How to use rownum

I have a employee table in oracle with name,salary and other details.

I am trying to get the second highest salary but not able to fetch.

This one working fine

with e_salary as (select distinct salary from employee)
select salary from e_salary
order by salary desc

And gives output:

but when i am using the same query to fetch second highest row not getting any output

select salary
  from ( with e_salary as (select distinct salary from employee)
         select salary from e_salary order by salary desc)
 where rownum = 2

but as i replace the rownum=2 with rownum<2 it gives output of first two records. Please someone explain why rownum=2 is not working

Solution

This will work:

select salary from ( select salary , rownum as rn from (select salary from e_salary order by salary desc)) where rn = 2;

Why it doesn't work:

When assigning ROWNUM to a row, Oracle starts at 1 and only only increments the value when a row is selected; that is, when all conditions in the WHERE clause are met. Since our condition requires that ROWNUM is greater than 2, no rows are selected and ROWNUM is never incremented beyond 1.

Hope u are clear right now.