我正在使用Django 1.9和MySQL。我想在模型中重命名一个字段。让我们看看Django getting started tutorial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)
因此，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：
migrations.RenameField (
model_name='choice',
old_name='votes',
new_name='votes_count',
),
在python manage.py migrate之后，重命名了数据库表中的字段。但是当我试图使用这个模型时
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)))
我得到了：
未知栏＆＃39; polls_choice.votes＆＃39;在＆＃39;字段列表
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'")
答案 0 :(得分：2)
您好像已创建并运行迁移，将模型字段从votes重命名为votes_count，但未同时更新模型。
当Django尝试从数据库中获取模型时，它会尝试选择votes列，因为您的模型中仍有一个投票字段，并且您收到错误，因为该列没有存在于数据库中。
通常不需要创建手动迁移。通常，您需要重命名模型字段，运行makemigrations，然后运行migrate。让Django创建迁移的好处是，您可以确信在运行迁移后数据库与模型同步。
答案 1 :(得分：1)
这是一个一直困扰着我的问题，导致我丢了很多兔子掉落的桌子等。当django询问您是否要重命名该模型的字段时，我发现一个简单的解决方案是回答“ N”（运行makemigrations时）。然后，基本上执行的操作是删除先前的字段并创建新的字段。请注意，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。如果在进行makemigrations后进行迁移时遇到无法“丢弃字段”的错误，则可能需要运行--fake。
更新： 我对布尔值字段进行了上述操作，并保留了我的数据。即使我说了N，也似乎本质上是在重命名。
答案 2 :(得分：0)
原因：新建一对多外键，指向带有forkey字段的模型，然后生成表时出现此错误
.
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，代码创建前，直接运行