partition by 用法

SELECT B .部门, B. 用户,  COUNT(A .user_name) AS 处理次数,
               SUM(COUNT (A. user_name)) over(partition by B.部门 ) as 部门处理次数 FROM wf_task_process_info_2 A
              JOIN TEMP B on A .user_name= B.用户名
       WHERE A .time between @begin and @end
       GROUP BY B. 部门, B.用户