View and complex query count distinct locations employee stayed in SQL - sql

Question

I have a view which looks like this view_1:
id Office Begin_dt Last_dt Days
1 Office1 2019-09-02 2019-09-08 6
1 Office2 2019-09-09 2019-09-30 21
1 Office1 2019-10-01 2019-10-31 30
5 Office3 2017-10-01 2017-10-16 15
5 Office2 2017-10-17 2017-10-30 13
5 Office2 2017-11-01 2017-11-31 30
I want to find the office where employee stayed for max time and also the number of Distinct Office locations he stayed in.
Expected output
id Max_time_in_Office Days Distinct_office_locations
1 Office1 36 2
5 Office2 43 2
So id 1 spends 6 and 30, overall 36 days in office 1. Max time is spent in office 1 by him. Distinct locations are 2.
id 5 spends 13 and 30 , 43 days in office. Max time is spent in office 2. Distinct locations are 2.
Code tried
select v.*
from (select v.id, v.office, sum(days) as Max_time_in_Office, count(Office) as Distinct_office_locations,
rank() over (partition by id order by sum(days) desc) as seqnum
from view_1 v
group by id, office
) v
where seqnum = 1;
Output obtained
id Max_time_in_Office Days Distinct_office_locations
1 Office1 36 1
5 Office2 43 1
So I am getting wrong output. Can someone pls help

Answer 1

Close. You want a window function:
select v.*
from (select v.id, v.office, sum(days) as Max_time_in_Office,
count(*) over (partition by id) as Distinct_office_locations,
rank() over (partition by id order by sum(days) desc) as seqnum
from view_1 v
group by id, office
) v
where seqnum = 1;
Basically the window function is counting the number of rows returned after the aggregation -- and there is one row per office.

Answer 2

You could use the apply operator to achieve that:
select V.Id,
T.Max_Time_Office,
T.Days,
Distinct_office_locations = count(distinct V.Office)
from view_1 V
Cross apply
(
Select top 1 Id,
Max_Time_Office = Office,
Days = sum(Days)
From view_1 VG
where V.Id = VG.Id
group by VG.Id, VG.Office
order by sum(Days) desc
) T
group by V.Id, T.Max_Time_Office, T.Days
Basically, you are getting the Office with most days in the order by sum(Days) desc inside the Cross apply, and using that in the outer expression. I then just did a count(distinct V.Office) to get the distinct offices.