如何在 SQL 服务器中为每个组/类别获取所需的行数

Question

我有这个查询用于从 SQL 服务器 table 检索行：

SELECT
    aid, 
    research_area_category_id, 
    CAST(research_area as VARCHAR(100)) [research_area], 
    COUNT(*) [Paper_Count]
FROM
    sub_aminer_paper 
GROUP BY
    aid, 
    research_area_category_id,
    CAST(research_area as VARCHAR(100))
HAVING 
    aid IN (SELECT
                aid
            FROM 
                sub_aminer_paper
            GROUP BY 
                aid
            HAVING 
                MIN(p_year) = 1990 AND MAX(p_year) = 2014 AND COUNT(pid) BETWEEN 10 AND 40
            )
ORDER BY aid ASC, Paper_Count DESC

哪个 returns 这个输出：

aid     research_area_category_id   research_area                Paper_Count  
2937    33                          markov chain                 3  
2937    33                          markov decision process      1  
2937    1                           optimization problem         1  
2937    27                          real time application        1  
2937    32                          software product lines       1  
11120   29                          aspect oriented programming  4  
11120   1                           graph cut                    2  
11120   1                           optimization problem         2  
11120   32                          uml class diagrams           1  
11120   25                          chinese word segmentation    1   
11120   29                          dynamic programming          1  
11120   19                          face recognition             1  
11120   1                           approximation algorithm      1  
12403   2                           differential equation        7  
12403   1                           data structure               2  
12403   34                          design analysis              1  
12403   9                           object detection             1  
12403   27                          operating system             1  
12403   1                           problem solving              1  
12403   21                          archiving system             1  
12403   2                           calculus                     1

现在返回的输出包括与各自 aid 相关的所有行，而我只需要每个 aid ORDER BY Paper_Count DESC 的前 3 行，即包含的行Paper_Count 3, 1, 1 的值 aid 2937，4,2,2 的 11120 和 7,2,2 的 12403。

请帮忙！谢谢。

Answer 1

一种方法是在您的结果集上应用 row_number() over(partition by aid order by Paper_Count desc) as rn，然后 select 所有具有 rn<=3

的记录

with cte
as
(
SELECT
    aid, 
    research_area_category_id, 
    CAST(research_area as VARCHAR(100)) [research_area], 
    COUNT(*) [Paper_Count]
FROM
    sub_aminer_paper 
GROUP BY
    aid, 
    research_area_category_id,
    CAST(research_area as VARCHAR(100))
HAVING 
    aid IN (SELECT
                aid
            FROM 
                sub_aminer_paper
            GROUP BY 
                aid
            HAVING 
                MIN(p_year) = 1990 AND MAX(p_year) = 2014 AND COUNT(pid) BETWEEN 10 AND 40
            )
ORDER BY aid ASC, Paper_Count DESC
)
,
cte1
AS
( 
   SELECT * ,
   ROW_NUMBER() OVER (PARTITION BY aid ORDER BY Paper_Count DESC) AS rn 
   FROM cte 
)

SELECT * FROM cte1 WHERE rn<=3

如何在 SQL 服务器中为每个组/类别获取所需的行数

How to get desired number of rows for each group / category in SQL Server

sql-server

rows

row-number