PostgreSQL 选择 r.* by MIN() 并在两列上进行分组

Posted 2023-02-16

【中文标题】PostgreSQL 选择 r.* by MIN() 并在两列上进行分组

【英文标题】：PostgreSQL Select the r.* by MIN() with group-by on two columns

【发布时间】：2021-04-28 08:30:23

【问题描述】：

名为results 的表的示例架构

id	user_id	activity_id	activity_type_id	start_date_local	elapsed_time
1	100	11111	1	2014-01-07 04:34:38	4444
2	100	22222	1	2015-04-14 06:44:42	5555
3	100	33333	1	2015-04-14 06:44:42	7777
4	100	44444	2	2014-01-07 04:34:38	12345
5	200	55555	1	2015-12-22 16:32:56	5023

问题

通过activity_type_id和year选择每个用户最快活动的结果（即最小经过时间）。

（基本上，在这个简化的示例中，记录 ID=3 应该从选择中排除，因为记录 ID=2 对于给定 activity_type_id 1 和 2015 年的用户 100 是最快的）

我尝试过的

SELECT user_id,
       activity_type_id,
       EXTRACT(year FROM start_date_local) AS year,
       MIN(elapsed_time) AS fastest_time
FROM results
GROUP BY activity_type_id, user_id, year
ORDER BY activity_type_id, user_id, year;

实际

选择我想要的正确结果集，但只包含按列分组

user_id	activity_type_id	year	fastest_time
100	1	2014	4444
100	1	2015	5555
100	2	2014	12345
200	1	2015	5023

目标

拥有所有列的实际完整记录。即results.* + year

id	user_id	activity_id	activity_type_id	start_date_local	year	elapsed_time
1	100	11111	1	2014-01-07 04:34:38	2014	2014
2	100	22222	1	2015-04-14 06:44:42	2015	5555
4	100	44444	2	2014-01-07 04:34:38	2014	12345
5	200	55555	1	2015-12-22 16:32:56	2015	5023

【参考方案1】：

您可以为此使用窗口函数：

select id, user_id, activity_id, activity_type_id, start_date_local, year, elapsed_time
from (
  SELECT id, 
         user_id,
         activity_id,
         activity_type_id,
         start_date_local,
         EXTRACT(year FROM start_date_local) AS year,
         elapsed_time,
         min(elapsed_time) over (partition by user_id, activity_type_id, EXTRACT(year FROM start_date_local)) as fastest_time
  FROM results
) t
where elapsed_time = fastest_time
order by activity_type_id, user_id, year;

或者使用distinct on ()

select distinct on (activity_type_id, user_id, extract(year from start_date_local)) 
       id, 
       user_id,
       activity_id,
       activity_type_id,
       extract(year from start_date_local) as year,
       elapsed_time
from results
order by activity_type_id, user_id, year, elapsed_time;

Online example

【参考方案2】：

我想你想要这个：

SELECT DISTINCT ON (user_id, activity_type_id, EXTRACT(year FROM start_date_local)) 
     *, EXTRACT(year FROM start_date_local) AS year
FROM results
ORDER BY user_id, activity_type_id, year, elapsed_time;