SELECT
  count(Activity.activityID),
  ExternalUser.fullName,
  ExternalUser.userName
INTO
  :countActivity,
  :fullName,
  :userName 
FROM
  Activity,
  ExternalUser,
  WorkQueueSubscription 
WHERE ExternalUser.userName = WorkQueueSubscription.userName 
  AND Activity.userName = WorkQueueSubscription.userName 
  AND Activity.userName = ExternalUser.userName 
  AND Activity.startDateTime >= :startDateTime 
  AND Activity.endDateTime < :endDateTime 
  AND WorkQueueSubscription.workQueueID = :workQueueID 
  AND Activity.recordStatusCode = :recordStatusCode 
GROUP
  BY ExternalUser.fullName,
  ExternalUser.userName