SELECT
  Activity.activityID,
  Activity.userName,
  Activity.organisationID,
  Activity.subject,
  Activity.activityTypeCode,
  Activity.startDateTime,
  Activity.endDateTime,
  Activity.allDayInd,
  Activity.locationID,
  Activity.locationName,
  Activity.priorityCode,
  Activity.timeStatusCode,
  Activity.notes,
  Activity.recurrenceID,
  Activity.caseID,
  Activity.concernRoleID,
  Activity.recordStatusCode
INTO
  :activityID,
  :userName,
  :organisationID,
  :subject,
  :activityTypeCode,
  :startDateTime,
  :endDateTime,
  :allDayInd,
  :locationID,
  :locationName,
  :priorityCode,
  :timeStatusCode,
  :notes,
  :recurrenceID,
  :caseID,
  :concernRoleID,
  :recordStatusCode 
FROM
  Activity,
  CaseHeader 
WHERE 
  (
    CaseHeader.caseID = :caseID 
    AND Activity.caseID = CaseHeader.caseID 
  ) 
  AND 
  (
    
    (
      Activity.startDateTime >= :fromDate 
      AND Activity.startDateTime <= :toDate 
    ) 
    OR 
    (
      Activity.startDateTime < :fromDate 
      OR Activity.startDateTime IS NULL 
    ) 
  )