Cleaning up all accumulated data for a given site

I am a new user of piwik and web-analytics in general.
I am trying to understand various functionality and even some terms of piwik.

I use implort_logs to import the data in piwik.

I could not figure out how can I clean up data accumulated for a given site and try out few things from scratch.

Right now I am resorting to either deleting and recreating the site, which is painful, or uploading the data again, which kind of distorts the whole analytics.

Thanks and Regards,

By cleaning up you mean to remove the data from the database?
Then you have to DELETE all data for the given “idsite” from all the different archive and log tables.