Oracle，获取2个日期间有多少个周六和周日

函数：

CREATE OR REPLACE FUNCTION count_weekend(start_date IN DATE, end_date IN DATE)
RETURN NUMBER IS V_COUNT INT;
BEGIN
SELECT count(*) INTO V_COUNT
  FROM (SELECT start_date + num - 1,
               TO_CHAR(end_date + num - 1, 'DAY') as t_date2
          FROM (SELECT rownum as num FROM obj)
         WHERE start_date + num - 1 <= end_date)
 WHERE t_date2 in ('星期六', '星期日');
IF NVL(V_COUNT,0) > 0 THEN
    RETURN (V_COUNT);
  ELSE
    RETURN (0);
END IF;
EXCEPTION
  WHEN OTHERS THEN
     RETURN (-1);
END ;