WITH t AS
(
SELECT 1 gb, 'A' cd, 1 no, 'N' yn, null v FROM dual
UNION ALL SELECT 1, 'B', 2, 'Y',   20 FROM dual
UNION ALL SELECT 1, 'B', 3, 'Y',   20 FROM dual
UNION ALL SELECT 2, 'A', 1, 'Y',   20 FROM dual
UNION ALL SELECT 2, 'B', 2, 'Y',   20 FROM dual
UNION ALL SELECT 2, 'B', 3, 'Y',   20 FROM dual
UNION ALL SELECT 3, 'A', 1, 'N', null FROM dual
UNION ALL SELECT 3, 'B', 2, 'Y',   20 FROM dual
UNION ALL SELECT 3, 'B', 3, 'N', null FROM dual
UNION ALL SELECT 4, 'A', 1, 'N', null FROM dual
UNION ALL SELECT 4, 'B', 2, 'N', null FROM dual
UNION ALL SELECT 4, 'B', 3, 'Y',   20 FROM dual
UNION ALL SELECT 5, 'A', 1, 'Y',   20 FROM dual
UNION ALL SELECT 5, 'B', 2, 'Y',   20 FROM dual
UNION ALL SELECT 5, 'B', 3, 'N', null FROM dual
UNION ALL SELECT 6, 'A', 1, 'Y',   20 FROM dual
UNION ALL SELECT 6, 'B', 2, 'N', null FROM dual
UNION ALL SELECT 6, 'B', 3, 'N', null FROM dual
)
SELECT cd, no, yn
     , CASE WHEN yn = 'Y'
             AND ROW_NUMBER() OVER(PARTITION BY yn ORDER BY no) = 1
            THEN v END v
  FROM t
 WHERE gb = 1  -- 유형별 조건
 ORDER BY no
;

마농님 감사합니다. 좋은 하루보내세요 ^^;