How to import an SQL file and COMPLETELY erase the previous one
You can use drush:

drush sql-drop; drush sqlc &lt; path/to/sql/dump/file.sql


Understand it will drop your entire Drupal db and the second command will rebuild it from your dump file.

You can create a base dump from:

drush sql-dump &gt; path/to/save/dump.sql


Here's the link to the drush commands website, select sql from the menu on the left drush commands