WITH t AS
(
SELECT '20130430' dt, 'N' wday, '' hday FROM dual
UNION ALL SELECT '20130501', 'Y', '' FROM dual
UNION ALL SELECT '20130502', 'N', '' FROM dual
UNION ALL SELECT '20130503', 'N', '' FROM dual
UNION ALL SELECT '20130504', 'Y', '' FROM dual
UNION ALL SELECT '20130505', 'Y', 'Y' FROM dual
UNION ALL SELECT '20130506', 'N', '' FROM dual
UNION ALL SELECT '20130507', 'N', '' FROM dual
UNION ALL SELECT '20130508', 'N', '' FROM dual
UNION ALL SELECT '20130509', 'N', '' FROM dual
UNION ALL SELECT '20130510', 'N', '' FROM dual
)
SELECT *
  FROM (SELECT dt, wday, hday, dy
             , CASE WHEN  LAG(yn) OVER(ORDER BY dt) = 'Y'
                     AND LEAD(yn) OVER(ORDER BY dt) = 'Y'
                    THEN 'Y' ELSE yn END yn
          FROM (SELECT dt, wday, hday
                     , TO_CHAR(TO_DATE(dt, 'yyyymmdd'), 'dy') dy
                     , CASE WHEN wday = 'Y'
                              OR hday = 'Y'
                              OR TO_CHAR(TO_DATE(dt, 'yyyymmdd'), 'd') IN ('6','7','1') -- 금토일
                            THEN 'Y' ELSE 'N' END yn 
                  FROM t
                 WHERE dt >= TO_CHAR(TO_DATE(:sdt, 'yyyymmdd')-1, 'yyyymmdd') -- 검색시작일 하루전
                   AND dt <= TO_CHAR(TO_DATE(:edt, 'yyyymmdd')+1, 'yyyymmdd') -- 검색종료일 하루후
                )
        )
 WHERE dt >= :sdt -- 검색시작일
   AND dt <= :edt -- 검색종료일
;