Question

我有这样的场景，

 Studentid|Subject1|Subject2|Subject3|Subject4|Subject5|Grade

   1      |   1    |    1   |   1    |   1    |    1   |
   2      |   1    |    2   |   2    |   2    |    3   |
   .....etc

该表显示了学生ID及其在每个项目中的排名。我想根据以下条件更新成绩栏，

1）如果所有科目排名均为1，则毕业生应为A 2）如果任何3个等级是1，而其他2个主体等级为2，那么B 3）如果任何3个等级是2，而其他2个主体等级为3，那么c

等等......像这样可以有很多条件。所以我只想知道解决方法。

是否可以编写单个查询？

Answer 1

您可以移动表格来计算成绩：

;with 
Subject1 as (
  select Studentid, 1 as SubjectCode, Subject1 as subjectResult
  from your_table
),
Subject2 as (
  select Studentid, 2 as SubjectCode, Subject2 as subjectResult
  from your_table
),
...
Subject5 as (
  select Studentid, 5 as SubjectCode, Subject5 as subjectResult
  from your_table
),
subjects as (
   select * from Subject1 union all
   select * from Subject2 union all
   ...
   select * from Subject5

) 
select 
   Studentid, sum( subjectResult )
from
   subjects
group by
   Studentid

请注意，在最后一次选择中，您可以使用case语句计算成绩。您也可以稍加升级Grade列升级：

...),
subjects as (
   select * from Subject1 union all
   select * from Subject2 union all
   ...
   select * from Subject5

), 
grades as (
 select 
   Studentid, sum( subjectResult ) as grade
 from
   subjects
 group by
   Studentid
)
update t set grade = grades.grade
from your_table t 
inner join grades on t.Studentid = grades.Studentid

Answer 2

同意所有其他评论，这是一种存储数据的糟糕方式。但如果你陷入困境并且必须使用它，那么这样的事情可能有效：

UPDATE StudentsTable
SET StudentsTable.Grade = CASE 
    WHEN Tally.Total < 8
        THEN 'A'
    WHEN Tally.Total < 13
        THEN 'B'
    ELSE 'C'
    END
FROM StudentsTable AS St
JOIN (
    SELECT StudentID,
    Subject1 + Subject2 + Subject3 + Subject4 + Subject5 AS [Total]
FROM StudentsTable
) AS Tally
    ON St.StudentID = Tally.StudentID

根据需要修改CASE语句。它不漂亮，但它应该做的伎俩。

Answer 3

我使用了UNPIVOT：

CREATE TABLE s
    (
      Studentid INT ,
      Subject1 INT ,
      Subject2 INT ,
      Subject3 INT ,
      Subject4 INT ,
      Subject5 INT ,
      Grade CHAR(1)
    )

INSERT INTO [s] VALUES 
(   1      ,   1    ,    1   ,   1    ,   1    ,    1   , ''),
(   2      ,   1    ,    2   ,   2    ,   2    ,    3   , '')

WITH cte AS (
SELECT u.StudentID, AVG(u.[g]) AS [grade]
from (SELECT * FROM [s]) AS [f]
UNPIVOT (g FOR [SUBJECT] IN (Subject1, Subject2, Subject3, Subject4, Subject5)) AS [u]
GROUP BY u.StudentID
)
UPDATE [s]
SET [Grade] = CASE
    WHEN c.[grade] <=1 THEN 'A'
    WHEN c.[grade] <=2 THEN 'B'
    WHEN c.[grade] <=3 THEN 'C'
    WHEN c.[grade] <=4 THEN 'D'
    ELSE 'F'
END
FROM [cte] AS [c]
INNER JOIN [dbo].[s]
    ON [c].StudentId = [s].[Studentid]

正如其他人所说，你的评分指标有点含糊不清，但我猜了一下。如果它不同，请根据需要进行更改。

如何用tsql计算学生的成绩？

3 个答案: