These notes on how to reset the database for Koha were derived from the following email thread: http://lists.koha-community.org/pipermail/koha-devel/2009-January/008939.html and http://lists.katipo.co.nz/public/koha/2014-June/039701.html
Resetting the database may be useful if you install Koha with the sample data, and then wish to use real data without reinstalling the software.
Use your preferred MySQL client to delete the following tables:
You may need to disable foreign key checks to delete data from same tables. For instructions follow this thread: https://lists.katipo.co.nz/pipermail/koha/2013-July/036853.html.