SELECT cso.F_Key, cso.F_ServiceType,cso.F_ASPNode,cso.F_Productline,cso.F_InternalCloseTime,
    case WHEN F_InternalCloseTime>nvl(F_ComplaintTime,to_date('1900-01-01','yyyy-mm-dd')) THEN F_InternalCloseTime
  ELSE nvl(F_ComplaintTime,to_date('1900-01-01','yyyy-mm-dd')) end MAXTime
 FROM cr_cs_cso cso
  left join CR_C_RewardPunishRecord rpd on rpd.f_cso = cso.f_key
  left join CR_C_RewardPunishCriteria rpc on rpc.f_key = rpd.f_RewardPunishCriteria
  WHERE 1=1 and rpd.f_status =50 and rpc.f_code in ('HTF01','HTF02','HTF03','HTF05','HTF06','HTF08','HTF09','HTF10','HTF13')
  AND F_Priority IS NOT NULL
  AND F_ComplaintType IS NOT NULL
  AND F_ComplaintTime IS NOT NULL
  AND (F_ComplaintType IN (4003,4006,4007,4008,4005,4009,4019,4034,4030,4029,4018) or F_Priority IN (70,60))
  AND cso.F_Status in (160,170,180)
  and ((F_InternalCloseTime>isnull(F_ComplaintTime,to_date('1900-01-01','yyyy-mm-dd'))
        and F_InternalCloseTime BETWEEN to_date('2012-06-27','yyyy-mm-dd') AND to_date('2012-07-26 23:59:59','yyyy-mm-dd hh24:mi:ss'))
    or (
        isnull(F_ComplaintTime,'1900-1-1') BETWEEN to_date('2012-06-27','yyyy-mm-dd') AND to_date('2012-07-26 23:59:59','yyyy-mm-dd hh24:mi:ss')
    ))
  and rpd.f_yearmonth='2012-07'

------解决方案--------------------
isnull 改成nvl
SELECT Cso.f_Key,
      Cso.f_Servicetype,
      Cso.f_Aspnode,
      Cso.f_Productline,
      Cso.f_Internalclosetime,
      CASE
        WHEN f_Internalclosetime > Nvl(f_Complainttime, '1900-1-1') THEN
         f_Internalclosetime
        ELSE
         Nvl(f_Complainttime, '1900-1-1')
      END Maxtime
 FROM Cr_Cs_Cso Cso
 LEFT JOIN Cr_c_Rewardpunishrecord Rpd ON Rpd.f_Cso = Cso.f_Key
 LEFT JOIN Cr_c_Rewardpunishcriteria Rpc ON Rpc.f_Key =
                                            Rpd.f_Rewardpunishcriteria
  WHERE 1 = 1
  AND Rpd.f_Status = 50
  AND Rpc.f_Code IN ('HTF01', 'HTF02', 'HTF03', 'HTF05', 'HTF06',
       'HTF08', 'HTF09', 'HTF10', 'HTF13')
  AND f_Priority IS NOT NULL
  AND f_Complainttype IS NOT NULL
  AND f_Complainttime IS NOT NULL
  AND (f_Complainttype IN
      (4003, 4006, 4007, 4008, 4005, 4009, 4019, 4034, 4030, 4029, 4018) OR
      f_Priority IN (70, 60))
  AND Cso.f_Status IN (160, 170, 180)
  AND CASE WHEN
  f_Internalclosetime > Nvl(f_Complainttime, '1900-1-1') THEN f_Internalclosetime ELSE Nvl(f_Complainttime, '1900-1-1') END AND f_Internalclos