需要以用户数量为先来拆分入口点

Question

+------------+-------+---------+---------------+
| STudent_ID | Marks | Subject | EntryPoints   |
+------------+-------+---------+---------------+
|          1 |    50 | Maths   |          10   |
|          2 |    50 | Maths   |          10   |
|          3 |    45 | Maths   |          10   |
|          1 |    30 | History |          20   |
|          2 |    30 | History |          20   |
|          3 |    30 | History |          20   |
+------------+-------+---------+---------------+

预期输出：

+------------+-------+---------+---------------+ 
| student_id | Marks | Subject | TotalPoints   | 
+------------+-------+---------+---------------+ 
|          1 |    50 | Maths   | 5             | 
|          2 |    50 | Maths   | 5             | 
|          1 |    30 | History | 6.66          | 
|          2 |    30 | History | 6.66          | 
|          3 |    30 | History | 6.66          | 
+------------+-------+---------+---------------+

总分计算

对于数学，入门分数为 10，得分最高的学生人数为 2，因此 10/2 = 5 对于历史，入学分数是 20，学生的最高分是 3，所以 20/3 = 6.66

我试过的查询：

select student_id,marks,subject from
(
select student_id,marks,subject,dense_rank() over ( partition by subject order by marks desc) rn  from test
) t
where rn=1

输出：

+------------+-------+---------+ 
| Student_id | Marks | Subject | 
+------------+-------+---------+ 
|          1 |    50 | Maths   | 
|          2 |    50 | Maths   | 
|          1 |    30 | History | 
|          2 |    30 | History | 
|          3 |    30 | History | 
+------------+-------+---------+

我不知道如何在查询中获取总分列

Answer 1

我假设最高分是同一主题所有分数中的最高分。

SELECT 
    Student_ID
    ,Marks
    ,T.Subject
    ,CONVERT(decimal(18, 2), 
       CONVERT(float, EntryPoints)/
       CONVERT(float, COUNT(*) OVER(PARTITION BY T.Subject))) as 'TotalPoints'
  FROM @T T
  INNER JOIN (SELECT DISTINCT Subject, MAX(Marks) OVER(PARTITION BY Subject) 
  as Max_Marks FROM @T) Scores
  ON T.Subject = Scores.Subject

  WHERE Marks = Scores.Max_Marks
  ORDER BY Marks DESC, Student_ID

Answer 2

您可以在查询中使用 Group by 来获取主题的计数，然后 join 使用相同的查询获得结果。

下一个：-

Select a.student_id,a.marks,a.subject, 
Cast(a.EntryPoints as decimal ) / cast(b.CountPerSubject as decimal) TotalPoints   
from 
(
select student_id,marks,subject ,EntryPoints
    from
    (
            select student_id,marks,
            subject, EntryPoints,
            dense_rank() over ( partition by subject order by marks desc) rn  

            from test
    ) t
where rn=1
) a

Left Join
(
    select subject, count(subject) CountPerSubject
    from
    (
    select student_id,marks,subject ,EntryPoints
    from
    (
            select student_id,marks,
            subject, EntryPoints,
            dense_rank() over ( partition by subject order by marks desc) rn  

            from test
    ) t
where rn=1 ) c

group by subject) b
on a.subject =  b.subject

需要以用户数量为先来拆分入口点

Need to split entry points with the number of user comes first

sql-server

sql-server-2008

tsql

sql-server-2008-r2