calculate days with gaps - sql-server

Question

table:
+-----------+--------------+------------+------------+
| RequestID | RequestStaus | StartDate | EndDate |
+-----------+--------------+------------+------------+
| 1 | pending | 9/1/2015 | 10/2/2015 |
| 1 | in progress | 10/2/2015 | 10/20/2015 |
| 1 | completed | 10/20/2015 | 11/3/2015 |
| 1 | reopened | 11/3/2015 | null |
| 2 | pending | 9/5/2015 | 9/7/2015 |
| 2 | in progress | 9/7/2015 | 9/25/2015 |
| 2 | completed | 9/25/2015 | 10/7/2015 |
| 2 | reopened | 10/10/2015 | 10/16/2015 |
| 2 | completed | 10/16/2015 | null |
+-----------+--------------+------------+------------+
I would like to calculate the days opened but exclude the days between completed and reopened. For example, RequestID 1, the days opened will be (11/3/2015 - 9/1/2015) + (GetDate() - 11/3/2015), for request 2, the total days will be (10/7/2015 - 9/5/2015) + ( 10/16/2015 - 10/10/2015).
The result I want will be something like:
+-----------+-------------------------------+
| RequestID | DaysOpened |
+-----------+-------------------------------+
| 1 | 63 + (getdate() - 11/3/2015) |
| 2 | 38 |
+-----------+-------------------------------+
How do I approach this problem? thank you!

Answer 1

Tested. Works well. :)
Note:
1) I suppose the required result = (FirstCompleteEndDate - PendingStartDate)+(Sum of all the Reopen duration)
2) So I used the self joins. Table b provides the exact completed record which immediately follows the in process record for each RequestID. Table c provides Sum of all the Reopen duration.
--create tbl structure
create table #test (RequestID int, RequestStatus varchar(20), StartDate date, EndDate date)
go
--insert sample data
insert #test
select 1,'pending','09/01/2015','10/2/2015'
union all
select 1,'in progress','10/2/2015','10/20/2015'
union all
select 1,'completed','10/20/2015','11/3/2015'
union all
select 1,'reopened','11/3/2015',null
union all
select 2,'pending','09/05/2015','9/7/2015'
union all
select 2,'in progress','09/07/2015','9/25/2015'
union all
select 2,'completed','9/25/2015','10/7/2015'
union all
select 2,'reopened','10/10/2015','10/16/2015'
union all
select 2, 'completed','10/16/2015','11/12/2015'
union all
select 2,'reopened','11/20/2015',null
select * from #test
--below is solution
select a.RequestID, a.Startdate as [PendingStartDate], b.enddate as [FirstCompleteEndDate], c.startdate as [LatestReopenStartDate],
datediff(day,a.startdate,b.enddate)+c.ReopenDays as [days] from #test a
join (
select *, row_number()over(partition by RequestID,RequestStatus order by StartDate) as rid from #test
) as b
on a.RequestID = b.RequestID
join (
select distinct RequestID, RequestStatus, max(StartDate)over(partition by RequestID,RequestStatus) as StartDate,
Sum(Case when enddate is null then datediff(day,startdate,getdate())
when enddate is not null then datediff(day,startdate,enddate)
end)over(partition by RequestID,RequestStatus) as [ReopenDays]
from #test
where RequestStatus = 'reopened'
) as c
on b.RequestID = c.RequestID
where a.RequestStatus ='pending' and b.RequestStatus = 'completed' and b.rid = 1
Result: