我正在计算在一块土地上灌溉的总水量。我所拥有的是在记录到SQL数据库中的瞬间流量的变化。 - 这是以每小时立方米计算的。
Date Time Flow Value
2009/10/22 04:00:00.0 0
2009/10/22 04:00:16.2 23
2009/10/22 04:00:20.6 34
2009/10/22 04:00:39.7 95
2009/10/22 04:00:41.7 97
2009/10/22 04:01:15.1 110
2009/10/22 04:03:17.0 95
2009/10/22 04:06:53.8 82
2009/10/22 04:26:50.7 77
2009/10/22 04:36:50.8 76
2009/10/22 04:46:51.7 72
2009/10/22 04:56:52.2 74
2009/10/22 05:16:52.7 72
2009/10/22 05:26:53.2 70
2009/10/22 05:36:22.1 84
2009/10/22 05:46:16.3 81
2009/10/22 05:56:16.2 75
2009/10/22 06:16:17.3 73
2009/10/22 06:26:16.9 75
2009/10/22 06:36:17.7 71
2009/10/22 06:57:38.7 57
2009/10/22 06:57:48.9 44
2009/10/22 06:57:53.4 28
2009/10/22 06:57:55.3 12
2009/10/22 07:07:55.1 0
简单地说，不是总结这些值，并假设这是灌溉水的总量。
需要做的是计算每个时间戳的时差并计算该持续时间的音量，然后将其用于用户选择的小时数。
因此对于上述数据，那么时间差将是（第一个小时）
time diff volume
00:00:04.4 101.20
00:00:19.1 649.40
00:00:02.0 190.00
00:00:33.5 3249.50
00:02:01.9 13409.00
00:03:36.8 20596.00
00:19:56.9 98145.80
00:10:00.1 46207.70
00:10:00.9 45668.40
00:10:00.5 43236.00
00:20:00.5 88837.00
00:10:00.5 13521.60
那小时灌溉的总量（凌晨4点到凌晨5点）是：373811.6立方米的水除以3600 = 103.8365556
问题是：我如何用SQL做到这一点 - 我完全迷失了，不知道从哪里开始，任何帮助都会受到赞赏
答案 0 :(得分：2)
此答案假设您使用的是SQL Server。你的样本“第一个小时”实际上包括超过第一个小时;它应该在我认为00：10：00排之后停止。
您可以通过将表连接到自身，然后加入另一个时间，然后在前两行之间没有任何内容，找到每行的上一行：
select
StartDate = prev.date
, EndDate = cur.date
, Milliseconds = datediff(ms,prev.date,cur.date)
, Volume = datediff(ms,prev.date,cur.date) / 1000.0 * prev.flow
from @flow cur
inner join @flow prev
on prev.date < cur.date
left join @flow inbetween
on prev.date < inbetween.date
and inbetween.date < cur.date
where inbetween.date is null
这为您提供每期的总和。计算小时总计要求您拆分跨越一小时边界的条目。您可以通过在每小时结束时添加一个条目来完成此操作，例如：
select date, flow
from @flow
union
-- Add end of hour
select DATEADD(Hour, DATEDIFF(Hour, 0, date)+1, 0), flow
from @flow
where date in (select max(date) from @flow group by datepart(hh,date))
您可以使用WITH语句组合两个查询来计算每小时的总和：
;with FlowWithHourBounds as (
select date, flow
from @flow
union
-- Add end of hour
select DATEADD(Hour, DATEDIFF(Hour, 0, date)+1, 0), flow
from @flow
where date in (
select max(date) from @flow group by datepart(hh,date))
)
, FlowPerPeriod as (
select
StartDate = prev.date
, EndDate = cur.date
, Milliseconds = datediff(ms,prev.date,cur.date)
, Volume = datediff(ms,prev.date,cur.date) / 1000.0 * prev.flow
from FlowWithHourBounds cur
inner join FlowWithHourBounds prev
on prev.date < cur.date
left join FlowWithHourBounds inbetween
on prev.date < inbetween.date
and inbetween.date < cur.date
where inbetween.date is null
)
select datepart(hh,StartDate), sum(Volume)
from FlowPerPeriod
group by datepart(hh,StartDate)
结果是：
hour volume
4 285340,5
5 273288,5
6 255408,3
7 5701,2
以下是我在帖子中创建的示例数据集：
declare @flow table ([date] datetime, flow float)
insert into @flow values ('2009/10/22 04:00:00.0', 0 )
insert into @flow values ('2009/10/22 04:00:16.2', 23 )
insert into @flow values ('2009/10/22 04:00:20.6', 34 )
insert into @flow values ('2009/10/22 04:00:39.7', 95 )
insert into @flow values ('2009/10/22 04:00:41.7', 97 )
insert into @flow values ('2009/10/22 04:01:15.1', 110)
insert into @flow values ('2009/10/22 04:03:17.0', 95 )
insert into @flow values ('2009/10/22 04:06:53.8', 82 )
insert into @flow values ('2009/10/22 04:26:50.7', 77 )
insert into @flow values ('2009/10/22 04:36:50.8', 76 )
insert into @flow values ('2009/10/22 04:46:51.7', 72 )
insert into @flow values ('2009/10/22 04:56:52.2', 74 )
insert into @flow values ('2009/10/22 05:16:52.7', 72 )
insert into @flow values ('2009/10/22 05:26:53.2', 70 )
insert into @flow values ('2009/10/22 05:36:22.1', 84 )
insert into @flow values ('2009/10/22 05:46:16.3', 81 )
insert into @flow values ('2009/10/22 05:56:16.2', 75 )
insert into @flow values ('2009/10/22 06:16:17.3', 73 )
insert into @flow values ('2009/10/22 06:26:16.9', 75 )
insert into @flow values ('2009/10/22 06:36:17.7', 71 )
insert into @flow values ('2009/10/22 06:57:38.7', 57 )
insert into @flow values ('2009/10/22 06:57:48.9', 44 )
insert into @flow values ('2009/10/22 06:57:53.4', 28 )
insert into @flow values ('2009/10/22 06:57:55.3', 12 )
insert into @flow values ('2009/10/22 07:07:55.1', 0 )
答案 1 :(得分：1)
WITH differences
AS (
SELECT s.dt AS dt_start
,MIN(e.dt) AS dt_end
,DATEDIFF(ms, s.dt, MIN(e.dt)) / 1000.0 AS seconds
FROM so1608779 AS s
INNER JOIN so1608779 AS e
ON e.dt > s.dt
GROUP BY s.dt
),
results1
AS (
SELECT differences.*
,so1608779.flow
,so1608779.flow * differences.seconds AS volume
,ROW_NUMBER() OVER (ORDER BY differences.dt_start) AS row
FROM differences
INNER JOIN so1608779
ON so1608779.dt = differences.dt_start
)
SELECT *
,(
SELECT SUM(volume)
FROM results1 AS x
WHERE x.row <= results1.row
) AS running_total
FROM results1
答案 2 :(得分：0)
你可以从这开始：
declare @table table (_time datetime, flow int)
insert into @table
select '04:00:00.0', 0
union select '04:00:16.2', 23
union select '04:00:20.6', 34
union select '04:00:39.7', 95
union select '04:00:41.7', 97
union select '04:01:15.1', 110
union select '04:03:17.0', 95
union select '04:06:53.8', 82
union select '04:26:50.7', 77
union select '04:36:50.8', 76
union select '04:46:51.7', 72
union select '04:56:52.2', 74
union select '05:16:52.7', 72
union select '05:26:53.2', 70
union select '05:36:22.1', 84
union select '05:46:16.3', 81
union select '05:56:16.2', 75
union select '06:16:17.3', 73
union select '06:26:16.9', 75
union select '06:36:17.7', 71
union select '06:57:38.7', 57
union select '06:57:48.9', 44
union select '06:57:53.4', 28
union select '06:57:55.3', 12
union select '07:07:55.1', 0
select t1._time time_start, t2._time time_finish, t1.flow
from @table t1, @table t2
where t2._time = (select min(_time) from @table where _time > t1._time)
这将返回一行中的间隔和值：
time_start time_finish flow
04:00:00.000 04:00:16.200 0
04:00:16.200 04:00:20.600 23
04:00:20.600 04:00:39.700 34
04:00:39.700 04:00:41.700 95
04:00:41.700 04:01:15.100 97
04:01:15.100 04:03:17.000 110
04:03:17.000 04:06:53.800 95
04:06:53.800 04:26:50.700 82
04:26:50.700 04:36:50.800 77
04:36:50.800 04:46:51.700 76
04:46:51.700 04:56:52.200 72
04:56:52.200 05:16:52.700 74
05:16:52.700 05:26:53.200 72
05:26:53.200 05:36:22.100 70
05:36:22.100 05:46:16.300 84
05:46:16.300 05:56:16.200 81
05:56:16.200 06:16:17.300 75
06:16:17.300 06:26:16.900 73
06:26:16.900 06:36:17.700 75
06:36:17.700 06:57:38.700 71
06:57:38.700 06:57:48.900 57
06:57:48.900 06:57:53.400 44
06:57:53.400 06:57:55.300 28
06:57:55.300 07:07:55.100 12
在此之后，您可以像子查询一样使用它并进行一些乘法和求和。
当然这是一个简化的例子。