datetime, Sql Server

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DECLARE @SampleData AS TABLE
    (
	   [Datetime] datetime,
	   AgentID varchar(10),
	   Workstate varchar(500)
    )

INSERT INTO @SampleData
    VALUES
    ('2017-03-01 09:55:00','RAR','Customer Service'),
    ('2017-03-01 10:18:00','RAR','Retention'),
    ('2017-03-01 10:30:00','RAR','Customer Service'),
    ('2017-03-01 10:45:00','RAR','Mail'),
    ('2017-03-01 11:00:00','RAR','Customer Service'),
    ('2017-03-01 11:53:00','RAR','Logged out')

DECLARE @MinDate datetime =  (SELECT min(sd.[Datetime]) FROM @SampleData sd)
    DECLARE @MaxDate datetime =  (SELECT max(sd.[Datetime]) FROM @SampleData sd)

;WITH temp AS
    (
	   SELECT CAST('2017-03-01 00:00:00' AS datetime)  AS IntervalDate

UNION ALL

SELECT dateadd(minute,15, t.IntervalDate) AS IntervalDate 
	   FROM temp t
	   WHERE t.IntervalDate < @MaxDate
    )
    SELECT 
		  CASE WHEN sd.Datetime < cr.IntervalDate THEN sd.Datetime ELSE cr.IntervalDate END AS [Datetime Start],
		  CASE WHEN sd.Datetime < cr.IntervalDate THEN cr.IntervalDate ELSE sd.Datetime END AS [Datetime End],
		  sd.AgentID, 
		  sd.Workstate
    FROM @SampleData sd
    CROSS APPLY
    (
	   SELECT * 
	   FROM temp t
	   WHERE	  t.IntervalDate >= @MinDate
			 AND (	
				    datediff(minute, t.IntervalDate, sd.Datetime) BETWEEN 0 AND 15
				    OR datediff(minute, sd.Datetime, t.IntervalDate) BETWEEN 0 AND 15
				)

) cr
    
    OPTION (MAXRECURSION 0)

View schema
Execution time: 0,02 sec, rows selected: 16, rows affected: 6, absolute service time: 0,17 sec