mysql 表格处理-每个同一组别取出最大前3笔数据

Question

如题，如何用mysql语法写出右图的效果

以组别为区分，分别区出金额前3名的资料

Answer 1

select *
from (
select a.组别,a.省份,a.金额,count(*) ct
from table a 
left join table b 
on a.组别=b.组别
where a.金额<=b.金额
group by a.组别,a.省份,a.金额
) t 
where ct<=3