Код:

SELECT A.point, 
CASE A.sum1 WHEN NULL THEN 0 ELSE A.sum1 END -
CASE A.sum2 WHEN NULL THEN 0 ELSE A.sum2 END FROM (
SELECT A.point, B.sum sum1, C.sum sum2 FROM 
(
SELECT A.point FROM (
SELECT Inc.point FROM Income_o Inc
WHERE '20010415' > date  GROUP BY point) AS A
UNION
SELECT A.point FROM (
SELECT Out.point FROM Outcome_o Out
WHERE '20010415' > date GROUP BY point
) AS A
) AS A
LEFT JOIN
(SELECT Inc.point, 
CASE SUM(Inc.inc) WHEN NULL THEN 0 ELSE SUM(Inc.inc) END  sum FROM Income_o Inc
 WHERE '20010415' > date  GROUP BY point
) AS B
ON A.point = B.point
LEFT JOIN
(
SELECT Out.point, 
CASE SUM(Out.out) WHEN NULL THEN 0 ELSE SUM(Out.out) END sum FROM Outcome_o Out
WHERE '20010415' > date GROUP BY point
) AS C
ON
A.point = C.point
) AS A