N
Size: a a a
AS
DN
NB
NB
DN
DN
select top 1 with ties username, id, sumhttps://dbfiddle.uk/?rdbms=sqlserver_2019&fiddle=2add0516a3f34a440ee66da6ff07f894
from users
group by username, id, sum
order by row_number () over (partition by username order by [sum] desc)
NB
F
L
АК
DN
user4
MS
РR
DN