-- 1. Full Outer Join --
SELECT NVL(a.eno, b.eno) eno
     , a.mno mno_a
     , b.mno mno_b
  FROM a
  FULL OUTER JOIN b
    ON a.eno = b.eno
   AND a.mno = b.mno
 ORDER BY eno, mno_a, mno_b
;

-- 2. Union & Group By --
SELECT eno
     , MIN(mno_a) mno_a
     , MIN(mno_b) mno_b
  FROM (SELECT eno, mno, mno  mno_a, null mno_b FROM a
         UNION ALL
        SELECT eno, mno, Null mno_a, mno  mno_b FROM b
        )
 GROUP BY eno, mno
 ORDER BY eno, mno_a, mno_b
;

완전 감사합니다.~~

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