Postgresql查询每组的前N条记录

Postgresql以指定字段分组后，查询每组的前N条记录

 主函数：

ROW_NUMBER() OVER (PARTITION BY "省份名称","地市名称"  ORDER BY arpu desc ,dou DESC) AS row_id

在原有数据表的基础上以  "省份名称","地市名称" 分组，按"arpu desc ,dou DESC"排序后，生成一个新字段row_id。然后再以row_id为筛选条件查询数据。<=3：只取前3天数据

select * from (
    select *,ROW_NUMBER() OVER (PARTITION BY "省份名称","地市名称"  ORDER BY arpu desc ,dou  DESC) AS row_id
FROM "全国表" t
     WHERe "省份名称" = '河南'
        and "地市名称" = '开封'
) t
    where  t.row_id <=3