Add default rating

This query will only work with post that already have ratings_* custom field in them aka posts that have been created after the plugin was activated. For posts earlier than that, there is no way I can think of.

The query below will give a rating of 5. Note that it is not tested and backup your DB before running the query.
UPDATE wp_options SET option_value = 1 WHERE option_name = 'ratings_users' AND option_value = 0;
UPDATE wp_options SET option_value = 5 WHERE option_name = 'ratings_score' AND option_value = 0;
UPDATE wp_options SET option_value = 5 WHERE option_name = 'ratings_average' AND option_value = 0;