500 Internal Server Error

oracle.apps.fnd.common.AppsException: oracle.apps.fnd.common.PoolException: Exception creating new Poolable object.

If you are getting the above error while running the page from Jdeveloper that means you have opened so many sessions and not logged out them.

For this you will have to ask DBA to kill the sessions.

Once you start running page from JDeveloper, every time log out instead of directly closing the window.

How to find out nth highest salary of an employee

SELECT Salary, id
FROM
(
SELECT Salary,id,DENSE_RANK() OVER(ORDER BY Salary ASC) Row_numbr from emp1
) tbl
WHERE Row_numbr=n

In the above example if you want to find out the 3rd higest salary of an employee, then pass 3 in place of n.