select to_date('2011'||lpad(2,2,'0'),'YYYYMM')+rownum-1 from dual 
connect by rownum<=(select to_date('2011'||lpad(2+1,2,'0'),'YYYYMM')-to_date('2011'||lpad(2,2,'0'),'YYYYMM') from dual)

------解决方案--------------------

SQL code

--根据年月获取起始日期
select max(sdate) m_date,min(sdate) n_date from (
select to_char(to_date('2011'||'-01', 'YYYY-MM') + rownum - 1, 'YYYY-MM-DD') as sdate 
from dual
connect by rownum <= 365)
where to_char(to_date(sdate,'yyyy-mm-dd'),'MM')=2

         m_date           n_date
-----------------------------------
1    2011-02-28    2011-02-01


--根据年和季度获取起始日期
select max(sdate) m_date,min(sdate) n_date from (
select to_char(to_date('2011'||'-01', 'YYYY-MM') + rownum - 1, 'YYYY-MM-DD') as sdate 
from dual
connect by rownum <= 365)
where to_char(to_date(sdate,'yyyy-mm-dd'),'Q')=3

         m_date           n_date
-----------------------------------
1    2011-09-30    2011-07-01