SELECT sub.name,
         v.value email
    FROM psx_subjects sub
         LEFT JOIN ((psx_subject_attributes rel
                  INNER JOIN psx_attribute_names n
                          ON rel.attributeid = n.ID
                         AND n.name = 'sys_email')
                  INNER JOIN psx_attribute_values v
                          ON v.attributeid = n.ID)
         ON sub.ID = rel.subjectid
ORDER BY sub.name