재귀 쿼리로 풀어봤습니다.

합쳐서 일자별로 번호하나 매기고

1번부터 시작해서

2번은 1번과 합하고

다시 3번은 계산된 2번과 합하고

....(반복)

;with aTable AS

(

       SELECT 1 AS seq, CONVERT(DATETIME, '2013-12-01') AS accdate, 10000 AS Dr, 0 AS Cr

       UNION ALL

       SELECT 2, '2013-12-10', 20000, 0

       UNION ALL

       SELECT 3, '2013-12-20', 30000, 0

       UNION ALL

       SELECT 4, '2013-12-26', 50000, 0

), bTable AS

(

       SELECT 1 AS seq, CONVERT(DATETIME, '2013-12-05') AS accdate, 0 AS Dr, 10000 AS Cr

       UNION ALL

       SELECT 2, '2013-12-15', 0, 20000

), UniTable AS

(

       SELECT ROW_NUMBER() OVER (ORDER BY accdate) AS NUM, *

       FROM

       (

             SELECT * FROM aTable

             UNION ALL

             SELECT * FROM bTable

       ) AS A

), SumTable AS

(

       SELECT Num, Accdate, Dr, Cr, Dr-Cr as total

       FROM UniTable

       WHERE NUM=1

       UNION ALL

       SELECT B.Num, B.Accdate, B.Dr, B.Cr, A.total + (B.Dr-B.Cr) as total

       FROM SumTable AS A

       JOIN UniTable AS B

       ON A.NUM+1=B.NUM

)

SELECT * FROM SumTable

ORDER BY NUM