I have a query of running sum with partition. It fetches the 4 weekly running sum of the dataset with current row and 3 rows below. My problem is that the dataset has gaps and doesn't have all weeks in the data which causes my running sum to be incorrect. Can i use SQL to fill in the missing weeks so my 4 week running sum to be accurate. In the below example data for 26/10 and 2/11 is missing so my 4 week future running sum is inaccurate

Sample Data

```
Item_No Week_Starting_Monday    Cover_Weeks Four_Weeks_Cover
6-KDDDORF   20201012    3   8
6-KDDDORF   20201019    2  9
6-KDDDORF   20201109    1   12
6-KDDDORF   20201116    2   11
6-KDDDORF   20201123    4   9
6-KDDDORF   20201130    5   5

```

Desired Data

```
Item_No Week_Starting_Monday    Cover_Weeks Four_Weeks_Cover
6-KDDDORF   20201012    3   5
6-KDDDORF   20201019    2   3
6-KDDDORF   20201109    1   12
6-KDDDORF   20201116    2   11
6-KDDDORF   20201123    4   9
6-KDDDORF   20201130    5   5

```

Query

```
      SELECT t.*,
                SUM(Cover_Weeks) OVER (PARTITION BY Item_No, (seqnum - 1) / 4)  AS Four_Weeks_Cover
        FROM (SELECT t.*,
                     ROW_NUMBER() OVER (PARTITION BY Item_No ORDER BY Week_Starting_Monday) - 1 as seqnum
              FROM Table_Name t
             ) t;

```