Advanced FetchXML SSRS reports for Dynamics CRM
Using the report wizard somebody can create quite useful reports, but as soon as the requirements go just beyond the capabilities of this wizard, one will need to take that report and start modifying the report in SSRS. As the reports are built with FetchXML, this is another topic to think about.
Luckily there are good tutorials online on how to create and author FetchXML based reports. Some of the links that I found particularly interesting are mentioned below. Based on these I have been able to create reports existing out of half a dozen data sets (yes, all FetchXML) and pulling data from each of the datasets to show in the Report Wizard generated report.
Gareth Tucker's "Getting Started with CRM 2011 Online Fetch XML Reporting"
The Microsoft Dynamics CRM Blog's "Fetch-Xml based Reports: Bits & Pieces"
As mentioned in the Microsoft blog, you can hook up multiple datasets. Another approach would be to pull data from another data source. Have a look at the Lookup and LookupSet Functions for this. Note, that perfectly combines with the FetchXML aggregation features.
Good luck with the next level of reporting!