Can I just ask to compare based on the year and month?
You can. Here's a simple example using the AdventureWorks sample database...
DECLARE @Year INT
DECLARE @Month INT
SET @Year = 2002
SET @Month = 6
SELECT
[pch].*
FROM
[Production].[ProductCostHistory] pch
WHERE
YEAR([pch].[ModifiedDate]) = @Year
AND MONTH([pch].[ModifiedDate]) = @Month