SQL Aggregate Sum

create table Stu_Table(Stu_Id varchar(2), Stu_Name varchar(15), 
Stu_Class  varchar(10),sub_id varchar(2),marks varchar(3));

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

insert into Stu_Table values(1,'Komal',10,2,47);
insert into Stu_Table values(2,'Ajay',10,2,53);
insert into Stu_Table values(3,'Rakesh',10,2,57);

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

insert into Stu_Table values(1,'Komal',10,4,65);
insert into Stu_Table values(2,'Ajay',10,4,56);
insert into Stu_Table values(3,'Rakesh',10,4,37);

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

+--------+----------+-----------+--------+-------+
| Stu_Id | Stu_Name | Stu_Class | sub_id | marks |
+--------+----------+-----------+--------+-------+
| 1      | Komal    | 10        | 1      | 45    |
| 2      | Ajay     | 10        | 1      | 56    |
| 3      | Rakesh   | 10        | 1      | 67    |
| 1      | Komal    | 10        | 2      | 47    |
| 2      | Ajay     | 10        | 2      | 53    |
| 3      | Rakesh   | 10        | 2      | 57    |
| 1      | Komal    | 10        | 3      | 45    |
| 2      | Ajay     | 10        | 3      | 56    |
| 3      | Rakesh   | 10        | 3      | 67    |
| 1      | Komal    | 10        | 4      | 65    |
| 2      | Ajay     | 10        | 4      | 56    |
| 3      | Rakesh   | 10        | 4      | 37    |
| 1      | Komal    | 10        | 5      | 65    |
| 2      | Ajay     | 10        | 5      | 46    |
| 3      | Rakesh   | 10        | 5      | 63    |
+--------+----------+-----------+--------+-------+

select stu_id, stu_name, sum(marks) as 'total marks' 
from stu_table group by stu_id;

+--------+----------+-------------+
| stu_id | stu_name | total marks |
+--------+----------+-------------+
| 1      | Komal    | 267         |
| 2      | Ajay     | 267         |
| 3      | Rakesh   | 291         |
+--------+----------+-------------+