在SQL中跨多行匯總日期？

Question

我們有一個表，用於存儲系統中某些設定點的警報。 我正在嘗試編寫一個查詢，該查詢首先獲取兩個日期之間的差（分布在兩行中），然后將所有日期差求和，以求出設定值處於警報狀態的總時間。

我們有一個數據庫，我已經完成了類似的工作，但是在那種情況下，startTime和endTime都在同一行中。 在這種情況下，這是不夠的

一些示例數據

|   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      |

結果

|   TagID    |   SetPointID   |   TotalTimeInAlarm   |
------------------------------------------------------
|     1      |        1       |    6.004443  (hours) |
|     1      |        2       |    5.182499  (hours) |

本質上，我需要做的是獲取每個標簽和每個設定點的開始時間和結束時間，然后我需要獲取警報中的總時間。 我認為CTE可以提供幫助，但是我不確定。

我相信偽查詢邏輯將類似於

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窗口功能（或LAG ）輕松完成此操作。 假設“ InAlarm”的行始終與1-0-1-0成對出現。 如果那沒有發生，那將丟掉東西。 無論如何，您都需要針對這些情況制定業務規則。

;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

一種簡單的方法是使用OUTER APPLY獲取不是InAlarm的下一個日期

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+，則LEAD()可能更高

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

這將過濾出具有相同警報狀態的連續事件