with sheet as 
(select name,marks,
    case 
        when marks between 0 and 9 then 1
        when marks between 10 and 19 then 2
        when marks between 20 and 29 then 3
        when marks between 30 and 39 then 4
        when marks between 40 and 49 then 5
        when marks between 50 and 59 then 6
        when marks between 60 and 69 then 7
        when marks between 70 and 79 then 8
        when marks between 80 and 89 then 9
        when marks between 90 and 100 then 10
    end as grade
  from students) 

select 
    case when sheet.grade<8 then NULL else sheet.name end as NAME,
    sheet.grade as GRADE,
    sheet.marks as MARKS
from sheet
order by GRADE desc,
 case when GRADE>=8 then NAME else null
      END ASC, 
 case when GRADE<8 then MARKS else null
      END desc;