PostgreSQL Select r.* by MIN() 在两列上进行分组

Question

名为 results

的 table 的示例模式

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

Select activity_type_id 和 year.

每个用户的最快活动（即最短运行时间）的结果

（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 来说是最快的）

我试过的

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

其中选择了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

拥有包含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

Answer 1

您可以为此使用 window 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

Answer 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;