Calculate M-F hours between 2 times in MySQL

weekday_hours.sql

  @new := reports.downloaded_at,
  @old := pages.created_at,
  @oldWeek := WEEK(@old, 2),
  @newWeek := WEEK(@new, 2),
  @weekends := @newWeek - @oldWeek,
  @weekendSecs := @weekends * 172800,
  @oldWeekSaturday := STR_TO_DATE( CONCAT(DATE_FORMAT(@old, '%X%V'), ' Saturday'), '%X%V %W %h-%i-%s'),
  @extraFirstWeekSecs := TIME_TO_SEC( TIMEDIFF(@old, @oldWeekSaturday) ),
  @extraFirstWeekSecs := (@extraFirstWeekSecs > 0) * @extraFirstWeekSecs,
  @newWeekSaturday := STR_TO_DATE( CONCAT(DATE_FORMAT(@new, '%X%V'), ' Saturday'), '%X%V %W %h-%i-%s'),
  @extraLastWeekSecs := TIME_TO_SEC( TIMEDIFF(@new, @newWeekSaturday) ), 
  @extraLastWeekSecs := (@extraLastWeekSecs > 0) * @extraLastWeekSecs,
  @totalSecs := TIME_TO_SEC( TIMEDIFF(@new, @old) ),
  @totalHours := @totalSecs / 3600 as total_hours,
  @avg := (@totalSecs - @weekendSecs + @extraFirstWeekSecs + @extraLastWeekSecs) / 3600 as weekday_hours