The team working on the Govt.nz beta have just released a module to help transfer databases between environments.
Once installed and configured replicant will allow you to select an environment to fetch a database from and restore it to a different environment.
Installation is as simple as running the following from your site directory:
composer require govtnz/replicant dev-master
The GitHub repository can be found here: [url]https://github.com/GOVTNZ/replicant[/url]