SQL Aggregate Concatenation

create table Stu(Id varchar(2), Name varchar(15), 
Class  varchar(10),sub_id varchar(2),marks varchar(3));

insert into Stu values(1,'Komal',10,1,45);
insert into Stu values(2,'Ajay',10,1,56);
insert into Stu values(3,'Rakesh',10,1,67);
insert into Stu values(4,'Santosh',10,1,67);

insert into Stu values(1,'Komal',10,2,47);
insert into Stu values(2,'Ajay',10,2,53);
insert into Stu values(3,'Rakesh',10,2,57);
insert into Stu values(4,'Santosh',10,2,67);
insert into Stu values(5,'Bhanu',10,2,67);

insert into Stu values(1,'Komal',10,3,45);
insert into Stu values(2,'Ajay',10,3,56);
insert into Stu values(3,'Rakesh',10,3,67);
insert into Stu values(4,'Santosh',10,3,67);
insert into Stu values(5,'Bhanu',10,3,67);

insert into Stu values(1,'Komal',10,4,65);
insert into Stu values(2,'Ajay',10,4,56);
insert into Stu values(3,'Rakesh',10,4,37);
insert into Stu values(4,'Santosh',10,4,67);
insert into Stu values(5,'Bhanu',10,2,67);

insert into Stu values(1,'Komal',10,5,65);
insert into Stu values(2,'Ajay',10,5,46);
insert into Stu values(3,'Rakesh',10,5,63);

mysql> select id, name, GROUP_CONCAT(marks order by sub_id)
    -> from stu  group by id;
+------+---------+-------------------------------------+
| id   | name    | GROUP_CONCAT(marks order by sub_id) |
+------+---------+-------------------------------------+
| 1    | Komal   | 45,47,45,65,65                      |
| 2    | Ajay    | 56,53,56,56,46                      |
| 3    | Rakesh  | 67,57,67,37,63                      |
| 4    | Santosh | 67,67,67,67                         |
| 5    | Bhanu   | 67,67,67                            |
+------+---------+-------------------------------------+
5 rows in set (0.00 sec)