Regardless of version of SSRS (2005 or 2008), it is not possible to combine different datasets e.g. SQL Server database dataset, SSAS cube dataset, and XML feed.
Some ways to achieve this would be to do this in the database during the data source retrieval.
Use Linked Servers/CLR Routines/OPENROWSET/OPENDATASOURCE options to combine the dataset.
Another option if you want to use different datasets, but only want to display the data separately (i.e. not in the one data region), use Subreports.
Another possible way is use Lookup function inside SSRS 2008
Syed Qazafi Anjum
I am facing a similar issue. I have two Measures.There are few common fields and one unrelated field. I am trying to have two datasets for each measure so that I can display the unique field. If we need to show the entire data in a tablix and working on Cube
data, could you suggest me a possible way to achieve this? Can I use Custom code to combine the queries?