不存在的变量的完整性错误

Question

  

（django.db.utils.IntegrityError：唯一约束失败：items_purchase.item_id）

这是我尝试迁移名为“ items”的应用程序时遇到的错误。

app name = items
model name = Purchase

我不明白什么是item_id。

class Purchase(models.Model): 
    name=models.CharField(max_length=200) 
    phone=models.IntegerField(default=0) 
    email=models.EmailField() 
    address=models.CharField(max_length=200) 
    pin=models.IntegerField(default='0') 
    state=models.CharField(max_length=200)


class Item(models.Model): 
    name=models.CharField(max_length=200) 
    c=models.ForeignKey(Category, on_delete=models.CASCADE) 
    photo=models.ImageField(default='0') 

    def __str__(self): 
        return 'Item: {}'.format(self.name)


def confirm(request): 
    f=PurchaseForm(request.POST) 
    if f.is_valid(): 
        name = f.cleaned_data['name'] 
        phone = f.cleaned_data['phone'] 
        email = f.cleaned_data['email'] 
        address = f.cleaned_data['address'] 
        pin = f.cleaned_data['pin'] 
        state = f.cleaned_data['state'] 
        f.save() 
        template=loader.get_template('items/confirm.html') 
        context={'f':f} 
        return HttpResponse(template.render(context,request))