Question

我遇到的问题是每组只获得TOP 2值（组在列中）。

示例：

ID    Group    Value
1        A       30
2        A      150
3        A       40
4        A       70
5        B        0
6        B      100
7        B       90

我希望我的输出是

ID    Group    Value
 1       A       150
 2       A        70
 3       B       100
 4       B        90

简单地说，对于每个组，我只想要2行具有最高值

Answer 1

大多数数据库都支持ANSI标准row_number()功能。您可以将其用作：

select group, value
from (select t.*,
             row_number() over (partition by group order by value desc) as seqnum
      from t
     ) t
where seqnum <= 2;

要设置id，您可以在外部查询中使用row_number()：

select row_number() over (order by group, value) as id,
       group, value
from (select t.*,
             row_number() over (partition by group order by value desc) as seqnum
      from t
     ) t
where seqnum <= 2;

但是，更改id似乎很可疑。

Answer 2

您可以将CTE与排名函数ROW_NUMBER()一起使用。

以下是获取结果的查询。

;WITH cte AS
  ( SELECT Group, value,
           ROW_NUMBER() OVER (PARTITION BY Group ORDER BY value DESC) AS rn
    FROM test
  )
SELECT Group, value FROM cte
WHERE rn <= 2
ORDER BY value

为每个组选择TOP 2值

2 个答案: