Example: Window Frame for RANGE

This query illustrates the RANGE window frame. The number of rows used in the summation is variable.

SELECT prod_id, month_num, sales, SUM(sales) OVER
  (PARTITION BY prod_id ORDER BY month_num RANGE
  BETWEEN 1 FOLLOWING AND 3 FOLLOWING) 
FROM sale 
ORDER BY prod_id, month_num;

prod_id   month_num       sales    sum(sales)
-------   ---------       -----    ----------
10                1         100           350
10                1         150           350
10                2         120           381
10                3         100           391
10                4         130           261
10                5         120           110
10                5          31           110
10                6         110        (NULL)
20                1          20            85
20                2          30            86
20                3          25            81
20                4          30            51
20                5          31            20
20                6          20        (NULL)
30                1          10            25
30                2          11            14
30                3          12             2
30                4           1        (NULL)
30                4           1        (NULL)