Comparing Nullable values in PostgreSQL

PostgreSQL treats NULL values a bit different than most of the languages we work with. Said that, if you try this:

SELECT * FROM users WHERE has_confirmed_email <> TRUE

This would return users with has_confirmed_email = FALSE only, so NULL values that you have on your DB would be ignored. In this case if you want to get users with has_confirmed_email as FALSE or NULL then you can use IS DISTINCT FROM:

SELECT * FROM users WHERE has_confirmed_email IS DISTINCT FROM TRUE