select America, Asia, Europe
from
(select name as America,row_number() over (order by name ASC) as rn from student where continent='America') a
left join
(select name as Asia,row_number() over (order by name ASC) as rn from student where continent='Asia') b
on a.rn=b.rn
left join
(select name as Europe,row_number() over (order by name ASC) as rn from student where continent='Europe') c
on c.rn=a.rn