[英]Summing dates across multiple rows in SQL?
我们有一个表,用于存储系统中某些设定点的警报。 我正在尝试编写一个查询,该查询首先获取两个日期之间的差(分布在两行中),然后将所有日期差求和,以求出设定值处于警报状态的总时间。
我们有一个数据库,我已经完成了类似的工作,但是在那种情况下,startTime和endTime都在同一行中。 在这种情况下,这是不够的
一些示例数据
| Row | TagID | SetPointID | EventLogTime | InAlarm |
-------------------------------------------------------------------------------------
| 1 | 1 | 2 | 2016-01-01 01:49:18.070 | 1 |
| 2 | 1 | 1 | 2016-01-01 03:23:39.970 | 1 |
| 3 | 1 | 2 | 2016-01-01 03:23:40.070 | 0 |
| 4 | 1 | 1 | 2016-01-01 08:04:01.260 | 0 |
| 5 | 1 | 2 | 2016-01-01 08:04:01.370 | 1 |
| 6 | 1 | 1 | 2016-01-01 11:40:36.367 | 1 |
| 7 | 1 | 2 | 2016-01-01 11:40:36.503 | 0 |
| 8 | 1 | 1 | 2016-01-01 13:00:30.263 | 0 |
结果
| TagID | SetPointID | TotalTimeInAlarm |
------------------------------------------------------
| 1 | 1 | 6.004443 (hours) |
| 1 | 2 | 5.182499 (hours) |
本质上,我需要做的是获取每个标签和每个设定点的开始时间和结束时间,然后我需要获取警报中的总时间。 我认为CTE可以提供帮助,但是我不确定。
我相信伪查询逻辑将类似于
Define @startTime DATETIME, @endTime DATETIME
SELECT TagID,
SetPointID,
ABS(First Occurrence of InAlarm = True (since last occurrence WHERE InAlarm = False)
- First Occurrence of InAlarm = False (since last occurrence WHERE InAlarm = True))
-- IF no InAlarm = False use @endTime.
GROUP BY TagID, SetPointID
您可以使用LEAD
窗口功能(或LAG
)轻松完成此操作。 假设“ InAlarm”的行始终与1-0-1-0成对出现。 如果那没有发生,那将丢掉东西。 无论如何,您都需要针对这些情况制定业务规则。
;WITH CTE_Timespans AS
(
SELECT
TagID,
SetPointID,
InAlarm,
EventLogTime,
LEAD(EventLogTime, 1) OVER (PARTITION BY TagID, SetPointID ORDER BY EventLogTime) AS EndingEventLogTime
FROM
My_Table
)
SELECT
TagID,
SetPointID,
SUM(DATEDIFF(SS, EventLogTime, EndingEventLogTime))/3600.0 AS TotalTime
FROM
CTE_Timespans
WHERE
InAlarm = 1
GROUP BY
TagID,
SetPointID
一种简单的方法是使用OUTER APPLY获取不是InAlarm的下一个日期
SELECT mt.TagID,
mt.SetPointID,
SUM(DATEDIFF(ss,mt.EventLogTime,oa.EventLogTime)) / 3600.0 AS [TotalTimeInAlarm]
FROM MyTable mt
OUTER APPLY (SELECT MIN([EventLogTime]) EventLogTime
FROM MyTable mt2
WHERE mt.TagID = mt2.TagID
AND mt.SetPointID = mt2.SetPointID
AND mt2.EventLogTime > mt.EventLogTime
AND InAlarm = 0
) oa
WHERE mt.InAlarm = 1
GROUP BY mt.TagID,
mt.SetPointID
如果使用MSSQL 2012+,则LEAD()
可能更高
在SQL Server 2014+中:
SELECT tagId, setPointId, SUM(DATEDIFF(second, pt, eventLogTime)) / 3600. AS diff
FROM (
SELECT *,
LAG(inAlarm) OVER (PARTITION BY tagId, setPointId ORDER BY eventLogTime, row) ppa,
LAG(eventLogTime) OVER (PARTITION BY tagId, setPointId ORDER BY eventLogTime, row) pt
FROM (
SELECT LAG(inAlarm) OVER (PARTITION BY tagId, setPointId ORDER BY eventLogTime, row) pa,
*
FROM mytable
) q
WHERE EXISTS
(
SELECT pa
EXCEPT
SELECT inAlarm
)
) q
WHERE ppa = 0
AND inAlarm = 1
GROUP BY
tagId, setPointId
这将过滤出具有相同警报状态的连续事件
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