Django 模型(1054，Unknown column in 'field list')

不知道为什么会出现这个错误.以下是我创建的模型-

from django.db import models
from django.contrib.auth.models import User

class Shows(models.Model):
    showid= models.CharField(max_length=10, unique=True, db_index=True)
    name  = models.CharField(max_length=256, db_index=True)
    aka   = models.CharField(max_length=256, db_index=True)
    score = models.FloatField()

class UserShow(models.Model):
    user  = models.ForeignKey(User)
    show  = models.ForeignKey(Shows)

这是我访问这些模型的视图-

from django.http import HttpResponse
from django.template import Context
from django.template.loader import get_template
from django.http import HttpResponse, Http404
from django.contrib.auth.models import User

def user_page(request, username):
    try:
        user = User.objects.get(username=username)
    except:
        raise Http404('Requested user not found.')

    shows     = user.usershow_set.all()
    template  = get_template('user_page.html')
    variables = Context({
        'username': username,
        'shows'   : shows})
    output = template.render(variables)
    return HttpResponse(output)

在这一点上，我得到了一个错误-

OperationalError: (1054, "Unknown column 'appname_usershow.show_id' in 'field list'")个

如你所见，我的模特中甚至都没有这个栏目？为什么会出现这个错误？