Restore WordPress database from backup

Hi. I need to restore my site back to its previous state after a disastrous set of updates broke some things on the site. I have a db backup taken using phpmyadmin and a site backup so I should be OK. I have a question though.

When restoring the database, should I delete all the currently existing tables first? The codex instructions imply that this is not necessary, but nearly everything else I’ve read suggests it is.

The sql says to create the table if it doesn’t exist, but doesn’t say to drop it if it does, so I’m not sure how the import would work.

Thanks in advance

PAE