stringsql=$@"SELECT count(*) AS Num FROM(SELECT OrderGuestId FROM rb_class_check WHERE `Status`=0 AND Group_Id={groupId} AND ClassId ={classId} GROUP BY OrderGuestId)t";
stringsql=$@"SELECT count(*) AS Num FROM(SELECT OrderGuestId FROM rb_class_check WHERE `Status`=0 AND Group_Id={groupId} AND ClassId ={classId} GROUP BY OrderGuestId)t";