count(*) 计算下井次数

Question

select distinct e.name,d.name,
sum(case when datediff(hour,a.inTime,a.outTime)>2 then 1
         when 2<datediff(hour,a.inTime,a.outTime)<12 then 1.5
         when datediff(hour,a.inTime,a.outTime)>12 then 2
         else 0
    end)as 下井次数from attendance a ,employee e,department dwhere a.cardNum=e.cardnumber and d.id=e.departmentId
and a.occDay between 20131213 and 20131222 
--and datediff(hour,a.inTime,a.outTime)>2
group by e.name,d.name