Query to select Users and their Roles

SELECT
   UPPER(pu.username) username,
   trunc(pu.creation_date) user_creation_date,
   prd.role_name,
   trunc(pur.creation_date) creation_date 
FROM
   per_users pu,
   per_user_roles pur,
   per_roles_dn_tl prd 
WHERE
   pu.user_id = pur.user_id ( + ) 
   AND prd.role_id ( + ) = pur.role_id 
   AND pu.active_flag = 'Y'  /* The conditions to the left make sure that the users returned are Active*/
   AND pu.suspended = 'N' 
ORDER BY
   UPPER(pu.username),
   prd.role_name,
   creation_date