how to remove the NULL rows of cells?

I've got the following query in the next URL
http://cwebbbi.wordpress.com/2011/05/24/replacing-linkmember-with-a-many-to-many-relationship/

SELECT
[Date Type].[Date Type].[Date Type].MEMBERS
ON 0,
[Date].[Calendar Year].[Calendar Year].MEMBERS
ON 1
FROM [M2MTest]
WHERE([Measures].[Sales Amount])

What is the syntax to prevent showing of the rows of the cells having NULL?

Secondly, How to get the previous year?

SELECT

        [Date Type].[Hierarchy].[Date Type Key].MEMBERS
        ON 0,

//        [Date].[Calendar Date].[Year].MEMBERS  // Hier
        [Date].[Calendar Date].[Year].PREVMEMBER  // Doesn't work. expect member expression
        ON 1

FROM
        [SOS OLAP]
WHERE(    [Measures].[Internet Sales Amount]    )

Executing the query ...
Query (10, 3) The PREVMEMBER function expects a member expression for the 1 argument. A level expression was used.
Execution complete

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