Multiple sql tables in one dataprovider

Hi, does enybody now how to get content from few tables and put it in one dataprovider for viewing and managing?

or maybe you now where i can find information about it?

Usually I create a dataprovider for the main table and then I use the data of the related table.

If you need to use sort on related field, just add with and toghether in the crieria for the dataprovider.