记录之间经过的平均时间

Question

我有一张车载表 - id和他们的电池电量 - battery，每隔十分钟收集一次。

我的目标是以下输出：电池从100减少到0所需的平均时间。我的目标是获取所有汽车ID的全局平均值，即battery = 100和battery = 0所有独特的平均时差IDS。一个小警告是0必须在100之后，换句话说，我想排除充电时间（当100之后会出现0）。

如何在psql中编写这样的查询？

以下是一辆汽车的数据示例：

  id|                           time| battery
 54 | 2017-12-12 09:50:04.402775+00 |     100
 54 | 2017-12-12 09:40:04.618926+00 |     100
 54 | 2017-12-12 09:30:04.11399+00  |     100
 54 | 2017-12-12 09:20:03.906716+00 |     100
 54 | 2017-12-12 09:10:03.955133+00 |     100
 54 | 2017-12-12 09:00:04.678508+00 |     100
 54 | 2017-12-12 08:50:03.733471+00 |     100
 54 | 2017-12-12 08:40:03.65688+00  |     100
 54 | 2017-12-12 08:30:04.260608+00 |     100
 54 | 2017-12-12 08:20:03.98387+00  |     100
 54 | 2017-12-12 08:10:04.164129+00 |      98
 54 | 2017-12-12 08:00:04.597976+00 |      98
 54 | 2017-12-12 07:50:04.501231+00 |      98
 54 | 2017-12-12 07:40:04.441531+00 |      98
 54 | 2017-12-12 07:30:04.310876+00 |      98
 54 | 2017-12-12 07:20:04.317241+00 |      98
 54 | 2017-12-12 07:10:03.856432+00 |      67
 54 | 2017-12-12 07:00:03.628862+00 |      67
 54 | 2017-12-12 06:50:03.868495+00 |      67
 54 | 2017-12-12 06:40:04.490324+00 |      67
 54 | 2017-12-12 06:30:03.83739+00  |      67
 54 | 2017-12-12 06:20:03.817014+00 |      67
 54 | 2017-12-12 06:10:04.081174+00 |      29
 54 | 2017-12-12 06:00:04.178765+00 |      29





    data_type         
--------------------------
 integer
 timestamp with time zone
 integer

Answer 1

所以，你只想要在下一个100之前有0的100。

select avg(extract(epoch from (next_time - time) ) as avg_recharge_time
from (select t.*,
             lead(battery) over (partition by id order by time) as next_battery,
             lead(time) over (partition by id order by time) as next_time
      from t
      where battery in (0, 100)
     ) t
where battery = 100 and next_battery = 0;

这回答了您提出的问题。然而。我可以想象你的情况更复杂。例如，如果电池可以部分充电，那么这将产生不正确的结果。如果您遇到类似情况，请提出其他问题，并提供合适的样本数据和说明。