Sql 基于日期时间列中的间隔时间阈值修改行的id值

我正在研究geolife，它在一个文本文件.plt中包含用户的时间戳GPS跟踪。每个文本文件包含用户一次行程的GPS点。因此，我使用python脚本将数据集导入postgres

由于文件是根据行程的开始时间用数字字符串命名的，因此，例如，下表中包含行程的文件是20070920074804.plt，因此我为行程id会话_id提供了文件名，但不带扩展名。这是这张桌子上的原始GPS轨迹

出于分析目的，我创建了另一个表trips_metrics，其中我从轨迹表计算trip metrics，并将结果插入trip_metrics。我计算的值包括行程距离haversine和持续时间开始时间-结束时间

然后我注意到一些奇怪的事情，一个用户进行了8小时的行程，但行程为321米。彻底浏览行程文件时，我注意到行程时间有跳跃，建议在行程中休息，用户可能停留数小时，然后继续。上表第3行和第4行中有一个示例

为了获得准确的行程时间，我需要对这些情况下的行程进行拆分，如果连续行之间的时间间隔超过30分钟，则应将其视为新的行程，从而获得新的ID

我打算加上数字…02，…03。。在实际计算trips指标（即修改轨迹表）之前，在“我的轨迹表”中输入行程的当前会话id。 因此，对于上表中的示例，我想按如下方式进行拆分：

 user_id |    session_id     |       timestamp        |    lat    |    lon     | alt 
---------+-------------------+------------------------+-----------+------------+-----
      11 |  20070920074804   | 2007-09-20 07:48:04+01 |  28.19737 | 113.006795 |  71
      11 |  20070920074804   | 2007-09-20 08:07:09+01 | 28.197685 | 113.006792 |  87
      11 |  20070920074804   | 2007-09-20 08:07:10+01 | 28.197685 |  113.00679 |  87
      11 |  2007092007480402 | 2007-09-20 14:03:50+01 | 28.197342 | 113.007422 |  62
      11 |  2007092007480402 | 2007-09-20 14:04:59+01 | 28.197108 |  113.00734 |  62
      11 |  2007092007480402 | 2007-09-20 14:05:01+01 | 28.197088 |  113.00727 |  62

请注意我是如何为新行程分配session_id的，因为两者之间的时间超过30分钟

我如何在postgres中修改或更改我的原始GPS表轨迹

编辑

答：@GMB答案中的第一个查询是有效的，但是，它在new_session_id列中为每一行提供了一个新的session_id

预期结果：

我们的想法是通过旧的会话id+01为新兴的旅行提供一个新的id。如果遇到另一个新的行程，则应为其分配旧的会话id+02，以此类推

B:第二个带更新选项的查询包含语法错误：

update trajectories t
from (
    select 
        t.*,
        case when sum(is_gap) over(partition by session_id order by timestamp) > 0
            then session_id * 100 + sum(is_gap) over(partition by session_id order by timestamp)
            else session_id
        end new_session_id
    from (
        select
            t.*,
            (timestamp > lag(timestamp) over(partition by session_id order by timestamp))::int is_gap
        from trajectories t
    ) t
) t1
set session_id = t1.new_session_id
where t1.session_id = t.session_id and t1.timestamp = t.timestamp

ERROR:  syntax error at or near "from"
LINE 2: from (

您可以使用lag（一个累计总和）来标识分段，然后使用某种方式来调整会话id：

---

这是一个空白和孤岛问题。您希望检测时间戳差异大于30分钟的连续行，然后相应地更改会话id

一个选项是使用lag，然后是间隙的累积计数-然后可以使用该信息计算新的会话id：

如果需要，可以将其转换为update语句：

update trajectories t
set session_id = t1.new_session_id
from (
    select 
        t.*,
        case when sum(is_gap) over(partition by session_id order by timestamp) > 0
            then session_id * 100 + sum(is_gap) over(partition by session_id order by timestamp)
            else session_id
        end new_session_id
    from (
        select
            t.*,
            (timestamp > lag(timestamp) over(partition by session_id order by timestamp))::int is_gap
        from trajectories t
    ) t
) t1
where t1.session_id = t.session_id and t1.timestamp = t.timestamp

---

谢谢你的回答。我真的很想用update选项来回答这个问题，但是它需要像我的问题编辑中所说的那样重新阅读。@someone:my bad，Postgres希望set子句在from子句之前。已修复。获取SQL语法错误：错误：关系t不存在第9行：从t@someone . . . 这是您的表名。在这个db提琴中，我说明了错误。看来这个答案考虑了过滤要求，30分钟间隔我不明白为什么postgres总是抱怨子查询别名。你能看看我上面评论中的db提琴吗？@someone。哎呀，那应该是一个窗口函数。我修复了查询并添加了一个dbfiddle。

+---------+----------------+------------------------+-----------+------------+-----+--------+------------------+
| user_id |   session_id   |       timestamp        |    lat    |    lon     | alt | is_gap |  new_session_id  |
+---------+----------------+------------------------+-----------+------------+-----+--------+------------------+
|      11 | 20070920074804 | 2007-09-20 07:48:04+01 | 28.19737  | 113.006795 |  71 |        |   20070920074804 |
|      11 | 20070920074804 | 2007-09-20 08:07:09+01 | 28.197685 | 113.006792 |  87 |        |   20070920074804 |
|      11 | 20070920074804 | 2007-09-20 08:07:10+01 | 28.197685 | 113.00679  |  87 |      1 | 2007092007480401 |
|      11 | 20070920074804 | 2007-09-20 14:03:50+01 | 28.197342 | 113.007422 |  62 |      1 | 2007092007480401 |
|      11 | 20070920074804 | 2007-09-20 14:04:59+01 | 28.197108 | 113.00734  |  62 |      1 | 2007092007480401 |
|      11 | 20070920074804 | 2007-09-20 14:05:01+01 | 28.197088 | 113.00727  |  62 |      1 | 2007092007480401 |
+---------+----------------+------------------------+-----------+------------+-----+--------+------------------+

update trajectories t
from (
    select 
        t.*,
        case when sum(is_gap) over(partition by session_id order by timestamp) > 0
            then session_id * 100 + sum(is_gap) over(partition by session_id order by timestamp)
            else session_id
        end new_session_id
    from (
        select
            t.*,
            (timestamp > lag(timestamp) over(partition by session_id order by timestamp))::int is_gap
        from trajectories t
    ) t
) t1
set session_id = t1.new_session_id
where t1.session_id = t.session_id and t1.timestamp = t.timestamp

ERROR:  syntax error at or near "from"
LINE 2: from (

select (case when grp >= 1 then session_id * 100 + grp
             else session_id
        end) as new_session_id,
       t.*
from (select t.*,
             count(*) filter (where prev_ts < timestamp - interval '30 minute') over (partition by session_id, order by timestamp) as grp
      from (select t.*, 
                   lag(timestamp) over (partition by session_id order by timestamp) as prev_ts
            from trajectories t
           ) t
     ) t;

select 
    t.*,
    case when sum(is_gap) over(partition by session_id order by timestamp) > 0
        then session_id * 100 + sum(is_gap) over(partition by session_id order by timestamp)
        else session_id
    end new_session_id
from (
    select
        t.*,
        (timestamp > lag(timestamp) over(partition by session_id order by timestamp))::int is_gap
    from trajectories t
) t

update trajectories t
set session_id = t1.new_session_id
from (
    select 
        t.*,
        case when sum(is_gap) over(partition by session_id order by timestamp) > 0
            then session_id * 100 + sum(is_gap) over(partition by session_id order by timestamp)
            else session_id
        end new_session_id
    from (
        select
            t.*,
            (timestamp > lag(timestamp) over(partition by session_id order by timestamp))::int is_gap
        from trajectories t
    ) t
) t1
where t1.session_id = t.session_id and t1.timestamp = t.timestamp