在每个类别的SQL中选择排名前2位的销售额

Question

我有只想在每个班级中选择前2个销售额的表，结果是

Sophia   A 40
Jennifer A 15
Greg     B 50
Jeff     B 20
Stella   B 20 

Answer 1

您可以使用RANK：

SELECT *
FROM (SELECT *, RANK() OVER(PARTITION BY class ORDER BY sales DESC) AS rnk
      FROM tab) sub
WHERE rnk <=2;

Answer 2

窗口函数density_rank也满足样本数据的预期结果条件

 select * from
    (select * , dense_rank() over(partition by class order by scores DESC ) as rn 
     from tablea
     ) t where rn<=2