一所美國大學(xué)有來自亞洲、歐洲和美洲的學(xué)生营罢，他們的地理信息存放在如下 `student` 表中戈稿。
| name | continent |
|--------|-----------|
| Jack | America |
| Pascal | Europe |
| Xi | Asia |
| Jane | America |
寫一個查詢語句實現(xiàn)對大洲（continent）列的 [透視表](https://zh.wikipedia.org/wiki/%E9%80%8F%E8%A7%86%E8%A1%A8) 操作穷缤，使得每個學(xué)生按照姓名的字母順序依次排列在對應(yīng)的大洲下面录淡。輸出的標題應(yīng)依次為美洲（America）扩劝、亞洲（Asia）和歐洲（Europe）江滨。數(shù)據(jù)保證來自美洲的學(xué)生不少于來自亞洲或者歐洲的學(xué)生铛纬。
對于樣例輸入，它的對應(yīng)輸出是：
| America | Asia | Europe |
|---------|------|--------|
| Jack | Xi | Pascal |
| Jane | | |
**進階：**如果不能確定哪個大洲的學(xué)生數(shù)最多唬滑，你可以寫出一個查詢?nèi)ド缮鲜鰧W(xué)生報告嗎告唆？
select
America,
Asia,
Europe
from
(select
@rownumber:=@rownumber+1 as id,
name as America
from
student,(select @rownumber:=0) a
where
continent = 'America'
order by
name) america
left join
(select
@rownumber2:=@rownumber2+1 as id,
name as Asia
from
student,(select @rownumber2:=0) a
where
continent = 'Asia'
order by
name) asia
on
america.id = asia.id
left join
(select
@rownumber3:=@rownumber3+1 as id,
name as Europe
from
student,(select @rownumber3:=0) a
where
continent = 'Europe'
order by
name) europe
on
america.id = europe.id
