Вы можете использовать функцию окна SUM:
Тестовые данные:
declare @t table (Column1 varchar(10), Column2 varchar(10), Column3 varchar(10), Column4 int)
insert into @t values
('Col1Data0','Test1','Test2',1),
('Col1Data0','Test1','Test2',3),
('Col1Data1','Test1','Test2',2),
('Col1Data1','Test1','Test2',5)
Запрос:
SELECT Column1, Column2, Column3,
SUM(Column4) OVER (PARTITION BY Column1) AS SumColumn4
FROM @t
Возвраты:
Column1 Column2 Column3 SumColumn4
Col1Data0 Test1 Test2 4
Col1Data0 Test1 Test2 4
Col1Data1 Test1 Test2 7
Col1Data1 Test1 Test2 7