Tangkap waktu mulai dan berakhir untuk perubahan status bidang

Jika Anda memiliki SQL Server 2012 atau yang lebih baru maka Anda dapat menggunakan fungsi windowing SQL Server untuk mendapatkan hasil yang diinginkan sebagai berikut:

CREATE TABLE [dbo].[EventStates](
    [Item] [varchar](1) NOT NULL,
    [EventDate] [varchar](19) NOT NULL,
    [Event] [varchar](3) NOT NULL
) ON [PRIMARY]

GO

INSERT [dbo].[EventStates] ([Item], [EventDate], [Event]) VALUES (N'A', N'2011-10-03 00:01:00', N'On')
INSERT [dbo].[EventStates] ([Item], [EventDate], [Event]) VALUES (N'A', N'2011-10-03 00:01:15', N'On')
INSERT [dbo].[EventStates] ([Item], [EventDate], [Event]) VALUES (N'B', N'2011-10-03 00:01:00', N'On')
INSERT [dbo].[EventStates] ([Item], [EventDate], [Event]) VALUES (N'A', N'2011-10-03 00:02:00', N'Off')
INSERT [dbo].[EventStates] ([Item], [EventDate], [Event]) VALUES (N'A', N'2011-10-03 00:02:01', N'Off')
INSERT [dbo].[EventStates] ([Item], [EventDate], [Event]) VALUES (N'C', N'2011-10-03 00:01:00', N'On')
INSERT [dbo].[EventStates] ([Item], [EventDate], [Event]) VALUES (N'B', N'2011-10-03 00:02:00', N'Off')
INSERT [dbo].[EventStates] ([Item], [EventDate], [Event]) VALUES (N'A', N'2011-10-03 00:02:02', N'On')
INSERT [dbo].[EventStates] ([Item], [EventDate], [Event]) VALUES (N'C', N'2011-10-03 00:02:05', N'On')
INSERT [dbo].[EventStates] ([Item], [EventDate], [Event]) VALUES (N'A', N'2011-10-03 00:02:07', N'Off')

GO

;WITH StateChange
AS
(
    SELECT   E.[Item]
            ,E.[EventDate]
            ,E.[Event]
            ,(  -- First determine if a state change to on has occurred.
                CASE
                    WHEN E.[Event] = 'On' AND LAG(E.[Event], 1, NULL) OVER (PARTITION BY E.[Item] ORDER BY E.[EventDate] ASC) IS NULL THEN 1
                    WHEN E.[Event] = 'On' AND E.[Event] <> LAG(E.[Event], 1, NULL) OVER (PARTITION BY E.[Item] ORDER BY E.[EventDate] ASC) THEN 1
                    ELSE 0
                END
             ) [StateChanged]
    FROM    EventStates E
), StateChangeGrouping
AS
(
    SELECT   [Item]
            ,[EventDate]
            ,[Event]
            ,[StateChanged]
            ,SUM([StateChanged]) OVER (PARTITION BY [Item] ORDER BY [EventDate] ASC) AS [GroupID]
    FROM    StateChange 
), StateChangeRanked
AS
(
    SELECT   [Item]
            ,[EventDate]
            ,[Event]
            ,[StateChanged]
            ,[GroupID]
            ,ROW_NUMBER() OVER (PARTITION BY [Item], GroupID, [Event] ORDER BY [EventDate]) AS TransitionRank
    FROM    StateChangeGrouping
)
SELECT      [Item]
            ,MIN([EventDate]) AS [Start]
            ,MAX([EventDate]) AS [End]
            ,[GroupID]
FROM        StateChangeRanked
WHERE       GroupID > 0 AND TransitionRank = 1
GROUP BY    [Item], GroupID
ORDER BY    [Item], [Start]

Di bawah ini adalah implementasi untuk SQL Server 2008.

;WITH EventID
AS
(
    SELECT   ROW_NUMBER() OVER(PARTITION BY [Item] ORDER BY [EventDate]) RowNr
            ,[Item]
            ,[EventDate]
            ,[Event] 
    FROM    [dbo].[EventStates]
), StateChange
AS
(
    SELECT  C.RowNr
            ,P.RowNr AS P_RowNr
            ,C.[Item]
            ,C.[EventDate]
            ,C.[Event] 
            ,P.[Event] AS P_Event
            ,(  -- First determine if a state change to on has occurred.
                CASE
                    WHEN C.[Event] = 'On' AND P.[Event] IS NULL THEN 1
                    WHEN C.[Event] = 'On' AND C.[Event] <> P.[Event] THEN 1
                    ELSE 0
                END
                ) [StateChanged]
    FROM    EventID C
    LEFT OUTER JOIN EventID P ON C.Item = P.Item AND C.RowNr = P.RowNr + 1
), StateChangeGrouping
AS
(
    SELECT   ST1.[Item]
            ,ST1.[EventDate]
            ,ST1.[Event]
            ,ST1.[StateChanged]
            ,(
                SELECT SUM([StateChanged])
                FROM StateChange ST2
                WHERE ST2.Item = ST1.Item AND ST2.RowNr <= ST1.RowNr
             ) AS GroupID
    FROM    StateChange ST1
), StateChangeRanked
AS
(
    SELECT   [Item]
            ,[EventDate]
            ,[Event]
            ,[StateChanged]
            ,[GroupID]
            ,ROW_NUMBER() OVER (PARTITION BY [Item], GroupID, [Event] ORDER BY [EventDate]) AS TransitionRank
    FROM    StateChangeGrouping
)
SELECT      [Item]
            ,MIN([EventDate]) AS [Start]
            ,MAX([EventDate]) AS [End]
            ,[GroupID]
FROM        StateChangeRanked
WHERE       GroupID > 0 AND TransitionRank = 1
GROUP BY    [Item], GroupID
ORDER BY    [Item], [Start]