Ask HN: SQL Help

I work for a company where a new feature will be launched. Let's call the existing feature A and the new feature B. We want to track the adoption of new users for the new feature B. Using SQL, how can I get the new account ids for the new feature B that have no usage on existing feature A. In other words, how can I get the new account that are being signed up for feature B that do not signed up for feature A?