WITH t AS
(
SELECT '20130101' frdt, '20131231' todt, 1000 amt FROM dual
UNION ALL SELECT '20130520', '20140228', 2000 FROM dual
UNION ALL SELECT '20130412', '20140131',  500 FROM dual
)
SELECT frdt, todt, amt
  FROM (SELECT TO_CHAR(dt, 'yyyymmdd') frdt
             , TO_CHAR(LEAD(dt) OVER(ORDER BY dt) - 1, 'yyyymmdd') todt
             , SUM(SUM(amt)) OVER(ORDER BY dt) amt
          FROM (SELECT DECODE(lv, 1, TO_DATE(frdt, 'yyyymmdd')
                                , 2, TO_DATE(todt, 'yyyymmdd') + 1
                                ) dt
                     , DECODE(lv, 1, amt, -amt) amt
                  FROM t
                     , (SELECT LEVEL lv FROM dual CONNECT BY LEVEL <= 2)
                )
         GROUP BY dt
        )
 WHERE amt > 0
;

WITH T AS(
SELECT '20130101' FRDT,  '20131231' TODT, 1000 AMT FROM DUAL UNION ALL
SELECT '20130520',       '20140228',      2000     FROM DUAL UNION ALL
SELECT '20130412',       '20140131',       500     FROM DUAL
)
SELECT MIN(X.TARGET_DATE) AS START_DATE
     , MAX(X.TARGET_DATE) AS END_DATE
     , X.AMT
  FROM (SELECT T1.TARGET_DATE
             , SUM(T2.AMT) AS AMT
          FROM (SELECT FROMDATE + (LEVEL -1) AS TARGET_DATE
                  FROM (SELECT MIN(TO_DATE(FRDT, 'YYYYMMDD')) AS FROMDATE
                             , MAX(TO_DATE(TODT, 'YYYYMMDD')) AS TODATE
                          FROM T
                        ) X
                CONNECT BY LEVEL <= X.TODATE - X.FROMDATE
               ) T1
               LEFT OUTER JOIN T T2
               ON  T1.TARGET_DATE BETWEEN TO_DATE(FRDT,'YYYYMMDD')
                                      AND TO_DATE(TODT,'YYYYMMDD')
         GROUP BY T1.TARGET_DATE
       ) X
 GROUP BY X.AMT
 ORDER BY MIN(X.TARGET_DATE)

마농님과 팡님의 도움에

진심으로 감사드립니다. ^^

팡님의 쿼리엔 오류가...

예시 결과 5개행의 금액이 모두 달라서. 우연하게 결과만 맞게 나온 것이죠.

원본 자료에 20140210, 20140220, 500 을 추가해 보면...

그러네요;;

단순히 날짜별로 데이터 생성해서 AMT로 GROUP BY 쳐버렸는데

데이터가 추가되면 잘못 나오겠네요 ㅠㅠ