SQL> select * from emp3;

EMPLOYEE_ID LAST_NAME                SALARY JOB_ID     DEPARTMENT_ID
----------- -------------------- ---------- ---------- -------------
          1 Ram                         100 X                     11
          2 Shyam                       200 Y                     12
          2 Shyam                       300 Y                     12
          2 Neelesh                     400 Y                     12

SQL> SELECT /*+ FIRST_ROWS(1) */ employee_id, last_name, salary, job_id
  2    FROM emp3
  3    WHERE department_id = 12;

EMPLOYEE_ID LAST_NAME                SALARY JOB_ID
----------- -------------------- ---------- ----------
          2 Shyam                       200 Y
          2 Shyam                       300 Y
          2 Neelesh                     400 Y


SQL> SELECT /*+ ALL_ROWS */ employee_id, last_name, salary, job_id
  2        FROM emp3
  3        WHERE department_id = 12;

EMPLOYEE_ID LAST_NAME                SALARY JOB_ID
----------- -------------------- ---------- ----------
          2 Shyam                       200 Y
          2 Shyam                       300 Y
          2 Neelesh                     400 Y