如何为查询 mysql 添加临时值

Question

我的数据库中有以下查询，我想添加一个新列来处理学生的最终感谢：查询：

select student_name,q4.percentage
  from (select q2.student_id,mark *100/total as Percentage
          from (select class_id,sum(max_mark)as total
                  from course
                 group by(class_id)
               )q1 ,
               (select sum(mark) as mark,student_id
                  from grades
                 group by(student_id)
               ) q2
         where q2.student_id in (select student_id
                                   from student
                                  where student.section_id in(select section_id 
                                                                from section 
                                                               where class_id=q1.class_id)
                                )
         order by q2.student_id
       ) q4
inner join student on q4.student_id=student.student_id;

结果如下： enter image description here

STUDENT_NAME	PERCENTAGE
Massoud	50.41667
Ali-Shbeeb	84.16667
Mona	75.2941

现在我只需要在结果中添加一个新列，比如奖励所以 table 就像：

student_name     percetage award 
mahmoud-kabbani  79.166667 B
Kareem-Alshaeer  54.583    c

Answer 1

您可以包含 1 列 case 语句，如下所示 -

select student_name,q4.percentage,
       CASE WHEN q4.percentage > 80 THEN 'A'
            WHEN q4.percentage > 60 THEN 'B'
            WHEN q4.percentage > 40 THEN 'C'
            ELSE 'E'
       END award
  from (select q2.student_id,mark *100/total as Percentage
          from (select class_id,sum(max_mark)as total
                  from course
                 group by(class_id)
               )q1 ,
               (select sum(mark) as mark,student_id
                  from grades
                 group by(student_id)
               ) q2
         where q2.student_id in (select student_id
                                   from student
                                  where student.section_id in(select section_id 
                                                                from section 
                                                               where class_id=q1.class_id)
                                )
         order by q2.student_id
       ) q4
inner join student on q4.student_id=student.student_id;

如何为查询 mysql 添加临时值

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