How to use external data grouped and joined with AX data in a SSRS report

Hi,

I'm very new to AX reporting so apologies if my question is a little basic.

I need to produce a SSRS report in AX 2012 which uses data from a legacy system outside of AX along with data from AX 2012. These two data sources need to be joined and grouped to create a single dataset that I can then use to produce my resultant table in the report. I cannot figure out how to accomplish this.

I've created a query in the AOT which gives me the AX dataset and added this to my report project. I've also created a data source in the report project which gives me the legacy dataset, now I just need to join and group them to give me the dataset I need to bind the table to. Can someone please explain how I do this?

I've seen in standard SSRS Report Models where a Dataset view can be created from multiple datasources, is this possible in an AX report model, or am I barking up the wrong tree?

Thanks in advance.