MySQL Function for Calculating the Working Days between 2 Dates: https://blag.kazeno.net/development/mysql-function-for-calculating-the-working-days-between-2-dates

workdaysdatediff_declaration.sql

DELIMITER $$
  CREATE FUNCTION WORKDAYSDATEDIFF (date1 DATE, date2 DATE, workdays VARCHAR(7)) 
  RETURNS INT DETERMINISTIC
  /* Calculates working days between 2 dates, work days are supplied as a string with numbers from 0-6 corresponding to WEEKDAY, for example Mon-Fri would be '01234' */
  BEGIN 
    DECLARE date_start DATE;
    DECLARE date_end DATE;
    DECLARE total_days INT;
    DECLARE weeks INT;
    DECLARE start_weekday INT;
    DECLARE end_weekday INT;
    DECLARE count INT;
    DECLARE iter INT;
    IF (date1 IS NULL OR date2 IS NULL OR DATE('0000-00-00') IN(date1, date2)) THEN RETURN -1; END IF;
    SET date_start = LEAST(date1, date2);
    SET date_end = GREATEST(date1, date2);
    SET total_days = DATEDIFF(date_end, date_start);
    SET weeks = FLOOR(total_days/7);
    SET start_weekday =  WEEKDAY(date_start);
    SET end_weekday =  WEEKDAY(date_end);
    SET count = CHAR_LENGTH(workdays)*weeks;
    IF (MOD(total_days, 7) = 0) THEN RETURN count; END IF;
    SET iter = start_weekday;
    LOOP
      IF (iter = end_weekday) THEN RETURN count; END IF;
      IF (INSTR(workdays, CONCAT(iter)) > 0) THEN SET count = count +1; END IF;
      IF (iter > 5) THEN SET iter = 0; ELSE SET iter = iter +1; END IF;
    END LOOP;
  END$$
  DELIMITER ;

workdaysdatediff_usage.sql

SELECT WORKDAYSDATEDIFF ('2019-07-05', '2019-08-05', '01234')