为什么我在Django中不断收到“ _id不存在”错误？

Question

我不断收到column qanda_question.category_id does not exist错误。让我告诉你我的模型。

class QuestionCategory(models.Model):
    category = models.CharField(max_length=20, default="", primary_key = True)

    def __str__(self):
        return(str(self.category))

class Question(models.Model):
    number = models.IntegerField(primary_key=True)
    question = models.CharField(max_length=1000, default="")
    category = models.ForeignKey(QuestionCategory, on_delete=models.CASCADE, null=True, default=None)

    def __str__(self):
        return (str(self.category)+" "+str(self.number)+". "+str(self.title))

我尝试删除migrations文件夹中init.py文件夹中的所有迁移文件，但错误仍然存​​在。您认为出了什么问题？

+++仅供参考，models.py所在的目录为qanda。

+++完整追溯：
< / p>

Traceback (most recent call last):
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/db/backends/utils.py", line 86, in _execute
    return self.cursor.execute(sql, params)

The above exception (column qanda_question.category_id does not exist
LINE 1: ...a_question"."title", "qanda_question"."question", "qanda_que...
                                                             ^
) was the direct cause of the following exception:
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/core/handlers/base.py", line 115, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/core/handlers/base.py", line 113, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/contrib/admin/options.py", line 607, in wrapper
    return self.admin_site.admin_view(view)(*args, **kwargs)
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/utils/decorators.py", line 130, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/views/decorators/cache.py", line 44, in _wrapped_view_func
    response = view_func(request, *args, **kwargs)
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/contrib/admin/sites.py", line 231, in inner
    return view(request, *args, **kwargs)
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/utils/decorators.py", line 43, in _wrapper
    return bound_method(*args, **kwargs)
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/utils/decorators.py", line 130, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/contrib/admin/options.py", line 1796, in changelist_view
    'selection_note': _('0 of %(cnt)s selected') % {'cnt': len(cl.result_list)},
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/db/models/query.py", line 258, in __len__
    self._fetch_all()
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/db/models/query.py", line 1261, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/db/models/query.py", line 57, in __iter__
    results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/db/models/sql/compiler.py", line 1152, in execute_sql
    cursor.execute(sql, params)
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/db/backends/utils.py", line 100, in execute
    return super().execute(sql, params)
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/db/backends/utils.py", line 68, in execute
    return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/db/backends/utils.py", line 77, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/db/backends/utils.py", line 86, in _execute
    return self.cursor.execute(sql, params)
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/db/utils.py", line 90, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/home/ubuntu/myvenv/lib/python3.6/site-packages/django/db/backends/utils.py", line 86, in _execute
    return self.cursor.execute(sql, params)

Exception Type: ProgrammingError at /admin/qanda/question/
Exception Value: column qanda_question.category_id does not exist
LINE 1: ...a_question"."title", "qanda_question"."question", "qanda_que...