Example: Unbounded Preceding and Unbounded Following

In this example, the window frame can include all rows in the partition. The query calculates max(sales) sale over the entire partition (no duplicate rows in a month).

SELECT prod_id, month_num, sales, SUM(sales) OVER
  (PARTITION BY prod_id ORDER BY month_num ROWS
  BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
FROM sale WHERE rep_id = 1 
ORDER BY prod_id, month_num;

prod_id   month_num       sales    SUM(sales)
-------   ---------       -----    ----------
10                1         100           680
10                2         120           680
10                3         100           680
10                4         130           680
10                5         120           680
10                6         110           680
20                1          20           156
20                2          30           156
20                3          25           156
20                4          30           156
20                5          31           156
20                6          20           156
30                1          10            34
30                2          11            34
30                3          12            34
30                4           1            34

The query in this example is equivalent to:

SELECT prod_id, month_num, sales, SUM(sales) OVER
  (PARTITION BY prod_id ) 
FROM sale WHERE rep_id = 1 
ORDER BY prod_id, month_num;