How to Change the Post Attribution at WordPress – The solution. Modifying author attribution on each post takes a lot of time. Happily, SQL can help you get things done:
1. Log in to your phpMyAdmin and select your WordPress database.
2. First, we have to get the right user IDs. To do so, open the SQL command window and execute the following command:
SELECT ID, display_name FROM wp_users;
UPDATE wp_posts SET post_author=NEW_AUTHOR_ID WHERE post_author=OLD_AUTHOR_ID;
Job is done !