select * from (select * from emp order by sal desc) where rownum <= 5;

5th MAX Salary

select max(SALARY) from EMP A where 5=( select count(distinct(SALARY)) From EMP  B where B.ID>=A.ID)

SELECT    empid
             ,empname
             ,salary
             ,RANK() OVER (ORDER BY salary DESC) AS Rank_Salary
FROM emp
QUALIFY Rank_Salary<= 3;

select min(sal) from (select sal from emp order by sal desc) where rownum <=n;

where n is the nth highest salary you want.