SQL 87 ) 最差是第几名(一)

用转置函数 case when 解决

select grade ,
case grade when 'A' then (select sum(number) from class_grade where grade <= 'A')
            when 'B' then (select sum(number)from class_grade where grade <= 'B')
            when 'C' then (select sum(number)from class_grade where grade <= 'C')
            when 'D' then (select sum(number)from class_grade where grade <= 'D')
            else (select sum(number) from class_grade)
    end
from class_grade
order by grade

用窗口函数sum()over()解决

select grade, sum(number)over(order by grade asc)t_rank
from class_grade
order by grade