Python Django两个内连接

我是Django的新手。我有一个mySQL查询：

    SELECT username, foto FROM a INNER JOIN b ON (a.user_id = b.id) INNER JOIN c ON (a.foto_id = c.id) 

如何用Django写

型号：

    class b(models.Model):
        username = models.CharField(max_length=30)
        email = models.CharField(max_length=30)
        password = models.CharField(max_length=30)

    class c(models.Model):
        user_id = models.IntegerField()
        foto = models.FileField(upload_to='documents')
        created_at = models.DateTimeField(auto_now_add=True)

    class a(models.Model):
        user_id = models.IntegerField()
        foto = models.ForeignKey('c', blank=True, null=True)
        created_at = models.DateTimeField(auto_now_add=True)

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我认为您正在寻找：

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我想如果你展示你的模型，这会更容易。

A.objects.select_related('b', 'c').values('b__username', 'c__foto')