Veja SQL Fiddle aqui .
with tbl as (
-- this will generate daily merged ovelaping time
select distinct
a.id
,(
select min(x.starttime)
from act x
where x.id=a.id and ( x.starttime between a.starttime and a.endtime
or a.starttime between x.starttime and x.endtime )
) start1
,(
select max(x.endtime)
from act x
where x.id=a.id and ( x.endtime between a.starttime and a.endtime
or a.endtime between x.starttime and x.endtime )
) end1
from act a
), tbl2 as
(
-- this will add minute and total minute column
select
*
,datediff(mi,t.start1,t.end1) mi
,(select sum(datediff(mi,x.start1,x.end1)) from tbl x where x.id=t.id and x.end1<=t.end1) totalmi
from tbl t
), tbl3 as
(
-- now final query showing starttime and endtime for 5 hours other wise null in case not completed 5(300 minutes) hours
select
t.id
,min(t.start1) starttime
,min(case when t.totalmi>300 then t.end1 else null end) endtime
from tbl2 t
group by t.id
)
-- final result
select *
from tbl3
where endtime is not null
