Magic Data and Uber List access data from the c5 core tables, eCommerce (via MD Commerce), core forms and CSV files (via MD Forms), marketplace packages (via MD Developer).

So if your data is in any table already accessed by the above, you have access to it already.

If you are looking at joining some application specific tables that are not already covered by the above, you have three approaches available, the first two involving a little php.

1. Code some new MD symbols to list the results of your query, identify an individual item in the query and access properties of that item That is how many existing sets of symbols work. For example, list pages, identify a page, page name, page description, page attribute etc. And similar for Users, Files, Products, Form results.

Symbols are very simple php files, inheriting from a base class and providing a few methods. There is some guidance in the docs pages and plenty of commented examples within the various MD packages.

2. Code a new form interface layer, using the core forms or CSV interface as an example. A form interface layer is a bit more complicated than a new symbol, but follows a similar approach by providing a class that inherits from a base. It maps whatever data is being interfaced as a grid of rows and columns with some standard methods to access the grid (so the core forms interface involves various joins and the CSV interface is a simple grid). Once provided, all the facilities of MD Forms, Uber List and Uber Filter are immediately available for the new form interface.

3. If the data is not particularly volatile, use phpMyAdmin to export a snapshot of the join to a csv file, then use the MD forms CSV interface to access the data via the CSV.

If you can provide me with a little more detail, I can advise further.