WITH T AS
(   
SELECT 'A' 구분,'경기#경기#전남#서울' TEXT FROM DUAL UNION ALL
SELECT 'B' 구분,'경기#경기'           TEXT FROM DUAL UNION ALL
SELECT 'C' 구분,'경기#경기#인천#광주' TEXT FROM DUAL UNION ALL
SELECT 'D' 구분,'경기#전남#전남'      TEXT FROM DUAL UNION ALL
SELECT 'E' 구분,'경기#강원#울산#서울#광주#인천' TEXT FROM DUAL UNION ALL
SELECT 'F' 구분,'인천' TEXT FROM DUAL
)                     
SELECT 구분, REGEXP_REPLACE(TEXT,'([^#]+)(#\1)+','\1') TEXT FROM T

오..감사합니다.^^

근데 한가지 제가 놓친 케이스가 있네요.ㅠㅠ

SELECT 'C' 구분,'경기#경기#인천#광주#경기' TEXT FROM DUAL 

"경기"가 연속해서 안올수도 있습니다.

WITH t AS
(
SELECT 'A' 구분, '경기#경기#전남#서울' text FROM dual
UNION ALL SELECT 'B', '경기#경기'                     FROM dual
UNION ALL SELECT 'C', '경기#경기#인천#광주'           FROM dual
UNION ALL SELECT 'D', '경기#전남#전남'                FROM dual
UNION ALL SELECT 'E', '경기#강원#울산#서울#광주#인천' FROM dual
UNION ALL SELECT 'F', '인천'                          FROM dual
UNION ALL SELECT 'G', '경기#경기#인천#광주#경기'      FROM dual
)
SELECT 구분
     , LISTAGG(text, '#') WITHIN GROUP(ORDER BY lv) text
  FROM (SELECT 구분
             , REGEXP_SUBSTR(text, '[^#]+', 1, lv) text
             , MIN(lv) lv
          FROM t
             , (SELECT LEVEL lv FROM dual CONNECT BY LEVEL <= 9)
         WHERE lv <= REGEXP_COUNT(text, '[^#]+')
         GROUP BY 구분
             , REGEXP_SUBSTR(text, '[^#]+', 1, lv)
        )
 GROUP BY 구분
 ORDER BY 구분
;