对 SQL 中多行的日期求和？

Question

我们有一个 Table 存储系统中某些设定点的警报。我正在尝试编写一个查询，首先获取两个日期之间的差异（分布在两行中），然后对所有日期差异求和以获得设定点处于警报状态的时间量的总和。

我们有一个数据库，我在其中完成了类似的操作，但在那种情况下，startTime 和 endTime 都在同一行。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，然后我需要获取报警的总时间。我认为 CTE 可能会有所帮助，但我不确定。

我相信伪查询逻辑类似于

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

Answer 1

您可以使用 LEAD 窗口函数（或 LAG）轻松完成此操作。这假设行总是成对出现，"InAlarm" 为 1-0-1-0。如果那没有发生，那么它将把事情扔掉。在任何情况下，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

Answer 2

一种简单的方法是使用 OUTER APPLY 获取下一个不是 InAlarm 的日期

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

LEAD() 如果使用 MSSQL 2012+

可能会表现更好

Answer 3

在 SQL 服务器 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

这将过滤掉具有相同警报状态的连续事件

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