_GPA, E.UM_EXT_ORG_CNV_QP, E.UM_GPA_OVERRIDE, E.EXT_ACAD_LEVEL,
F.FROM_DT, F.TO_DT, G.EXT_DEGREE_NBR, G.DEGREE, G.DESCR "DEGREE DESCR", G.DEGREE_DT, H.EFFDT,
H.EFF_STATUS, H.SCHOOL_CODE, H.LS_SCHOOL_TYPE, H.ATP_CD, H.CITY, H.STATE, H.COUNTRY,
H.DESCR "SCHOOL DESCR", H.PROPRIETORSHIP
FROM PS_EXT_ACAD_SUM E, PS_EXT_ACAD_DATA F, PS_EXT_DEGREE G, PS_EXT_ORG_TBL H
WHERE E.EXT_ORG_ID = F.EXT_ORG_ID AND E.EMPLID = F.EMPLID
AND E.EXT_ORG_ID = G.EXT_ORG_ID AND E.EMPLID = G.EMPLID
AND E.EXT_ORG_ID = H.EXT_ORG_ID
AND H.EFFDT=(SELECT MAX(EFFDT) FROM PS_EXT_ORG_TBL H1
          WHERE H.EXT_ORG_ID=H1.EXT_ORG_ID
                    AND H.EFF_STATUS=H1.EFF_STATUS
                    AND H.SCHOOL_CODE=H1.SCHOOL_CODE
                    AND H.LS_SCHOOL_TYPE=H1.LS_SCHOOL_TYPE
                    AND H.ATP_CD=H1.ATP_CD
                    AND H.CITY=H1.CITY
                    AND H.STATE=H1.STATE )
My source DB is a copy of the transactional database, so there is no danger of new rows coming in.