如何获取表 A 中列的最小/最大值和 B 中的值，其中 B 的行由 A 中的另一列确定？

Question

我试图了解如何编写我的查询，以便对于某些列，它返回其他列具有最小值或最大值的值，同时返回这些列的最小值/最大值。

我有两个包含驱动器（开车旅行）和街道地址的 Postgresql 表，我想从中选择数据以将驱动器组合成旅行。例如，从我家到商店是一个驱动器，再回去是另一个驱动器，将两者组合在一起形成一个单程。对于每个这样的分组旅行，我想获取第一个驱动器的开始时间和地址，最终驱动器的结束时间和位置，以及所有驱动器时间和距离的总和。

这是获取我想组合成一次行程的三个驱动器的示例查询：

SELECT
    start_time,
    end_time,
    duration,
    distance,
    start_address.name AS start_address,
    end_address.name AS end_address
FROM drives
    LEFT JOIN addresses start_address ON start_address_id = start_address.id
    LEFT JOIN addresses end_address ON end_address_id = end_address.id
WHERE drives.id=ANY('{10, 11, 12}');

运行此查询可能会产生以下结果：

row# | start_time | end_time   | duration | distance | start_address | end_address
----------------------------------------------------------------------------------
1      14:40:00     14:43:00     3          0.75       Home            The store
2      14:48:00     14:58:00     10         2.25       The store       Post office
3      15:10:00     15:08:00     8          2.00       Post office     Work

现在，我想构建一个查询，该查询应该产生一行代表这三个驱动器的组合行程。我希望该行包含最小开始时间、最大结束时间、持续时间的总和、距离的总和、具有最小开始时间的行的起始地址和具有最长结束时间。

如果我省略地址部分，那很简单：

SELECT
    min(start_time) AS start_time,
    max(end_time) AS end_time,
    sum(duration) AS duration,
    sum(distance) AS distance
FROM drives
WHERE drives.id=ANY('{10, 11, 12}');

row# | start_time | end_time   | duration | distance
----------------------------------------------------
1      14:40:00     15:08:00     21          5.00

但是我如何编写查询以便我也得到地址？我想要这个结果：

row# | start_time | end_time   | duration | distance | start_address | end_address
----------------------------------------------------------------------------------
1      14:40:00     15:08:00     21          5.00      Home            Work

显然我需要将地址部分返回到查询中，但无论我尝试什么，我都无法弄清楚如何正确构造它。坦率地说，我什至不确定我得到了这个问题的标题：/

Answer 1

我们可以在主查询中使用窗口函数first_value和last_value，然后与一级子查询聚合为，

SELECT
    min(start_time) AS start_time,
    max(end_time) AS end_time,
    sum(duration) AS duration,
    sum(distance) AS distance,
    max(start_address) start_address,
    max(end_address) end_address  
FROM
(
    SELECT
        start_time,
        end_time,
        duration,
        distance,
        first_value(start_address.name) over (order by start_time,end_time) start_address,
        last_value(end_address.name) over (order by start_time,end_time rows between unbounded preceding and unbounded following) end_address
    FROM drives
        LEFT JOIN addresses start_address ON start_address_id = start_address.id
        LEFT JOIN addresses end_address ON end_address_id = end_address.id
    WHERE drives.id=ANY('{10, 11, 12}')
) c;