create table dbo.AgentLog (
	 AgentID	int
	,LogInTime	datetime
	,LogOutTime	datetime
	)
go

insert dbo.AgentLog
select 1, '2010-09-08 09:40:00.000', '2010-09-08 10:14:00.000'
union all 
select 1, '2010-09-08 10:35:00.000', '2010-09-08 12:04:00.000'
union all 
select 1, '2010-09-08 13:11:00.000', '2010-09-08 14:24:00.000'
union all 
select 1, '2010-09-08 14:35:00.000', '2010-09-08 16:08:00.000'
union all 
select 2, '2010-09-08 09:00:00.000', '2010-09-08 09:23:00.000'
union all 
select 2, '2010-09-08 10:12:00.000', '2010-09-08 12:05:00.000'
union all 
select 2, '2010-09-08 13:12:00.000', '2010-09-08 15:07:00.000'
union all 
select 2, '2010-09-08 15:10:00.000', '2010-09-08 16:25:00.000'
go

;with AgentLogCTE as
(select Row_Number() over (partition by AgentID order by LogInTime) as RowID, * from dbo.AgentLog )

select * from AgentLogCTE
go

;with AgentLogCTE as
(select Row_Number() over (partition by AgentID order by LogInTime) as RowID, * from dbo.AgentLog )

select
	 t1.AgentID
	,t2.LogOutTime as PrevLogout
	,t1.LogInTime as Login
	,convert(varchar, t1.LogInTime - t2.LogOutTime, 108) as BreakTime
from AgentLogCTE t1
	join AgentLogCTE t2 
		on t2.RowID = (t1.RowID-1) and t1.AgentID = t2.AgentID
go

drop table dbo.AgentLog
go