Question

我有一个需要编写的查询。实验室助理将输入实验室寻求帮助的学生的信息。该领域是：

Visit_ID，Student_ID，Visit_Date，Time_In，Time_Out，Course，Asst_ID。

time_in条目有3个会话

Session 1 9-12
Session 2 12-3
Session 3 3-6

查询需要确定当天哪个会话访问者最多。这就是我到目前为止所做的：

with cte as
 (
  select 
      case
        when cast(Time_In as time) >'12:00:00' and cast(Time_In as time) <='15:00:00'  and Visit_Date = cast(GETDATE() as date)then 'Session 2' 
        when cast(Time_In as time) >'3:00:00' and cast(Time_In as time)<= '6:00:00' and Visit_Date = cast(GETDATE() as date) then 'Session 3'
        else 'Session 1'
      end session
      /*course*/
    from Lab_Visits2
  ), ctecnt as (
  select session,/* course,*/ count(*) cnt
  from cte
  group by session /*course*/
)
select session, /*course,*/ (cnt)
from (
  select session, /*course,*/ cnt, row_number() over (order by cnt desc) rn
  from ctecnt
  ) t
where rn = 1

SQL，使用输入的时间查找与大多数访问者的会话

0 个答案: