Lijst met begin- en eindwaarden ophalen uit de tabel met datetimes

-- Table var to store the gaps
declare @T table
(
  DeviceID varchar(10),
  PrevPeriodEnd datetime,
  NextPeriodStart datetime
)

-- Get the gaps
;with cte as 
(
  select *,
    row_number() over(partition by DeviceID order by Timestamp) as rn
  from data
)
insert into @T
select
  C1.DeviceID,
  C1.Timestamp as PrevPeriodEnd,
  C2.Timestamp as NextPeriodStart
from cte as C1
  inner join cte as C2
    on C1.rn = C2.rn-1 and
       C1.DeviceID = C2.DeviceID and
       datediff(s, C1.Timestamp, C2.Timestamp) > 5

-- Build islands from gaps in @T
;with cte1 as
(
  -- Add first and last timestamp to gaps
  select DeviceID, PrevPeriodEnd, NextPeriodStart
  from @T
  union all
  select DeviceID, max(TimeStamp) as PrevPeriodEnd, null as NextPeriodStart
  from data
  group by DeviceID
  union all
  select DeviceID, null as PrevPeriodEnd, min(TimeStamp) as PrevPeriodEnd
  from data
  group by DeviceID
),
cte2 as
(
  select *,
    row_number() over(partition by DeviceID order by PrevPeriodEnd) as rn
  from cte1
)
select
  C1.DeviceID,
  C1.NextPeriodStart as PeriodStart,
  C2.PrevPeriodEnd as PeriodEnd
from cte2 as C1
  inner join cte2 as C2
    on C1.DeviceID = C2.DeviceID and
       C1.rn = C2.rn-1
order by C1.DeviceID, C1.NextPeriodStart