How to get unique records without using “DISTINCT” in oracle

drop table Student_list;
create table Student_list(roll_no number, stu_name varchar2(30));

Insert into Student_list (ROLL_NO,stu_name) values (1,'KING');
Insert into Student_list (ROLL_NO,stu_name) values (2,'BLAKE');
Insert into Student_list (ROLL_NO,stu_name) values (3,'CLARK');
Insert into Student_list (ROLL_NO,stu_name) values (4,'JONES');
Insert into Student_list (ROLL_NO,stu_name) values (5,'SCOTT');
Insert into Student_list (ROLL_NO,stu_name) values (6,'RAGHU');
Insert into Student_list (ROLL_NO,stu_name) values (7,'FORD');
Insert into Student_list (ROLL_NO,stu_name) values (8,'SMITH');
Insert into Student_list (ROLL_NO,stu_name) values (9,'ALLEN');
Insert into Student_list (ROLL_NO,stu_name) values (10,'WARD');
Insert into Student_list (ROLL_NO,stu_name) values (1,'KING');
Insert into Student_list (ROLL_NO,stu_name) values (5,'SCOTT');
Insert into Student_list (ROLL_NO,stu_name) values (7,'FORD');

COMMIT;

---

select * from Student_list
order by roll_no,stu_name;

---

SELECT DISTINCT ROLL_NO,STU_NAME
FROM STUDENT_LIST
ORDER BY ROLL_NO,STU_NAME;

---

SELECT UNIQUE ROLL_NO,STU_NAME
FROM STUDENT_LIST
ORDER BY ROLL_NO,STU_NAME;

---

SELECT ROLL_NO,STU_NAME
FROM STUDENT_LIST
GROUP BY ROLL_NO,STU_NAME
ORDER BY ROLL_NO,STU_NAME;

---

SELECT ROLL_NO,STU_NAME
FROM STUDENT_LIST
UNION 
SELECT ROLL_NO,STU_NAME
FROM STUDENT_LIST;

---

SELECT ROLL_NO,STU_NAME
FROM STUDENT_LIST
UNION 
SELECT NULL,NULL
FROM DUAL WHERE 1=2;

---

SELECT ROLL_NO,STU_NAME
FROM STUDENT_LIST
INTERSECT
SELECT ROLL_NO,STU_NAME
FROM STUDENT_LIST;

---

SELECT ROLL_NO,STU_NAME
FROM STUDENT_LIST
MINUS
SELECT NULL,NULL
FROM DUAL;

---

SELECT ROLL_NO,STU_NAME FROM (
SELECT ROLL_NO,STU_NAME,
    ROW_NUMBER() over(partition by ROLL_NO,STU_NAME 
                      ORDER BY ROLL_NO,STU_NAME) R
FROM STUDENT_LIST)
where R=1;

---

SELECT ROLL_NO,STU_NAME FROM (
SELECT ROLL_NO,STU_NAME,
    RANK() over(partition by ROLL_NO,STU_NAME 
                ORDER BY ROWNUM) R
FROM STUDENT_LIST)
where R=1;

---

SELECT * FROM STUDENT_LIST
WHERE ROWID IN (
SELECT MIN(ROWID)
FROM STUDENT_LIST
GROUP BY ROLL_NO,STU_NAME)
ORDER BY ROLL_NO,STU_NAME;

---

SELECt * FROM STUDENT_LIST A
WHERE 1 = ( SELECT COUNT(1) 
            FROM STUDENT_LIST B 
            WHERE A.ROLL_NO = B.ROLL_NO
            AND A.STU_NAME = B.STU_NAME
            AND A.ROWID >= B.ROWID);

---