아래처럼 표현 가능합니다.(11g r2이상)

 
set pages 100
col jan_names format a5
col feb_names format a5
col mar_names format a5
col apr_names format a5
col may_names format a5
col jun_names format a5
col jul_names format a5
col aug_names format a5
col sep_names format a5
col oct_names format a5
col nov_names format a5
col dec_names format a5

with data as
(
  select 'A' as name, to_date('2015-05-01', 'yyyy-mm-dd') d from dual union all
  select 'B' as name, to_date('2015-05-01', 'yyyy-mm-dd') d from dual union all
  select 'C' as name, to_date('2015-08-25', 'yyyy-mm-dd') d from dual union all
  select 'D' as name, to_date('2015-11-02', 'yyyy-mm-dd') d from dual  
)
,
days
as
( 
  select level d from dual connect by level < 32
)
select * from 
(
	select 
		days.d day, data2.month, data2.name
	from 
	days
	left join
	(
	  select extract(month from d) month , extract(day from d) d, name
	  from data 
	) data2 on days.d = data2.d
) x
pivot 
(
	 listagg(name, ',') within group (order by name) as names
	 for ( month ) in ( 1 as jan,2 as feb,3 as mar,4 as apr,5 as may,6 as jun,7 as jul,8 as aug,9 as sep,10 as oct,11 as nov,12 as dec)
)
order by 1
/
 
 
       DAY JAN_N FEB_N MAR_N APR_N MAY_N JUN_N JUL_N AUG_N SEP_N OCT_N NOV_N DEC_N 
---------- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- -----
	 1			   A,B
	 2							       D
	 3
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	25					     C
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