Wordpress Change Default Display Name Publicy As for all existing users

Question

does anyone know of way I can change the existing display name publicly as for all users. I want to have firstname lastname as the default because this will reflect in the forum

Answer 1

A old question but my answer might be usefull for someone else.

Run this query on your database (adjust table names if you have another prefix):

UPDATE wp_users SET display_name = CONCAT((SELECT meta_value FROM wp_usermeta WHERE meta_key = 'first_name' AND user_id = ID), ' ', (SELECT meta_value FROM wp_usermeta WHERE meta_key = 'last_name' AND user_id = ID));

On WP 3.3.1 but should work on later versions.