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Question

I'm using SQL Server 2016 and I have a table with the following records:
Create table MemberCount
(
ssn char(9) null,
extract_begin_dt smalldatetime null,
extract_end_dt smalldatetime null,
memberCase varchar(13) null
)
insert into MemberCount(ssn, extract_begin_dt, extract_end_dt, memberCase)
values (1, '1/1/2017', '1/31/2017', 'Non-Funded'),
(1, '2/1/2017', '12/31/2017', 'OpenAccts'),
(2, '1/1/2017', '3/31/2017', 'OpenAccts'),
(2, '4/1/2017', '12/31/2017', 'OpenAccts'),
(3, '1/1/2014', '3/31/2014', 'OpenAccts'),
(3, '4/1/2014', '10/31/2017', 'ClosedAccts'),
(3, '11/1/2017', '12/31/2017', 'OpenAccts'),
(7, '9/19/2017', '12/31/2017', 'OpenAccts'),
(7, '9/15/2017', '9/18/2017', 'OpenAccts'),
(7, '8/26/2017', '9/14/2017', 'OpenAccts'),
(7, '4/9/2015', '8/25/2017', 'OpenAccts'),
(7, '4/8/2015', '4/8/2015', 'OpenAccts'),
(7, '4/7/2015', '4/7/2015', 'ClosedAccts'),
(7, '1/1/2015', '4/6/2015', 'OpenAccts'),
(7, '5/22/2014', '12/31/2014', 'OpenAccts'),
(7, '8/21/2013', '5/21/2014', 'OpenAccts'),
(7, '6/20/2013', '8/20/2013', 'Non-Funded'),
(7, '4/20/2013', '6/19/2013', 'Non-Funded'),
(7, '1/12/2011', '1/12/2011', 'DeletedAccts'),
(7, '12/31/2010', '1/11/2011', 'OpenAccts')
The expected result
ssn begin_dt
----------------
1 2/1/2017
2 1/1/2017
3 11/1/2017
7 12/31/2017
The rules are if there is no memberCase other then OpenAccount the min date will be chosen, if there other then OpenAccount it will go until the open account will be the current one
I've tried with windows function but number 2 and 3 are opposite logic
Thanks,
Oded Dror

Answer 1

Check this query. But result is a bit different from your provided result. For ssn=7 you expect 12/31/2017. But it is extract_end_dt. Are not you getting extract_begin_dt?
select
ssn, extract_begin_dt
from (
select
*, mc1 = min(memberCase) over (partition by ssn), mc2 = max(memberCase) over (partition by ssn)
, dt1 = min(extract_begin_dt) over (partition by ssn), dt2 = max(extract_begin_dt) over (partition by ssn)
from
MemberCount
) t
where
1 = case
when mc1 = mc2 and mc1 = 'OpenAccts' and dt1 = extract_begin_dt then 1
when mc1 <> mc2 and dt2 = extract_begin_dt then 1
else 0
end
Result
ssn extract_begin_dt
1 2017-02-01 00:00:00
2 2017-01-01 00:00:00
3 2017-11-01 00:00:00
7 2017-09-19 00:00:00
Edit: updated query according to your comment
select
ssn, begin_dt = max(begin_dt)
from (
select
ssn, grp, begin_dt = min(extract_begin_dt)
from (
select
*, grp = rn - row_number() over (partition by ssn order by extract_begin_dt)
from (
select
*, rn = row_number() over (partition by ssn order by extract_begin_dt)
from
MemberCount
) t
where
memberCase = 'OpenAccts'
) t
group by ssn, grp
) t
group by ssn