This section provides additional examples using the OLAP functions.
Both start and end points of a window may vary as intermediate result rows are processed. For example, computing a cumulative sum involves a window with the start point fixed at the first row of each partition and an end point that slides along the rows of the partition to include the current row. See Figure 2-3.
As another example, both the start and end points of the window can be variable yet define a constant number of rows for the entire partition. Such a construction lets users compose queries that compute moving averages; for example, a SQL query that returns a moving three-day average stock price.
