SQL。 获得最大值（平均（列））

Question

我已经简化了我的问题并创建了这个例子来更好地说明。

我的桌子：

CREATE TABLE `table_company` (
  `source_id` INT(10) UNSIGNED NOT NULL,
  `company_id` INT(10) UNSIGNED NOT NULL,
  `clicks` INT(10) UNSIGNED NOT NULL,
  PRIMARY KEY (`source_id`,`company_id`)
) ENGINE=INNODB DEFAULT CHARSET=utf8;

我的数据：

INSERT INTO table_company VALUES
(1,100,8),(2,100,7),(3,200,9),(4,300,3),(5,100,4),(6,400,5),(7,100,10),(8,500,4),(9,500,9),(10,400,9);


SELECT source_id,company_id,AVG(clicks) AS avg_click FROM table_company
GROUP BY source_id,company_id
ORDER BY avg_click DESC;

给我：

source_id  company_id  avg_click  
---------  ----------  -----------
        7         100      10.0000
        3         200       9.0000
        9         500       9.0000
       10         400       9.0000
        1         100       8.0000
        2         100       7.0000
        6         400       5.0000
        5         100       4.0000
        8         500       4.0000
        4         300       3.0000

我想写一个查询给我：

source_id  company_id  avg_click  
---------  ----------  -----------
        7         100      10.0000
        3         200       9.0000
        9         500       9.0000
       10         400       9.0000
        4         300       3.0000

即。 只保留具有MAX的company_id（avg_click）

Answer 1

SELECT source_id, company_id, MAX(avg_click) as max_click FROM 
(SELECT source_id,company_id,AVG(clicks) AS avg_click FROM table_company
GROUP BY source_id,company_id
ORDER BY avg_click DESC) tmp
GROUP BY company_id

Answer 2

 SELECT MAx(source_id), company_id, MAX(avg_click)
 from (SELECT source_id,company_id,AVG(clicks) AS avg_click FROM #table_company 
    GROUP BY source_id,company_id 
    )as tbl
 GROUP by company_id 

Answer 3

您可以使用相关性：

SELECT source_id, company_id, avg_click
FROM table_company TC
WHERE avg_click=(SELECT max(avg_click)
             FROM table_company TC2
             WHERE TC.company_id=TC2.company_id
             GROUP BY TC2.company_id);

您还可以使用WITH子句：

WITH pom AS(SELECT company_id, max(avg_click) MaxAvgCl
            from table_company
            group by company_id)
SELECT pom.company_id, T.avg_click, T.source_id
FROM pom JOIN table_company T on T.company_id=pom.company_id 
                              and T.avg_click=pom.MaxAvgCl;