SQL case

select case when gd<8 then 'NULL' else name
            end as nm,gd,marks from (
select id,name,marks,
case when marks >=0 and marks <=9 then 1
    when marks >=10 and marks <=19 then 2
    when marks >=20 and marks <=29 then 3
    when marks >=30 and marks <=39 then 4
    when marks >=40 and marks <=49 then 5
    when marks >=50 and marks <=59 then 6
     when marks >=60 and marks <=69 then 7
     when marks >=70 and marks <=79 then 8
     when marks >=80 and marks <=89 then 9
     when marks >=90 and marks <=100 then 10
     else 0 end as gd
from students
    )
order by gd desc,name
;