class Users(models.Model):
    name = models.CharField(max_length=255)
    email = models.CharField(max_length=255, blank=True)
    age = models.IntegerField()
    class Meta:
        db_table = u'users'
    def __unicode__(self):
        return u'%s' % (self.name)

SELECT `name`, count(`age`) FROM `users` GROUP BY `name`;

u = Users.objects.values('name').annotate(cnt=Count('age'))