oracle sql 生日提醒 (兼容跨年)

SELECT *
  FROM TAB C
 WHERE TO_DATE((CASE
                 WHEN TO_CHAR(SYSDATE, 'mm') = '12' AND
                      TO_CHAR(BIRTHDAY, 'mm') = '01' THEN
                  TO_CHAR(SYSDATE + 31, 'YYYY')
                 ELSE
                  TO_CHAR(SYSDATE, 'YYYY')
               END) || '-' || TO_CHAR(BIRTHDAY, 'MM-DD'),
               'YYYY-MM-DD') BETWEEN SYSDATE AND SYSDATE + 30
   AND BIRTHDAY IS NOT NULL;

 上面是查询30天内过生日的员工(30可以该成自己想要的天数)`