根据使用SQL /等级/ DENSE_RANK（）表字母排序

Question

我有不同的等级，并使用他们排名相应调整至其刻度：

select id,subject,semester,student,course,mark,grade 
,dense_rank() over(PARTITION by course order by mark desc) as RANK 
from courses c 
LEFT JOIN course_enrolments b ON c.id=b.course; 

，其结果是：

id subject semester student course mark grade rank 
5270 1001 126 1077055 5270 99  HD 1 
5270 1001 126 1076079 5270 98  HD 2 
5270 1001 126 1077334 5270 85  HD 3 
5270 1001 126 1076920 5270 84  DN 4 
5270 1001 126 1077443 5270 84  DN 5 
5270 1001 126 1072135 5270 67  CR 6 
5270 1001 126 1079997 5270 66  CR 7 
5270 1001 126 1071034 5270 62  PS 8 
5270 1001 126 1079993 5270 62  PS 9 
5270 1001 126 1074070 5270 44  FL 10 
5270 1001 126 1078409 5270 30  FL 11 
5270 1001 126 1073006 5270 28  FL 12 

但是我试图做到的是排列这些人根据自己的成绩和没有按照他们的标志：

所以我试图做到的，是这样的：

id subject semester student course mark grade rank 
5270 1001 126 1077055 5270 99  HD 1 
5270 1001 126 1076079 5270 98  HD 1 
5270 1001 126 1077334 5270 85  HD 1 
5270 1001 126 1076920 5270 84  DN 2 
5270 1001 126 1077443 5270 84  DN 2 
5270 1001 126 1072135 5270 67  CR 3 
5270 1001 126 1079997 5270 66  CR 3 
5270 1001 126 1071034 5270 62  PS 4 
5270 1001 126 1079993 5270 62  PS 4 
5270 1001 126 1074070 5270 44  FL 5 
5270 1001 126 1078409 5270 30  FL 5 
5270 1001 126 1073006 5270 28  FL 5 

我怎样才能做到这一点？ 谢谢，

Answer 1

如果有帮助，我会在SQL Server中使用以下内容。也许你（或某人）可以翻译它？

DECLARE @GradeRankTVP Table (
    Grade Varchar(2), 
    GradeRank int 
); 
INSERT INTO @GradeRankTVP (Grade, GradeRank) VALUES 
    (HD, 1) 
    ,(DN, 2) 
    ,(CR, 3) 
    ,(PS, 4) 
    ,(FL, 5) 
-- ,etc 
; 
select c.id, c.subject, c.semester, b.student, c.course, b.mark, b.grade 
, d.GradeRank 
from courses c 
LEFT JOIN course_enrolments b ON c.id = b.course 
LEFT JOIN @GradeRankTVP AS d on b.grade = d.Grade 

Answer 2

你应该能够做到这一点，其在Oracle和SQL Server的工作原理：

select id,subject,semester,student,course,mark,grade, 
case when grade = 'HD' then 1 
    when grade = 'DN' then 2 
    when grade = 'CR' then 3 
    when grade = 'PS' then 4 
    when grade = 'FL' then 5 
end as RANK 
from courses c 
order by mark desc