Why does this query run slow ??

Question

hi ,
i have the following query
SELECT
  PT.PT_ID,
  PCD_INST.CALL_PCD_NAME,
  RC.RC_ID,
  RC.RC_TITLE,
  PCD.PCD_TITLE,
  RC.E_TYPE
FROM
  PT,
  PCD_INST,
  RC,
  PCD,
  PCD_INST_RS
WHERE
  ( PT.PT_ID = PCD_INST.PCD_ID  )
  AND  ( PCD.PCD_ID = PCD_INST_RS.PCD_ID  )
  AND  ( (RC.RC_NAME = PCD_INST_RS.RC_NAME) AND (RC.RC_ACTIVE_FLAG = 'A')  )
  AND  ( (PCD.PCD_ID LIKE PCD_INST.CALL_PCD_NAME || '.%') AND (PCD.PCD_AFLAG = 'A')  )
  AND  (
  ( PT.PT_AFLAG = 'A'  )
  AND  ( PT.OBS_FLAG <> 'Y'  )
  AND  ( PCD.PCD_AFLAG = 'A'  )
  AND  ( PCD.OBS_FLAG <> 'Y'  )
  AND  ( RC.RC_AFLAG = 'A'  )
  AND  ( RC.OBS_FLAG <> 'Y'  )
  AND   TO_NUMBER (PCD_INST.INST_NUM)  =  123
  AND  ( PCD_INST_RS.H = 'Y'  )
  AND  ( PCD_INST_RS.MP = 'Y'  )
  AND  PT.PSTATUS  =  'A')and the execution plan
Execution Plan
   0      SELECT STATEMENT Optimizer=CHOOSE (Cost=228 Card=1 Bytes=205
   1    0   TABLE ACCESS (BY INDEX ROWID) OF 'PCD_INST' (Cost=
          2 Card=136 Bytes=4352)
   2    1     NESTED LOOPS (Cost=228 Card=1 Bytes=205)
   3    2       MERGE JOIN (CARTESIAN) (Cost=227 Card=3 Bytes=519)
   4    3         TABLE ACCESS (BY INDEX ROWID) OF 'PCD_INST_RS'
                 (Cost=4 Card=1 Bytes=41)
   5    4           NESTED LOOPS (Cost=141 Card=1 Bytes=143)
   6    5             MERGE JOIN (CARTESIAN) (Cost=57 Card=28 Bytes=28
          56)
   7    6               TABLE ACCESS (BY INDEX ROWID) OF 'RC' (Cos
          t=2 Card=1 Bytes=52)
   8    7                 INDEX (RANGE SCAN) OF 'RC_IDX1' (NON
          -UNIQUE) (Cost=1 Card=1)
   9    6               BUFFER (SORT) (Cost=55 Card=65 Bytes=3250)
  10    9                 TABLE ACCESS (BY INDEX ROWID) OF 'PCD' (Cos
          t=56 Card=65 Bytes=3250)
  11   10                   INDEX (RANGE SCAN) OF 'PCD_IDX_1' (NON
          -UNIQUE) (Cost=30 Card=25944)
  12    5             INDEX (RANGE SCAN) OF 'PCD_INST_RS
          _PK' (UNIQUE) (Cost=3 Card=233)
  13    3         BUFFER (SORT) (Cost=223 Card=165 Bytes=4950)
  14   13           TABLE ACCESS (FULL) OF 'PART' (Cost=86 Card=165 By
          tes=4950)
  15    2       INDEX (RANGE SCAN) OF 'PCD_INST_PK' (UNIQUE) (
          Cost=2 Card=1)what would you suggest so the performance can be much better ?
or anything that i shld take note from the execution plan ?
current it took > 4 hrs to retrieve abt 300 - 400k records
tks & rdgs

Answer 1

Probably all the additional brackets in the where
clause.
Just kidding, but it would help to see what is
happening better if you got rid of them, e.g.
WHERE
( PT.PT_ID = PCD_INST.PCD_ID  )
AND  ( PCD.PCD_ID = PCD_INST_RS.PCD_ID  )Should be
WHERE
PT.PT_ID = PCD_INST.PCD_ID 
AND   PCD.PCD_ID = PCD_INST_RS.PCD_ID  You could remove the to_number
AND   PCD_INST.INST_NUM  =  '123'
anything that i shld take note from the executionplan ?
What is shld?
retrieve abt 300 - 400k recordsHow many is abt?
SELECT STATEMENT Optimizer=CHOOSE (Cost=228Card=1 Bytes=205)Optimizer thinks it is going to return 1 row so your
statistics are way off.
What is rdgs?hi ,
i'll first remove the bracket and the to_number and try
then
i'll check with the DBA to see if the stats are up to date
sorry for the short-form, i was reminded earlier not to use that but i forgot
shld --> should
rdgs --> regards