Python-сообщество

class Student(models.Model):
    class Meta():
        db_table="student"
    student_name = models.CharField(max_length = 30)
class Rating(models.Model):
    class Meta():
        db_table="rating"
    rating_lesson = models.IntegerField()
    rating_student = models.ForeignKey(Student)

SELECT student_name, (AVG(rating_lesson)) AS rating FROM student
INNER JOIN rating ON rating.rating_student_id=student.id
GROUP BY student.id
ORDER BY rating DESC

return render_to_response('site.html', {'student' : Student.objects.all().filter(rating__rating_student_id=Student.objects.all()).annotate(total=Count('id')).order_by('-rating__rating_lesson')})

{% for name in student %}
        <tr>
          <td>{{ name.student_name }}</td>
          <td>тут должна быть средняя оценка</td>
      </tr>
{% endfor %}

{% for name in student %}
        <tr>
          <td>{{ name.student_name }}</td>
          <td>{{ name.rating_set.rating_lesson }}</td>
      </tr>
{% endfor %}

{% for name in student %}
        <tr>
          <td>{{ name.student_name }}</td>
          <td>{% for ratings in name.rating_set.all %}
                     {{ ratings.rating_lesson }}
                 {% endfor %}
         </td>
      </tr>
{% endfor %}

from django.db import connection, transaction
    cursor = connection.cursor()
    cursor.execute('''SELECT student_name, ROUND(AVG(rating_lesson), 2) AS avg_rating FROM student
                    INNER JOIN rating ON rating.rating_student_id=student.id
                    GROUP BY student.id
                    ORDER BY avg_rating DESC''')
    out = []
    while(True):
        row = cursor.fetchone()
        if(row == None):
            break
        else:
            out.append(row)
    return render_to_response('site.html', {'student' : out})

while True:
        row = cursor.fetchone()
        if not row:
            break
        out.append(row)

out = [i for i in cursor.fetchone()]

Student.objects.values('student_name').aggregate(avg=Avg('rating__rating_lesson')).ordr_by('avg')