题解 | #最差是第几名(一)#

select 
a.grade, 
sum(a.number)over(order by a.grade)
from class_grade a
order by 1
或
select
grade,
case when grade='A' then (select sum(t.number) from class_grade t where t.grade='A')
     when grade='B' then (select sum(t1.number) from class_grade t1 where t1.grade<='B')
     when grade='C' then (select sum(t2.number) from class_grade t2 where t2.grade<='C')
     when grade='D' then (select sum(t3.number) from class_grade t3 where t3.grade<='D') 
     else (select sum(t4.number) from class_grade t4) end
from class_grade
order by 1