mysql查询两个日期之间的工作日天数（仅排除周六日）

创建一个查询工作日天数的函数

DROP FUNCTION IF EXISTS fun_workdaynum;
CREATE FUNCTION fun_workdaynum(start_date Date, end_date DATE)
RETURNS INT(20)
BEGIN
 DECLARE daynum INT(20) DEFAULT 1;
 IF start_date > end_date then
 RETURN -1;
END IF;
 SET daynum =
     case 
       when week(end_date)-week(start_date) = 0 then -- 同个星期
            dayofweek(end_date) - dayofweek(start_date) + 1
          - case 
            when (dayofweek(start_date) > 1 and dayofweek(end_date) < 7) then 0
            when (dayofweek(start_date) = 1 and dayofweek(end_date) =7) then 2
            else 1
            end
       else (52*(year(end_date)-year(start_date)-1)+(52-week(start_date))+week(end_date)-1)*5 -- 跨星期/跨年份
          + case 
            when dayofweek(start_date) = 1 then 5
            when dayofweek(start_da