Dear Adriano,
I have copy&pasted the code from the tutorial. And I have created the same articles with the same parametres.I have just added the sku manually(1-4).
I want you to see the images. the first one is the view. The other one is the Select query(I have it Numeric), and the third one is the result.
Here ar the links:
http://imgur.com/eVHQvaB
http://imgur.com/GYgHYPj
http://imgur.com/ZljZEME