For convenience to test Database Browser online, a sample cloud database is provided below for use. You can use it to get familiar with Database Browser.
Test Connection Details
Database Type : MySQL
Host : us-cdbr-iron-east-03.cleardb.net
Database Name : heroku_eac377a18b009b8
User Name : bd0617aba4eb0d
Password : cc31163c
This database has an invoice table, which you can query.
(Please note that above is a sandbox environment. Availability is not guaranteed)