SQL to run below (change table name to your prefix)
DELETE from ulj_users where ulj_users.ID not in ( SELECT meta_value FROM ulj_postmeta WHERE meta_key = '_customer_user' ) AND ulj_users.ID not in ( select distinct(post_author) from ulj_posts )LIMIT 100; delete from ulj_usermeta where ulj_usermeta.user_id not in (select ID from ulj_users) LIMIT 100;