WITH t AS 
( 
       SELECT * 
       FROM  ( 
                       SELECT   salary, 
                                Dense_rank() over (ORDER BY salary DESC) dr 
                       FROM     employees ) 
       WHERE  dr <=5 ) ,c AS 
select * 
FROM  ( 
                SELECT   salary, 
                         dense_rank() over (ORDER BY salary ASC) ar 
                FROM     employees ) 
WHERE  ar <=5 
SELECT t.employee_id AS top5 , 
       c.employee_id AS bottom5 
FROM   t, 
       c 
WHERE  t.dr =c.ar and order by t.salary ;

WITH t AS 
( 
         SELECT   salary, 
                  Dense_rank() OVER (ORDER BY salary DESC) dr 
         FROM     employees ) where dr <=5 ),c AS 
( 
         SELECT   salary, 
                  dense_rank() OVER (ORDER BY salary ASC) ar 
         FROM     employees ) WHERE dr <=5 )SELECT t.employee_id AS top_5_bid , 
       c.employee_id AS bottom_5_id 
FROM   t 
UNION ALL 
          c 
WHERE     t.dr =c.ar 
AND       t.dr <=5 
ORDER BY  t.dr;

SELECT * 
FROM   ( 
                SELECT   salary, 
                         Dense_rank() over (ORDER BY salary DESC) dr 
                FROM     employees ) 
WHERE  dr <=5 ) 
UNION 
SELECT * 
FROM   ( 
                SELECT   salary, 
                         dense_rank() over (ORDER BY salary ASC) ar 
                FROM     employees ) 
WHERE  ar <=5);

SQL> select employee_id, salary
  2  from ( select employee_id, salary,
  3                dense_rank() over (order by salary asc) rk1,
  4                dense_rank() over (order by salary desc) rk2
  5         from employees )
  6  where rk1 <= 5 or rk2 <= 5
  7  order by 2, 1
  8  /
EMPLOYEE_ID     SALARY
----------- ----------
        132       2100
        128       2200
        136       2200
        127       2400
        135       2400
        119       2500
        131       2500
        140       2500
        144       2500
        182       2500
        191       2500
        118       2600
        143       2600
        198       2600
        199       2600
        201      13000
        146      13500
        145      14000
        101      17000
        102      17000
        100      24000

21 rows selected.