也许，这就是你要找的。

select * from (
select rank() over (partition by region,device order by cn desc) as
top_num,player_id, region,device,cn from 
(
select count(*) as cn , player_id,region,device from 
test_table group by player_id,region,device 
)l
)t 
where top_num = 1;

如果这有帮助，请告诉我。
op edit：我使用您提供的查询成功地实现了我想要的功能；这是最后一个

WITH combo 
 AS (SELECT user_id, 
            region, 
            device 
     FROM   (SELECT Rank() 
                      OVER ( 
                        partition BY region, device 
                        ORDER BY cn DESC) AS top_num, 
                    user_id, 
                    region, 
                    device, 
                    cn 
             FROM   (SELECT Count(*) AS cn, 
                            user_id, 
                            region, 
                            device 
                     FROM   samples 
                     GROUP  BY user_id, 
                               region, 
                               device)l)t 
     WHERE  top_num = 1) 
SELECT s.user_id, 
   s.region, 
   s.device 
FROM   samples s 
   JOIN combo 
     ON s.user_id = combo.user_id 
        AND s.region = combo.region 
        AND s.device = combo.device