I have googled this and seem to only be able to find the same Tutorial here or variations thereof. I have two lists. Each one is on a different site. I need to make a list/view joining these two lists. One site contains basic employee data, (such as department) and the other site contains details about that department that we need to show on a high level overview of employee data.
It's sharepoint 2007
There are several ways you can do it.
First and simplest: third party tools, you can google tons of such, which, I think, have no much difference. SharePoint List Collection is one of them.
This is another way you can turn to. http://www.c-sharpcorner.com/UploadFile/ssahmed/spslistcol09182006055026AM/spslistcol.aspx.
Aonther way to go is to roll your own field type and make it similar to a lookup field but instead make it go fetch data from a list in a different sitecollection. I don´t have ready example of something like this but this post atleast explains how to go about constructing a custom field type.
I would use Sahil Malil's technique. However this is much the same as the link to Microsoft that you've already given. Why doesn't this do what you need?
I used this tutorial
He mentions "Please note: If your lists are on another site collection you will have to use the Connect to another library... link" and he includes a screenshot.