How To Force 12 Rows (1) Per Month

i have a datatable with Part , DateSold,ItemsSold
i want to show the sales for the last 12 months by month. if there were no sales for a given month i want the table to show 0.


here was my first attemp that only gives me data if all twelve months had sales.

SELECT MONTH(DateSold) AS Month, SUM(ItemsSold) AS ThisYear
FROM inv_Monthly_Sales
WHERE (YEAR(DateSold) = @Yr - 1) AND (Part = @Part)
GROUP BY MONTH(DateSold)
ORDER BY Month


i tried using isnull with the sum but that didn't work.
how can i force the table to always generate a dummy table of 12 months and then left join to it and in that way force it to give 12 moths of sales even when it does'n exist.


your help is greatly appreciated,
slimshim