Question

我们有一个Table，用于存储系统中某些SetPoints的警报。我正在尝试编写一个查询，首先得到两个日期之间的差异（分布在两行），然后将所有日期差异相加，得到设定点处于警报状态的时间总和。

我们有一个数据库，我已经完成了类似的工作，但在这种情况下，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) |

基本上，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，然后我需要获得警报的总时间。我是CTE可以帮助的东西，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。这假设对于“InAlarm”，行总是与1-0-1-0成对出现。如果这种情况没有发生，那么就会把事情搞砸。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来获取非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 +

，

LEAD()可能会表现更好

Answer 3

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

这将过滤掉具有相同警报状态的连续事件

在SQL中对多行进行求和？

3 个答案: