有这么个表
fans(team,nationality,fanCount)
'Barcelona','Germany',12000
'Barcelona','Spain',18000
'Barcelona','China',13000
'Barcelona','USA',15000
'Barcelona','Italy',11000
'Real Madrid','France',19000
'Real Madrid','Germany',13000
'Real Madrid','USA',17000
'Real Madrid','Korea',16000
'Real Madrid','UK',12000
现在分别要求出每个team粉丝数最多的3个国家
select * from fans t1 where ( select count(*) from fans t2 where t1.team=t2.team and t2.fanCount>=t1.fanCount ) <=3