Inline Views Top N Analysis

The Inline view: It is a construct in Oracle SQL where you can place a query in the SQL FROM, clause, just as if the query was a table name.
A common use for in-line views in Oracle SQL is to simplify complex queries by removing join operations and condensing several separate queries into a single query.

Top N Analysis: The task of retrieving the top or bottom N rows from a database table. You can do so either by using the ROWNUM pseudocolumn available in several versions of Oracle or by utilizing new analytic functions available in Oracle 8i: RANK () and DENSE_RANK ().

Using the ROWNUM PseudocolumnOne-Way to solve this problem is by using the Oracle pseudocolumn ROWNUM. For each row returned by a query, the ROWNUM pseudocolumn returns a number indicating the order in which Oracle selects the row from a table or set of joined rows.
E.g. To select top 5 rows
SELECT Empno, Ename, Job, Mgr, Hiredate, Sal
FROM
(SELECT Empno, Ename, Job, Mgr, Hiredate, Sal
FROM Emp
ORDER BY NVL (Sal, 0) DESC)
WHERE ROWNUM <>