SQL code
with a as(
select '张三' xm,to_date('2012-04-01','yyyy-mm-dd') ksrq,to_date('2012-04-03','yyyy-mm-dd') jsrq from dual
union all
select '李四',to_date('2012-04-01','yyyy-mm-dd'),to_date('2012-04-02','yyyy-mm-dd') from dual
union all
select '王五',to_date('2012-04-05','yyyy-mm-dd'),to_date('2012-04-06','yyyy-mm-dd') from dual
)
select count(1), ksrq + rn - 1
  from a,
       (select rownum rn
          from dual
        connect by rownum <= (select max(jsrq - ksrq) from a)) t
 where a.jsrq >= a.ksrq + rn - 1
 group by ksrq + rn - 1
  COUNT(1) KSRQ+RN-1
---------- -----------
         2 2012-4-1
         2 2012-4-2
         1 2012-4-3
         1 2012-4-5
         1 2012-4-6

------解决方案--------------------

SQL code

with a as(
select '张三' xm,to_date('2012-04-01','yyyy-mm-dd') b_date,to_date('2012-04-03','yyyy-mm-dd') e_date from dual
union all
select '李四',to_date('2012-04-01','yyyy-mm-dd'),to_date('2012-04-02','yyyy-mm-dd') from dual
union all
select '王五',to_date('2012-04-05','yyyy-mm-dd'),to_date('2012-04-06','yyyy-mm-dd') from dual
)


select count(1) 总人数,d_date 日期
from a,
(select date'2012-04-01'+level-1 d_date
from dual
connect by level <= 30) b
where b.d_date <= a.e_date and b.d_date >= a.b_date
group by d_date
order by d_date

   总人数   日期
---------------------------------
1    2    2012/4/1
2    2    2012/4/2
3    1    2012/4/3
4    1    2012/4/5
5    1    2012/4/6