[SYS@myorcl] SQL>WITH T1 AS
  2   (SELECT '0001' AAC001, DATE '2011-06-25' ALC034
  3      FROM DUAL
  4    UNION
  5    SELECT '0002' AAC001, DATE '2011-05-25' ALC034 FROM DUAL)
  6  SELECT AAC001, COLUMN_VALUE
  7    FROM T1,
  8         TABLE(CAST(MULTISET
  9                    (SELECT TO_CHAR(ADD_MONTHS(TRUNC(ALC034, 'mm'), LEVEL),
 10                                    'yyyy-mm')
 11                       FROM DUAL
 12                     CONNECT BY LEVEL <=
 13                                MONTHS_BETWEEN(TRUNC(SYSDATE, 'mm'),
 14                                               TRUNC(ALC034, 'MM'))) AS
 15                    SYS.ODCIVARCHAR2LIST));

AAC0 COLUMN_VALUE
---- --------------------
0001 2011-07
0001 2011-08
0002 2011-06
0002 2011-07
0002 2011-08

[SYS@myorcl] SQL>