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我对SQL真的很陌生，基本上已经用谷歌搜索了我的方式，我现在很卡住..所以我希望有人能提供帮助！

目标：为MS SQL Server中的每个trip_id获取每天具有最新时间戳的行（需要连接多个表以获取所需的数据）。

所以每个 trip_id 应该每天有 1 行，就像这样...... [删除了一些列以提高可读性]

timestamp,trip_id,stop_id,stop_code,arrival_time,departure_delay
4/28/2017 18:29,8888922,2847,52818,11:02:34,0
4/27/2017 18:26,8888922,2847,52818,11:02:34,60
4/25/2017 18:27,8888922,2847,52818,11:02:34,-120
4/28/2017 18:56,8888922,2847,52818,11:32:34,-60
4/25/2017 18:59,8888922,2847,52818,11:32:34,120
4/28/2017 19:34,8888922,2847,52818,12:02:34,360
4/27/2017 19:31,8888922,2847,52818,12:02:34,540
4/25/2017 19:27,8888922,2847,52818,12:02:34,-120

但是现在我能做的最好的事情是使用以下查询获取每天的最大时间戳和离开延迟

select
max(trip_updates.timestamp) as max, stop_times.trip_id, stops.stop_id, stops.stop_code, stop_times.arrival_time, trips.service_id,
stops.stop_name, stop_times.shape_dist_traveled, stop_time_updates.departure_delay
from stops
inner join stop_times on stops.stop_id = stop_times.stop_id
inner join trips on trips.trip_id = stop_times.trip_id
inner join routes on trips.route_id = routes.route_id
inner join trip_updates on stop_times.trip_id = trip_updates.trip_id
inner join stop_time_updates on trip_updates.oid = stop_time_updates.trip_update_id
where
stop_code = '52818'
and service_id = '1'
and stop_times.arrival_time between '11:00%' and '14:00%'
and route_short_name = '134'
group by stop_times.trip_id, stops.stop_id, stops.stop_code, stop_times.arrival_time, trips.service_id,
stops.stop_name, stop_times.shape_dist_traveled, stop_time_updates.departure_delay
order by stop_times.arrival_time asc, max(trip_updates.timestamp) desc

这给了我这样的结果......

timestamp,trip_id,stop_id,stop_code,arrival_time,departure_delay
4/28/2017 18:29,8888922,2847,52818,11:02:34,0
4/28/2017 18:21,8888922,2847,52818,11:02:34,30
4/28/2017 18:16,8888922,2847,52818,11:02:34,60
4/28/2017 18:11,8888922,2847,52818,11:02:34,120
4/27/2017 18:26,8888922,2847,52818,11:02:34,60
4/27/2017 18:22,8888922,2847,52818,11:02:34,30
4/27/2017 18:20,8888922,2847,52818,11:02:34,0

感谢所有帮助！谢谢！

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2 回答 2

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您可以加入具有所需内容的子查询：

SELECT  last_trip.timestamp AS max ,
        stop_times.trip_id ,
        stops.stop_id ,
        stops.stop_code ,
        stop_times.arrival_time ,
        trips.service_id ,
        stops.stop_name ,
        stop_times.shape_dist_traveled ,
        stop_time_updates.departure_delay
FROM    stops
        INNER JOIN stop_times ON stops.stop_id = stop_times.stop_id
        INNER JOIN trips ON trips.trip_id = stop_times.trip_id
        INNER JOIN routes ON trips.route_id = routes.route_id

        -- instead of joining directly to trip_updates, join to query
        -- that will number the entries per day
        INNER JOIN ( SELECT * ,
                            ROW_NUMBER() OVER ( PARTITION BY trip_id ORDER BY timestamp DESC ) AS rownum
                     FROM   trip_updates
                   ) AS last_trip ON stop_times.trip_id = last_trip.trip_id and rownum = 1 -- and join on the latest

        INNER JOIN stop_time_updates ON trip_updates.oid = stop_time_updates.trip_update_id
WHERE   stop_code = '52818'
        AND service_id = '1'
        AND stop_times.arrival_time BETWEEN '11:00%'
                                    AND     '14:00%'
        AND route_short_name = '134'
GROUP BY stop_times.trip_id ,
        stops.stop_id ,
        stops.stop_code ,
        stop_times.arrival_time ,
        trips.service_id ,
        stops.stop_name ,
        stop_times.shape_dist_traveled ,
        stop_time_updates.departure_delay
ORDER BY stop_times.arrival_time ASC ,
        MAX(trip_updates.timestamp) DESC;
于 2017-05-02T00:27:56.760 回答
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正如我在评论中提到的，如果您需要选择所有当前列，实现此目的的一种方法是使用ROW_NUMBER()窗口函数并删除您的GROUP BY. 例如，

SELECT [Max] = [timestamp], trip_id, stop_id, stop_code, arrival_time, service_id, stop_name, shape_dist_traveled, departure_delay
FROM
(
    SELECT trip_updates.[timestamp], stop_times.trip_id, stops.stop_id, stops.stop_code, stop_times.arrival_time, 
           trips.service_id, stops.stop_name, stop_times.shape_dist_traveled, stop_time_updates.departure_delay,
           RN = ROW_NUMBER() OVER (PARTITION BY stop_times.trip_id, CAST(trip_updates.[timestamp] AS DATE) ORDER BY trip_updates.[timestamp] DESC) 
           -- This assigns a row number for each row within each trip_id and each day, where a row number of 1 will be the highest timestamp.
    FROM ... 

    <put all your current joins / where clauses here>

    AND route_short_name = '134'
    -- Note: no GROUP BY
) AS T
WHERE RN = 1 -- This ensures you select only the the first row for each trip_id.
ORDER BY arrival_time, [timestamp];
于 2017-05-02T00:25:12.553 回答