with t1 as
(
     select 'A110' c1,date'2012-09-28' c2 from dual
     union all
     select 'A100' c1,date'2012-07-09' c2 from dual
     union all
     select 'A110' c1,date'2012-10-01' c2 from dual
     union all
     select 'A110' c1,date'2012-10-01' c2 from dual
     union all
     select 'A110' c1,date'2012-10-03' c2 from dual
     union all
     select 'A110' c1,date'2012-10-05' c2 from dual
     union all
     select 'A120' c1,date'2012-10-01' c2 from dual
     union all
     select 'A000' c1,date'2012-10-03' c2 from dual
)
select c.c1,c.t_date,count(d.c2) c_num
from 
(
select a.c1,b.t_date
from 
  (
    select distinct c1
    from t1
    where c2 between trunc(date'2012-10-03','month') and date'2012-10-03'
  ) a,
  (
    select trunc(date'2012-10-03','month')+level-1 t_date
    from dual
    connect by level <= date'2012-10-03'-trunc(date'2012-10-03','month')+1
  ) b
) c left join t1 d on c.c1 = d.c1 and c.t_date = d.c2
group by c.c1,c.t_date
order by c.c1,c.t_date

     c1      t_date     c_num
--------------------------------------
1    A000    2012/10/1    0
2    A000    2012/10/2    0
3    A000    2012/10/3    1
4    A110    2012/10/1    2
5    A110    2012/10/2    0
6    A110    2012/10/3    1
7    A120    2012/10/1    1
8    A120    2012/10/2    0
9    A120    2012/10/3    0

------解决方案--------------------

[code=SQL][/code]
with t1 as
(   
    select 'A000' c1,date'2012-10-03' c2,1 c3 from dual
    union all
    select 'A100' c1,date'2012-07-09' c2,2 c3 from dual
    union all   
    select 'A100' c1,date'2012-10-01' c2,3 c3 from dual
    union all  
    select 'A100' c1,date'2012-10-03' c2,4 c3 from dual
    union all  
    select 'A100' c1,date'2012-10-05' c2,5 c3 from dual
    union all     
    select 'A110' c1,date'2012-08-09' c2,6 c3 from dual
    union all   
    select 'A110' c1,date'2012-10-01' c2,7 c3 from dual
    union all  
    select 'A110' c1,date'2012-10-02' c2,8 c3 from dual
    union all  
    select 'A110' c1,date'2012-10-04' c2,9 c3 from dual
    union all   
    select 'A120' c1,date'2012-10-01' c2,5 c3 from dual
    union all   
    select 'A120' c1,date'2012-10-02' c2,7 c3 from dual
    union all  
    select 'A120' c1,date'2012-10-03' c2,3 c3 from dual
)
select t4.c1,t4.c2,nvl(t1.c3,0) from t1,
 (select * from
   (select distinct c1 from t1)t2,
   (select date'2012-10-06' + 1 - level c2 from dual connect by level <= to_number(to_char(date'2012-10-06','dd')))t3
 )t4  
where t1.c1(+) = t4.c1 and t1.c2(+) = t4.c2

1	A000	2012/10/1	0
2	A000	2012/10/2	0
3	A000	2012/10/3	1
4	A000	2012/10/4	0
5	A000	2012/10/5	0
6	A000	2012/10/6	0
7	A100	2012/10/1	3
8	A100	2012/10/2	0
9	A100	2012/10/3	4
10	A100	2012/10/4	0
11	A100	20