Django Python Query Join

Question

class Service(models.Model):
      invoice = models.Charfield()

class Sparepart(models.Model):
      name = models.Charfield()
      service = models.Foreignkey(Service)

class SparepartDetail(models.Model):
      type = models.Charfield()
      qty = models.IntegerField()
      sparepart = models.Foreignkey(Sparepart)

Как сделать так, чтобы запрос соединялся так:

FROM service 
LEFT OUTER JOIN sparepart ON (
    service.id = sparepart.service_id
) 
LEFT OUTER JOIN sparepartdetail ON (
    sparepart.id = sparepartdetail.sparepart_id AND sparepartdetail.type = 'USED'
)