django inner joins

//models
#Questions model
class Qns(models.Model):
     qn = models.TextField()
     ref = models.TextField(null=True)

     class Meta:
        verbose_name_plural="qns"
     def __unicode__(self):
        return self.qn

#themes
class Themes(models.Model):
    """Model for quiz themes or categories. Each qn should belong to a theme"""
    theme = models.TextField()
    description = models.TextField(null=True)
    author = models.CharField(max_length=255, null=True)

    class Meta:
        verbose_name_plural="themes"
    def __unicode__(self):
        return self.theme

#themes-questions map
class QnsThemes(models.Model):
    """Models many-to-many relationship between theme and Questions"""
    qn = models.ForeignKey(Qns)
    theme = models.ForeignKey(Themes)

    class Meta:
        verbose_name_plural="qns_themes"
    def __unicode__(self):
        return self.theme

"""
How do i do an inner join between the Qns models and the QnsThemes models like
select qns.qn_id, qns.qn, qns.ref from themes_qns inner join qns on qns.qn_id = qns_themes.qn_id  where qns_themes.theme_id = 1 order by qns.qn_id asc

"""