이게 맞으려나요...
select
id_pc,
to_char(visit_time, 'yyyy/mm/dd') as day_num,
to_char(visit_time, 'dy') as date_char,
count(id_pc) over(partition by to_char(visit_time, 'iw')) cnt
from (
select
id_pc, visit_time
row_number() over(partition by visit_time, id_pc order by visit_time) rnk
from ci_visitor_info
where visit_time >= to_date('2014/01/01', 'yyyy/mm/dd')
and to_date('2014/02/15', 'yyyy/mm/dd') + 1>visit_time 
and id_site = 2
) a
where rnk=1
order by visit_time
;

row_number() over(partition by visit_time, id_pc order by visit_time) rnk
rnk가 모두 1이되어서 데이터 분기를 제대로 못하네요 ㅠ ㅠ

제 핵심은 주간으로...조회하는것입니다  ㅠ ㅠ

그래도 도움주셔서 감사합니다^^

WITH t (ID_PC , DAY_NUM , DATE_CHAR)AS (
SELECT '1','14/01/01','수'FROM DUAL UNION ALL
SELECT '2','14/01/01','수'FROM DUAL UNION ALL
SELECT '3','14/01/03','금'FROM DUAL UNION ALL
SELECT '1','14/01/05','일'FROM DUAL UNION ALL
SELECT '2','14/01/07','화'FROM DUAL UNION ALL
SELECT '2','14/01/10','금'FROM DUAL UNION ALL
SELECT '4','14/01/10','금'FROM DUAL UNION ALL
SELECT '5','14/01/13','월'FROM DUAL UNION ALL
SELECT '7','14/01/14','화'FROM DUAL UNION ALL
SELECT '1','14/01/18','토'FROM DUAL UNION ALL
SELECT '2','14/01/19','일'FROM DUAL UNION ALL
SELECT '2','14/01/19','일'FROM DUAL UNION ALL
SELECT '2','14/01/27','월'FROM DUAL UNION ALL
SELECT '1','14/02/01','토'FROM DUAL UNION ALL
SELECT '1','14/02/01','토'FROM DUAL UNION ALL
SELECT '4','14/02/03','월'FROM DUAL
)
SELECT t.id_pc
     , t.day_num
     , t.date_char
     , count(*) over ( partition by iw ) cnt
  FROM (
          SELECT t.*
               , row_number() over ( partition by case when date_char = '일' 
                                                       then trunc ( to_date ( day_num, 'rrrr/mm/dd' ) - 1, 'iw' ) 
                                                       else trunc ( to_date ( day_num, 'rrrr/mm/dd' ), 'iw' )
                                                   end 
                                                , id_pc 
                                         order by day_num, id_pc ) rn
               , case when date_char = '일' 
                      then trunc ( to_date ( day_num, 'rrrr/mm/dd' ) - 1, 'iw' )
                      else trunc ( to_date ( day_num, 'rrrr/mm/dd' ), 'iw' ) 
                  end iw
            FROM t
) t
 WHERE rn = 1
 ORDER BY day_num, id_pc