Adding an aggregate column causing GROUP BY error - sql

Question

I'm adding an aggregate column min(finumber) to my query. Once I add this number I want to be able to use it in the ORDER BY. When I remove the min(finumber) the query works fine. When I add min(finumber) it gives me the error:
Column 'soitem.fsono' is invalid in the select list because it is not
contained in either an aggregate function or the GROUP BY clause.
My question is: How am I able to add min(finumber) and use it to ORDER BY my data?
SELECT A.fsono,
MAX(A.Attention) AS Attention,
MAX(A.Address1) AS Address1,
MAX(A.Address2) AS Address2,
A.fcustno,
A.fcontact,
A.min_fin
FROM (SELECT soitem.fsono,
somast.fcustno,
somast.fcontact,
min(finumber)as min_fin,
CASE
WHEN (CONVERT(varchar(MAX), soship.fmstreet)) LIKE 'ATTN%' THEN LEFT(CONVERT(varchar(MAX), soship.fmstreet), CHARINDEX(CHAR(10), CONVERT(varchar(MAX), soship.fmstreet)))
ELSE NULL
END AS Attention,
CASE WHEN [id] = 2 THEN S.val ELSE NULL END AS Address1,
CASE WHEN [id] = 3 THEN S.val ELSE NULL END AS Address2
FROM soitem
INNER JOIN somast ON soitem.fsono = somast.fsono
LEFT OUTER JOIN soship ON somast.fsono = soship.fcsono
AND soship.fcenumber = ''
CROSS APPLY [dbo].[split3](soship.fmstreet, CHAR(13) + CHAR(10)) S
WHERE (somast.fstatus <> 'Cancelled')
AND (somast.fsocoord = 'IFP'
OR somast.fsocoord = '711')
AND somast.fsono >= '034023') A
GROUP BY A.fsono,
A.fcustno,
A.fcontact
Order by A.fsono, A.min_fin
;

Answer 1

The error is telling you the problem here.
min(finumber) is in your subquery, not your main query. Your sub query doesn't have a GROUP BY, hence the error. You'll need to use an OVER clause. This is pseudo SQL, however:
MIN(finumber) OVER (PARTITION BY {Partition Columns}) AS min_fin
I would guess those columns would be soitem.fsono, somast.fcustno, somast.fcontact.