How to findout Nth Highest salary

Select sal from emp a

Where &n = (select count(*) from emp b

                       Where a.sal <= b.sal);

To find the 3rd highest salary of emp table:

Select a.sal from emp a

Where 3 = (select count(*) from emp b

                       Where a.sal <= b.sal);

Without Duplicate:

Select distinct(a.sal) from emp a

Where 3 = (select count(distinct(b.sal)) from emp b

                       Where a.sal <= b.sal);

To find the first 3 highest salaries (show all 3 salaries):

Select sal from emp a

  Where 2 >=  (select count(*) from emp b

  Where a.sal < b.sal);

Without Duplicate:

Select distinct (a.sal) from emp a

Where 2 >= (select count(distinct b.sal) from emp b

Where a.sal <= b.sal);