Historical User and Student Count

SELECT CAST(@TIME_PERIOD_START AS DATE) AS PERIOD_START,
       CAST(@TIME_PERIOD_END AS DATE) AS PERIOD_END,
       c.CLIENT_NAME,
       p.GRP_ID,
       COUNT(DISTINCT u.USR_ID) AS USER_COUNT,
       COUNT(DISTINCT COALESCE(up.CHILD_ID, u.USR_ID)) AS STUDENT_COUNT
FROM CLIENTS c
INNER JOIN CLIENT_PACKAGES cp ON (c.CLIENT_ID = cp.CLIENT_ID)
INNER JOIN PACKAGES p ON (p.GRP_ID = cp.GRP_ID)
INNER JOIN GROUPS g ON (p.GRP_ID = g.GRP_ID)
INNER JOIN
  (SELECT DISTINCT um.USR_ID AS USR_ID,
                                um.GRP_ID AS GRP_ID
   FROM USER_MEMBERSHIPS um
   WHERE ((um.trCTM_Archive = 0
           OR um.trCTM_Archive IS NULL)
          AND (EXISTS
                 (SELECT uma.*
                  FROM USER_MEMBERSHIPS_AUD uma
                  WHERE um.USR_ID = uma.USR_ID
                    AND um.GRP_ID = uma.GRP_ID
                    AND uma.REVTYPE = 0
                    AND uma.EDIT_Date < @TIME_PERIOD_END)
               OR NOT EXISTS
                 (SELECT uma.*
                  FROM USER_MEMBERSHIPS_AUD uma
                  WHERE um.USR_ID = uma.USR_ID
                    AND um.GRP_ID = uma.GRP_ID
                    AND uma.REVTYPE = 0)))
     OR (um.trCTM_Archive <> 0
         AND um.trCTM_Archive IS NOT NULL
         AND (um.trCTM_ArchiveDate IS NULL
              OR (um.trCTM_ArchiveDate >= @TIME_PERIOD_START
                  AND um.trCTM_ArchiveDate < @TIME_PERIOD_END))
         AND NOT EXISTS
           (SELECT uma2.*
            FROM USER_MEMBERSHIPS_AUD uma2
            WHERE uma2.USR_ID = um.USR_ID
              AND uma2.GRP_ID = um.GRP_ID
              AND uma2.REVTYPE = 0
              AND uma2.EDIT_DATE >= @TIME_PERIOD_START
              AND uma2.EDIT_DATE < @TIME_PERIOD_END))) u ON (u.GRP_ID = g.GRP_ID)
LEFT JOIN USER_PARENT up ON (u.USR_ID = up.USR_ID)
WHERE c.CLIENT_NAME NOT LIKE 'Z -%'
  AND c.CLIENT_NAME NOT LIKE 'ZZ%'
  AND c.CLIENT_NAME NOT LIKE 'Z-%'
  AND (g.GRP_ID = :grpid)
GROUP BY c.CLIENT_NAME,
         p.GRP_ID
ORDER BY c.CLIENT_NAME