-- Prepare sample data to mimic your environment
DECLARE	@Tb1 TABLE (StationID INT, Day INT, No_In INT)

INSERT	@Tb1
SELECT	1, 2, 90 UNION ALL
SELECT	1, 5, 80 UNION ALL
SELECT	1, 4, 10

DECLARE	@Tb2 TABLE (StationID INT, Day INT, No_Out INT)

INSERT	@Tb2
SELECT	1, 2, 70 UNION ALL
SELECT	1, 1, 10 UNION ALL
SELECT	1, 3, 90 UNION ALL
SELECT	1, 5, 60

-- Show the expected output
SELECT		d.StationID,
		d.Day,
		SUM(d.No_In) AS No_In,
		SUM(d.No_Out) AS No_Out
FROM		(
			SELECT	StationID,
				Day,
				No_In,
				0 AS No_Out
			FROM	@Tb1

			UNION ALL

			SELECT	StationID,
				Day,
				0,
				No_Out
			FROM	@Tb2
		) AS d
GROUP BY	d.StationID,
		d.Day
ORDER BY	d.StationID,
		d.Day

CREATE VIEW dbo.vwTb3
AS

SELECT		d.StationID,
		d.Day,
		SUM(d.No_In) AS No_In,
		SUM(d.No_Out) AS No_Out
FROM		(
			SELECT	StationID,
				Day,
				No_In,
				0 AS No_Out
			FROM	Tb1

			UNION ALL

			SELECT	StationID,
				Day,
				0,
				No_Out
			FROM	Tb2
		) AS d
GROUP BY	d.StationID,
		d.Day