SELECT u.ID, u.user_login, CONCAT('{', GROUP_CONCAT(CONCAT('"', m.meta_key, '"', ':', '"', m.meta_value, '"')), '}') AS meta_data, (SELECT meta_value FROM wp_usermeta as mt where meta_key = 'last_name' and mt.user_id = u.ID) AS ln
FROM wp_users as u left join wp_usermeta as m on u.ID = m.user_id where m.meta_key IN ('first_name', 'last_name')