Listing All Months Regardless Of Values

I have written the following query which returns the number of orders received grouped by the year and month:
SELECT DATEPART(yyyy, order_placeddate) AS year, DATEPART(mm, order_placeddate) AS month, count(order_id) AS orders
FROM orders
GROUP BY DATEPART(yyyy, order_placeddate), DATEPART(mm, order_placeddate)
ORDER BY year, month
year month orders
---- ----- ------
2004 6 17
2004 7 37
2004 8 30
2004 9 42
2004 10 34
2004 11 46
2005 1 25
2005 2 7
2005 4 1
The obvious problem with the above is that it misses out the months that have no orders, i.e. December, March, May, etc.

Is there a way I can amend my query so that it shows all months regardless of whether any orders were placed?

I have thought about trying to LEFT OUTER JOIN the above to a table that has rows with values of 1 – 12, but I’m not convinced this is the answer... and I don’t really know how to do it!

Do let me know if any of the above is unclear – what I’m after is the following:
year month orders
---- ----- ------
2004 6 17
2004 7 37
2004 8 30
2004 9 42
2004 10 34
2004 11 46
2004 12 0
2005 1 25
2005 2 7
2005 3 0
2005 4 1
2005 5 0
Many thanks