Using the Window Functions : Window Functions « Analytical Functions « Oracle PL/SQL Tutorial

Window functions calculates things like

1. cumulative sums,
2. moving averages within a specified range of rows,
3. a range of values, or
4. an interval of time.

Window function can work with: SUM(), AVG(), MAX(), MIN(), COUNT(), VARIANCE(), and STDDEV().

Window function can also work with FIRST_VALUE() and LAST_VALUE(), which return the first and last values in a window.