SELECT
    Personal.pers_id,
    Personal.pers_name,
    Personal.pers_vorname,
    Hilfsabfrage.sortier_kriterium
FROM
    Personal LEFT JOIN (
      SELECT
         pers_id
      FROM
         sortierung
      WHERE
         sortierer_id = 1912 AND
         sortier_anwendung = 284
      ORDER BY
         sortier_kriterium
    ) AS Hilfsabfrage
      ON
         Personal.pers_id = Hilfsabfrage.pers_id
WHERE
    Personal.pers_struktur_id = 132 AND
    Personal.pers_aktiv = 1
ORDER BY
    Hilfsabfrage.sortier_kriterium,
    Personal.pers_name,
    Personal.pers_vorname