about the only thing you might be able to do is use LOOKUP to get data from the other dataset. Other than that, you'd have to combine them in a query if you absolutely had to have all the data from both in one tablix.

Here's the MS link... not my favorite:

https://msdn.microsoft.com/en-us/library/ee210531.aspx

There's one on YouTube that walks you through it (takes about 5 mins... )