A: 

I just tried it with some GA data. It seems to be picky about what metric you join it to but ga:pageviews works. Both ga:campaign and ga:pagePath are dimensions and you need to join them to a metric. You can reference GA documentation here regarding what are the valid combinations. As an example, I managed to retrieve a really long report using (replace with your profile id):

https://www.google.com/analytics/feeds/data?ids=ga:123456&dimensions=ga:campaign,ga:pagePath&metrics=ga:pageviews&sort=ga:campaign,ga:pagePath&start-date=2009-01-01&end-date=2009-06-30

Hope this helps.

megeria
Thanks for your reply. I am trying to execute your sample with my table id, but I cannot get it to work. I am getting an Authorization Required. I am authenticating with Google Analytics before requesting the URI. Let me know if you know what steps to take before executing the script. Thanks again.
Geo
You need to authenticate to GA separately by sending an extra header in the http request. See http://code.google.com/apis/gdata/articles/using_cURL.html and http://code.google.com/apis/analytics/docs/gdata/1.0/gdataProtocol.html
megeria
A: 

If you are using java or servlet, you can use authentication method in analytics api to authenticate first, and then you can retrieve data from the profile of that user. if you need any help, you can contact me on my mail as well. i am too working on the same field.

Deepak Kumar Karna