计算某一天是当月第几周

SELECT CEIL((TO_NUMBER(SUBSTR('20090905', -2), 99) +
            (TO_NUMBER(TO_CHAR(TO_DATE(SUBSTR(20090905, 1, 6) || '01',
                                        'YYYYMMDD'),
                                'D'),
                        99) - 1)) / 7)
 FROM dual;