为什么我的数据库抛出一个错误？

Question

我试图通过管理网站访问我的应用程序，而这样做Django的教程，并正在此错误：

DatabaseError at /admin/polls/poll/ (1054, "Unknown column 'polls_poll.question' in 'field list'") 

本来我把我的模型使用问题类，而错误地使用1.6版本的该教程，但切换到1.54版本，并不得不重新命名我的问题类为民意调查。然后我重新启动了数据库。我正在使用MySQL。

现在，每次我从管理网站点击“投票”它会引发上述错误。

我试图冲洗我的数据库和resyncing，但没有奏效。

这里是我的models.py代码：

from django.db import models 
import datetime 
from django.utils import timezone 

class Poll(models.Model): 
    question = models.CharField(max_length=200) 
    pub_date = models.DateTimeField('date published') 

    def __unicode__(self): 
     return self.question 

    def was_published_recently(self): 
     return self.pub_date >= timezone.now() - datetime.timedelta(days=1) 

class Choice(models.Model): 

    poll = models.ForeignKey(Poll) 
    choice_text = models.CharField(max_length=200) 
    votes = models.IntegerField(default=0) 

    def __unicode__(self): 
     return self.choice_text 

以下是完整回溯：

Internal Server Error: /admin/polls/poll/ 
Traceback (most recent call last): 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/django/core/handlers/base.py", line 115, in get_response 
    response = callback(request, *callback_args, **callback_kwargs) 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/django/contrib/admin/options.py", line 372, in wrapper 
    return self.admin_site.admin_view(view)(*args, **kwargs) 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/django/utils/decorators.py", line 91, in _wrapped_view 
    response = view_func(request, *args, **kwargs) 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/django/views/decorators/cache.py", line 89, in _wrapped_view_func 
    response = view_func(request, *args, **kwargs) 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/django/contrib/admin/sites.py", line 202, in inner 
    return view(request, *args, **kwargs) 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/django/utils/decorators.py", line 25, in _wrapper 
    return bound_func(*args, **kwargs) 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/django/utils/decorators.py", line 91, in _wrapped_view 
    response = view_func(request, *args, **kwargs) 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/django/utils/decorators.py", line 21, in bound_func 
    return func(self, *args2, **kwargs2) 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/django/contrib/admin/options.py", line 1285, in changelist_view 
    'selection_note': _('0 of %(cnt)s selected') % {'cnt': len(cl.result_list)}, 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/django/db/models/query.py", line 106, in __len__ 
    self._result_cache = list(self.iterator()) 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/django/db/models/query.py", line 317, in iterator 
    for row in compiler.results_iter(): 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 775, in results_iter 
    for rows in self.execute_sql(MULTI): 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 840, in execute_sql 
    cursor.execute(sql, params) 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/django/db/backends/util.py", line 41, in execute 
    return self.cursor.execute(sql, params) 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/django/db/backends/mysql/base.py", line 128, in execute 
    six.reraise(utils.DatabaseError, utils.DatabaseError(*tuple(e.args)), sys.exc_info()[2]) 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/django/db/backends/mysql/base.py", line 120, in execute 
    return self.cursor.execute(query, args) 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/MySQLdb/cursors.py", line 201, in execute 
    self.errorhandler(self, exc, value) 
    File "/Users/MyClean/anaconda/lib/python2.7/site-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler 
    raise errorclass, errorvalue 
DatabaseError: (1054, "Unknown column 'polls_poll.question' in 'field list'") 

Answer 1

Django的syncdb命令只创建一个已经不存在的表。因此，如果您以前使用不同版本的模型同步数据库，则字段名称中的任何更改都不会出现在数据库表中。

要验证，请使用mysql客户端检查您的polls_poll表。

mysql> DESCRIBE polls_poll; 

您可能会看到question字段丢失。

正如评论中所建议的那样，您可以擦除整个数据库，但是一种侵入性较小的解决方案只需要删除polls_poll表并再次运行syncdb。

mysql> DROP TABLE polls_poll; 
$ manage.py syncdb 

这当然会删除所有与民意调查相关的数据。