-- 1. Outer Join & Null Check
SELECT b.*
  FROM a, b
 WHERE a.p1(+) = b.p1
   AND a.p2(+) = b.p2
   AND a.p3(+) = b.p3
   AND a.p1 IS NULL
;

-- 2. Not Exists
SELECT * FROM b
 WHERE NOT EXISTS (SELECT * FROM a
                    WHERE a.p1 = b.p1
                      AND a.p2 = b.p2
                      AND a.p3 = b.p3
                   )
;

-- 3. Not In
SELECT * FROM b
 WHERE (p1, p2, p3) NOT IN (SELECT p1, p2, p3 FROM a)
;

-- 4. Merge Into
MERGE INTO a
USING b
ON (a.p1 = b.p1
AND a.p2 = b.p2
AND a.p3 = b.p3)
WHEN NOT MATCHED THEN
INSERT
VALUES(b.p1, b.p2, b.p3, ...)
;

마농님 답변 주셔서 고맙습니다.