Попробуйте это:
DECLARE @DataSource TABLE
(
[Date] DATE
,[InQty] INT
,[OutQty] INT
);
INSERT INTO @DataSource ([Date], [InQty], [OutQty])
VALUES ('20180901', 1000, 200)
,('20180902', 0, 300)
,('20180903', 1000, 100);
SELECT *
,SUM([InQty]-[OutQty]) OVER (ORDER BY [Date])
FROM @DataSource
ORDER BY [Date];
