How to get Data in this way

/*Soution 1: As wanted*/
WITH [Collection]
AS
(
	SELECT ROW_NUMBER() OVER(ORDER BY UID) AS RowId, Coll.*
		FROM Table2 AS Coll
),
LastCollection
AS
(
	SELECT MAX(RowId)AS RowId, UID AS LastId
		FROM [Collection]
		GROUP BY UID
)
SELECT 
	Bill.*,
	Coll.[Collection] AS Coll,
	CASE
		WHEN(LastColl.RowId IS NULL) THEN(SELECT 0)
		ELSE(
			-- total bill - (sum of previous collections and current row collection)
			COALESCE(Bill.Bill, 0) - COALESCE((SELECT SUM(PreColl.Collection)
													FROM [Collection] AS PreColl
													WHERE PreColl.UID = Coll.UID 
														AND PreColl.RowId <= Coll.RowId), 0)
		)
	END AS Outstd
	FROM Table1 AS Bill
	INNER JOIN [Collection] AS Coll ON Bill.UID = Coll.UID
	LEFT JOIN LastCollection AS LastColl ON Coll.RowId = LastColl.RowId;

/*Soution 2: improved*/
WITH [Collection]
AS
(
	SELECT ROW_NUMBER() OVER(ORDER BY UID) AS RowId, Coll.*
		FROM Table2 AS Coll
)
SELECT Bill.*, Coll.Collection AS Coll,
	-- total bill - (sum of previous collections and current row collection)
	COALESCE(Bill.Bill, 0) - COALESCE((SELECT SUM(PreColl.Collection)
											FROM [Collection] AS PreColl
											WHERE PreColl.UID = Coll.UID 
												AND PreColl.RowId <= Coll.RowId), 0)AS Outstd
	FROM Table1 AS Bill
	INNER JOIN [Collection] AS Coll ON Bill.UID = Coll.UID;

/*Soution 3: I like it*/
SELECT AllUser.UID,
	COALESCE(TtlBill.Bill, 0) AS Bill,
	COALESCE(TtlCollection.Coll, 0) AS Coll,
	COALESCE(TtlBill.Bill, 0) - COALESCE(TtlCollection.Coll, 0) AS Outstd
	--total usser
	FROM(
		SELECT *
			FROM(
				SELECT UID FROM Table1
				UNION ALL
				SELECT UID FROM Table2
			) AS Users
			GROUP BY UID
	) AS AllUser
	
	--total Bill
	LEFT JOIN(
		SELECT UID, SUM(Bill) AS Bill
			FROM Table1
			GROUP BY UID
	) AS TtlBill
	ON AllUser.UID = TtlBill.UID
	
	--total Collection
	LEFT JOIN(
	SELECT UID, SUM(Collection) AS Coll
		FROM Table2
		GROUP BY UID
	) AS TtlCollection
	ON AllUser.UID = TtlCollection.UID;

select *, OutStd --(put ur logic here) 
from tbl1
left outer join tbl2 on tbl.UID =UID