t sql Group By clause not having intended effect - sql-server

Question

I am having some trouble with what I believe is a group by clause. I am trying to display a distinct CompanyID with the earliest InstallDate
Here is my code:
SELECT
Pa.PARTY_ID
,MIN(SM.[INSTALLDATE]) INSTALLDATE
,SM.[STOPDATE]
FROM FORMDESC FD
INNER JOIN STATEINFO SI
ON FD.FORMDESCID = SI.FORMDESCID
INNER JOIN COMPANY C
ON FD.COMPANYID = C.COMPANYID
INNER JOIN PARTY Pa
ON C.COMPANYFULLNAME = Pa.FULL_NM
INNER JOIN STATEMARKET SM
ON SI.STATEINFOID = SM.STATEINFOID
WHERE ENTIREFORMNUMBER = 'ABC123'
GROUP BY PARTY_ID, INSTALLDATE, STOPDATE
My current output is:
CompanyID | INSTALLDATE | STOPDATE
-------------------------------------------
60 | NULL | NULL
61 | 2015-09-26 00:00:00 | NULL
62 | NULL | NULL
62 | 2014-09-29 00:00:00 | NULL
62 | 2016-04-15 00:00:00 | NULL
The output I am seeking is:
CompanyID | INSTALLDATE | STOPDATE
----------------------------------------
60 | NULL | NULL
61 | 2015-09-26 00:00:00 | NULL
62 | 2014-09-29 00:00:00 | NULL
A left join on the SM table will not help me here either. If I pull any of the values from my group by clause, I get an error.
Is this a case where I should break this into a couple of selects instead?
While James Z's answer would indeed work; it was pointed out to me that my group by contained INSTALLDATE which caused my issue.

Answer 1

You probably need something like this:
select * from (
SELECT
Pa.PARTY_ID
,SM.[INSTALLDATE]
,SM.[STOPDATE]
,row_number() over (partition by Pa.PARTY_ID order by SM.[INSTALLDATE] desc) as RN
FROM FORMDESC FD
INNER JOIN STATEINFO SI
ON FD.FORMDESCID = SI.FORMDESCID
INNER JOIN COMPANY C
ON FD.COMPANYID = C.COMPANYID
INNER JOIN PARTY Pa
ON C.COMPANYFULLNAME = Pa.FULL_NM
INNER JOIN STATEMARKET SM
ON SI.STATEINFOID = SM.STATEINFOID
WHERE ENTIREFORMNUMBER = 'ABC123'
) X
where RN = 1
This will number the rows separately for each party_id, and then show the earliest one of them. This way you can get other data from the same row where the minimum value exists.