We use the .NET SDK to integration our application, but it ships with a chart showing the capabilities of all 3 programming interfaces (.NET, COM and OLEDB/ODBC). All 3 interfaces claim they can read the Sales Invoice data. So, if you're comfortable with and wish to continue to use the ODBC interface, then maybe you should dig deeper in to that documentation. Can you see any tables?

There's a post right around the same date as yours with a question on the SDK. It used to be at a static URL (which most search engines still have cached) but that has seemingly changed recently.