“字段列表”中的未知列“”。 姜戈

Question

我正在使用 Django 1.9 和 MySQL。 我想重命名模型中的一个字段。 让我们看看Django 入门教程中的模型Choice 。

class Choice(models.Model):
  question = models.ForeignKey(Question)
  choice_text = models.CharField(max_length = 200)
  votes = models.IntegerField(default=0)

所以，我想将votes字段重命名为votes_count 。 我创建了一个空迁移并添加到以下行的操作中：

migrations.RenameField (
    model_name='choice',
    old_name='votes',
    new_name='votes_count',
),

在python manage.py migrate ，数据库表中的字段被重命名。 但是当我尝试使用这个模型时

def vote(request, question_id):
  question = get_object_or_404(Question, pk=question_id);
  try:
    selected = question.choice_set.get(pk=request.POST['choice'])
  except (KeyError, Choice.DoesNotExist):
    return render(request, 'polls/detail.html', {
      'question':question,
      'error_message':"You didn't select a choice."
    })
  else:
    selected.votes_count += 1
    selected.save()
    return HttpResponseRedirect(reverse('polls:results', args=(question_id)))

我有：

“字段列表”中的未知列“polls_choice.votes”

    Traceback:

    File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/utils.py" in execute
      64.                 return self.cursor.execute(sql, params)

    File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/mysql/base.py" in execute
      112.             return self.cursor.execute(query, args)

    File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in execute
      226.             self.errorhandler(self, exc, value)

    File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/connections.py" in defaulterrorhandler
      36.         raise errorvalue

    File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in execute
      217.             res = self._query(query)

    File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in
_query
      378.         rowcount = self._do_query(q)

    File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in
_do_query
      341.         db.query(q)

    File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/connections.py" in query
      280.             _mysql.connection.query(self, query)

    The above exception ((1054, "Unknown column 'polls_choice.votes' in 'field list'")) was the direct cause of the following exception:

    File "/home/verdigo/venv/lib/python3.4/site-packages/django/core/handlers/base.py" in get_response
      149.                     response = self.process_exception_by_middleware(e, request)

    File "/home/verdigo/venv/lib/python3.4/site-packages/django/core/handlers/base.py" in get_response
      147.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)

    File "./polls/views.py" in vote
      23.     selected = question.choice_set.get(pk=request.POST['choice'])

    File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/manager.py" in manager_method
      122.                 return getattr(self.get_queryset(), name)(*args, **kwargs)

    File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/query.py" in get
      381.         num = len(clone)

    File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/query.py" in __len__
      240.         self._fetch_all()

    File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/query.py" in _fetch_all
      1074.             self._result_cache = list(self.iterator())

    File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/query.py" in __iter__
      52.         results = compiler.execute_sql()

    File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/sql/compiler.py" in execute_sql
      848.             cursor.execute(sql, params)

    File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/utils.py" in execute
      79.             return super(CursorDebugWrapper, self).execute(sql, params)

    File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/utils.py" in execute
      64.                 return self.cursor.execute(sql, params)

    File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/utils.py" in
__exit__
      95.                 six.reraise(dj_exc_type, dj_exc_value, traceback)

    File "/home/verdigo/venv/lib/python3.4/site-packages/django/utils/six.py" in reraise
      685.             raise value.with_traceback(tb)

    File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/utils.py" in execute
      64.                 return self.cursor.execute(sql, params)

    File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/mysql/base.py" in execute
      112.             return self.cursor.execute(query, args)

    File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in execute
      226.             self.errorhandler(self, exc, value)

    File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/connections.py" in defaulterrorhandler
      36.         raise errorvalue

    File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in execute
      217.             res = self._query(query)

    File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in
_query
      378.         rowcount = self._do_query(q)

    File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in
_do_query
      341.         db.query(q)

    File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/connections.py" in query
      280.             _mysql.connection.query(self, query)

    Exception Type: OperationalError at /polls/1/vote/
    Exception Value: (1054, "Unknown column 'polls_choice.votes' in 'field list'")

Answer 1

看起来好像您创建并运行了迁移以将模型字段从votes重命名为votes_count ，但没有同时更新模型。

当 Django 尝试从数据库中获取模型时，它会尝试选择votes列，因为您的模型中仍然有一个 votes 字段，并且您收到错误，因为该列在数据库中不存在。

通常不需要创建手动迁移。 通常，您会重命名模型字段，运行makemigrations ，然后运行migrate 。 让 Django 创建迁移的优势在于，您可以确信在运行 migrate 后数据库与您的模型同步。

Answer 2

这是一个一直困扰着我的问题，并让我陷入了很多删除表等的兔子洞。我发现的一个简单的解决方案是当 django 询问您是否要重命名该模型的字段时（运行 makemigrations 时）回答“N” ）。 然后基本上执行的是删除您之前的字段并创建新字段。 请小心，因为您可能会丢失现有字段上的数据，因此这适用于新字段或相对容易“重新填充”所需数据的字段。 如果您在 makemigrations 后迁移时遇到无法“删除字段”的错误，则可能需要运行 --fake。

更新：我对布尔字段执行了上述操作，并保留了我的数据。 尽管我说的是 N，但它似乎本质上是一种重命名。

Answer 3

原因：新建一对多外键时出现此错误，指向带有forkey字段的模型，然后生成表

.

解决方法：直接删除数据库，重建即可解决此问题。

1：删除数据库数据库表；

2、删除后重新创建，创建之前的代码，直接运行