이런걸 원하신건지..

아래쿼리는 대량이면 속도는 느려질수 있습니다.

WITH MAST AS
(
 SELECT '2012-01-01' DT, 'A1' CD FROM DUAL UNION ALL
 SELECT '2012-01-02' DT, 'A1' CD FROM DUAL UNION ALL
-- SELECT '2012-01-03' DT, 'A1' CD FROM DUAL UNION ALL
 SELECT '2012-01-04' DT, 'A1' CD FROM DUAL UNION ALL
 SELECT '2012-01-05' DT, 'A1' CD FROM DUAL UNION ALL
 SELECT '2012-01-06' DT, 'A1' CD FROM DUAL UNION ALL
 SELECT '2012-05-05' DT, 'A1' CD FROM DUAL UNION ALL
 SELECT '2012-05-06' DT, 'A1' CD FROM DUAL
), HIST AS
(
 SELECT '2012-01-01' DT,  'A1' CD, 'PPP' TYPE FROM DUAL UNION ALL
 SELECT '2012-01-03' DT,  'A1' CD, 'QQQ' TYPE FROM DUAL UNION ALL
 SELECT '2012-01-06' DT,  'A1' CD, 'ZZZ' TYPE FROM DUAL
)
SELECT  M.DT
       ,M.CD
       ,(SELECT SUBSTR(MAX(DT||TYPE),11) TYPE FROM HIST H WHERE M.CD = H.CD AND M.DT >= H.DT)
FROM   MAST M