WITH t AS
(
SELECT 1 seq, 1 cnum FROM dual
UNION ALL SELECT  2, 2 FROM dual
UNION ALL SELECT  3, 1 FROM dual
UNION ALL SELECT  4, 2 FROM dual
UNION ALL SELECT  5, 3 FROM dual
UNION ALL SELECT  6, 4 FROM dual
UNION ALL SELECT  7, 1 FROM dual
UNION ALL SELECT  8, 2 FROM dual
UNION ALL SELECT  9, 3 FROM dual
UNION ALL SELECT 10, 1 FROM dual
UNION ALL SELECT 11, 2 FROM dual
UNION ALL SELECT 12, 3 FROM dual
UNION ALL SELECT 13, 4 FROM dual
UNION ALL SELECT 14, 5 FROM dual
)
SELECT seq, cnum
     , COUNT(*) OVER(PARTITION BY grp) cnt
  FROM (SELECT seq, cnum
             , COUNT(DECODE(cnum, 1, 1)) OVER(ORDER BY seq) grp
          FROM t
        )
;

빠른 답변 감사드립니다.

덕분에 잘 해결 될 거 같습니다. ^^