What should work: Add a reference to an external file in RoboHelp (a php file for example). The external file must then present the information from the database while for the user it will seem that his file is part of the help output.
One note: If you want users to be able to find this file in the search, you must set up external context search in the project. (Link relevant search terms to the page.)
Another possibility is to generate a static HTML file from the database and import that in RoboHelp. Update the HTML file whenever the content of the db changes.