4

无论如何都要计算彼此接近但不一定在固定时间范围内的给定时间戳运行？

即，不是按小时或分钟分组，而是按当前行的时间戳与下一行的时间戳的接近程度分组。如果下一行在“x”秒/分钟内，则将该行添加到组中，否则开始新的分组。

鉴于此数据：

+----+---------+---------------------+
| id | item_id | event_date          |
+----+---------+---------------------+
|  1 |       1 | 2013-05-17 11:59:59 |
|  2 |       1 | 2013-05-17 12:00:00 |
|  3 |       1 | 2013-05-17 12:00:02 |
|  4 |       1 | 2013-05-17 12:00:03 |
|  5 |       3 | 2013-05-17 14:05:00 |
|  6 |       3 | 2013-05-17 14:05:01 |
|  7 |       3 | 2013-05-17 15:30:00 |
|  8 |       3 | 2013-05-17 15:30:01 |
|  9 |       3 | 2013-05-17 15:30:02 |
| 10 |       1 | 2013-05-18 09:12:00 |
| 11 |       1 | 2013-05-18 09:13:30 |
| 12 |       1 | 2013-05-18 09:13:45 |
| 13 |       1 | 2013-05-18 09:14:00 |
| 14 |       2 | 2013-05-20 15:45:00 |
| 15 |       2 | 2013-05-20 15:45:03 |
| 16 |       2 | 2013-05-20 15:45:10 |
| 17 |       2 | 2013-05-23 07:36:00 |
| 18 |       2 | 2013-05-23 07:36:10 |
| 19 |       2 | 2013-05-23 07:36:12 |
| 20 |       2 | 2013-05-23 07:36:15 |
| 21 |       1 | 2013-05-24 11:55:00 |
| 22 |       1 | 2013-05-24 11:55:02 |
+----+---------+---------------------+

期望的结果：

+---------+-------+---------------------+
| item_id | total | last_date_in_group  |
+---------+-------+---------------------+
|       1 |     4 | 2013-05-17 12:00:03 |
|       3 |     2 | 2013-05-17 14:05:01 |
|       3 |     3 | 2013-05-17 15:30:02 |
|       1 |     4 | 2013-05-18 09:14:00 |
|       2 |     3 | 2013-05-20 15:45:10 |
|       2 |     4 | 2013-05-23 07:36:15 |
|       1 |     2 | 2013-05-24 11:55:02 |
+---------+-------+---------------------+
4

2 回答 2

1

这有点复杂。首先，您需要的是每条记录的下一个事件的时间。nexted如果在范围内，以下子查询会添加这样的时间 ( )：

 select t.*,
         (select event_date
          from t t2
          where t2.item_id = t.item_id and
                t2.event_date > t.event_date and
                <date comparison here>
          order by event_date limit 1
         ) as nexted
  from t

这使用相关子查询。<date comparison here>用于您想要的任何日期比较。当没有记录时，该值将为 NULL。

现在，有了这些信息 ( nexted)，就有了获得分组的技巧。对于任何记录，它是之后的第一个事件时间，其中nexted为 NULL。这将是该系列的最后一场活动。不幸的是，这需要两个级别的嵌套相关子查询（或聚合连接）。结果看起来有点笨拙：

select item_id, GROUPING, MIN(event_date) as start_date, MAX(event_date) as end_date,
       COUNT(*) as num_dates
from (select t.*,
             (select min(t2.event_date)
              from (select t1.*,
                           (select event_date
                            from t t2
                            where t2.item_id = t1.item_id and
                                  t2.event_date > t1.event_date and
                                  <date comparison here>
                            order by event_date limit 1
                           ) as nexted
                    from t1
                   ) t2
              where t2.nexted is null
             ) as grouping
      from t
     ) s
group by item_id, grouping;
于 2013-05-17T20:27:30.873 回答
0

如何通过查找每个单独记录的本地关联来接近它，然后根据每个记录的发现对最大事件日期进行分组。这是基于静态差分时间间隔（在我的示例中为 5 分钟）

SELECT item_id, MAX(total), MAX(last_date_in_group) AS last_date_in_group FROM (
    SELECT t1.item_id, COUNT(*) AS total, COALESCE(GREATEST(t1.event_date, MAX(t2.event_date)), t1.event_date) AS last_date_in_group
        FROM table_name t1
        LEFT JOIN table_name t2 ON t2.event_date BETWEEN t1.event_date AND t1.event_date + INTERVAL 5 MINUTE
        GROUP BY t1.id
    ) t
    GROUP BY last_date_in_group
于 2013-05-17T20:19:02.907 回答