Libgnomedb has an example application similar to the gtk-demo program found in the GTK+ source files. The gnome-db-demo resides in the extra/demos/ directory of the libgnomedb's source distribution.
The demo program uses a small SQLite file database (in the demo_db.db file in the same directory) which represents a classic company's customers sales database (albeit very simplified).
Simply run ./gnome-db-demo to start the demo.
Here are a few examples below: