T-SQL Start and end date times from a single column

Question

I have a single table of on/off events for different assets. I need to get a list of start & stop event times without using a cursor.

Source:

Item          


        

Answer 1

declare @YourTable table (Item varchar(10), EventDate datetime, Event varchar(10)) 

insert into @YourTable values 
('A','2011-10-03 00:01:00''On'), 
('B','2011-10-03 00:01:00','On'), 
('A','2011-10-03 00:02:00','Off'), 
('C','2011-10-03 00:01:00','On'), 
('B','2011-10-03 00:02:00','Off'), 
('A','2011-10-03 00:02:02','On'),   
('C','2011-10-03 00:02:05','Off'), 
('A','2011-10-03 00:02:07','Off'), 
('D','2011-10-03 00:02:02','On')   

;with a as
(
select item, eventdate, event, ROW_NUMBER() Over(Partition by Item order by EventDate) RN 
from @YourTable
),
b as (
select item, eventdate, 0 e, rn, event from a where rn = 1
union all
select b.item, a.eventdate, case when b.event = 'Off' then b.e+1 else b.e end, a.rn, a.event
from b 
join a on b.rn + 1 = a.rn and a.item = b.item
)
select item, min(eventdate) Start, max(eventdate) [End]
 from b
group by item, e
order by item, e