WITH t AS
(
SELECT '20150701' dt, 'A' cd FROM dual
UNION ALL SELECT '20150702', 'B' FROM dual
UNION ALL SELECT '20150705', 'C' FROM dual
UNION ALL SELECT '20150714', 'D' FROM dual
)
SELECT *
  FROM t a
     , (-- 입력 : 년도(2015), 주차(28)
        -- 출력 : 해당주의 시작일(20150705), 종료일(20150711)
        SELECT TO_CHAR(GREATEST(sdt, TRUNC(sdt,'d')+ww*7-7),'yyyymmdd') sdt
             , TO_CHAR(LEAST   (edt, TRUNC(sdt,'d')+ww*7-1),'yyyymmdd') edt
          FROM (SELECT TO_DATE('2015'||'0101', 'yyyymmdd') sdt
                     , TO_DATE('2015'||'1231', 'yyyymmdd') edt
                     , 28 ww
                  FROM dual)
        ) b
 WHERE a.dt BETWEEN b.sdt AND b.edt
;