The following query is performing poorly in the app. I have tried the
scalar subquery approach (using formatted to_char)  with no luck. any
help would be appreciated.

SELECT  MP_NO, MP_DESC, MP_ACTIVE AS "FLAG_YES_NO",
(
  ( SELECT COUNT(*)     FROM ST, STINV
                WHERE ST.ST_ID = STINV.ST_ID
                AND ST.ST_POSTED IS NOT NULL
                AND STINV.MP_NO = MPT.MP_NO )
   +
  ( SELECT COUNT(*) FROM PT, PTINV
                  WHERE PT.PT_ID = PTINV.PT_ID
                  AND PT.PT_POSTED IS NOT NULL
                  AND PTINV.MP_NO = MPT.MP_NO  )
)
FROM MPT
WHERE COMP_ID = 1
GROUP BY MP_NO, MP_DESC, MP_ACTIVE

Thanks,