I have a CSV file with email addresses i want to import into Wordpress.coms Jetpack subscriptions.
WordPress.com Jetpack subscriptions are not hosted on your site, they're hosted on the WordPress.com servers. So you can't add directly to the database.
However, if you take a look at the Jetpack plugin code, it outlines the XML-RPC calls used to interface with WordPress.com and add subscribers. So you could build your own importer ...