在我的应用中，我的CalibrationForm模型中有一个名为cf_ani的字段
cf_ani = models.CharField(max_length=150)
我希望该字段成为一个下拉菜单，用户可以在其中选择称为Subjects的模型中的选项。因此，我将models.py中的字段从CharField更改为ForeignKey：
cf_ani = models.ForeignKey(
Subjects,
on_delete=models.CASCADE,
)
我运行python manage.py makemigrations并生成更改的字段。
我运行python manage.py migrate，并返回以下内容：
Running migrations:
Applying CalibrationForm.0026_auto_20180821_0630...Traceback (most recent call last):
File "/usr/local/lib/python3.4/dist-packages/django/db/backends/utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.4/dist-packages/django/db/backends/mysql/base.py", line 71, in execute
return self.cursor.execute(query, args)
File "/usr/local/lib/python3.4/dist-packages/MySQLdb/cursors.py", line 250, in execute
self.errorhandler(self, exc, value)
File "/usr/local/lib/python3.4/dist-packages/MySQLdb/connections.py", line 50, in defaulterrorhandler
raise errorvalue
File "/usr/local/lib/python3.4/dist-packages/MySQLdb/cursors.py", line 247, in execute
res = self._query(query)
File "/usr/local/lib/python3.4/dist-packages/MySQLdb/cursors.py", line 411, in _query
rowcount = self._do_query(q)
File "/usr/local/lib/python3.4/dist-packages/MySQLdb/cursors.py", line 374, in _do_query
db.query(q)
File "/usr/local/lib/python3.4/dist-packages/MySQLdb/connections.py", line 277, in query
_mysql.connection.query(self, query)
_mysql_exceptions.OperationalError: (1054, "Unknown column 'cf_ani' in 'CalibrationForm_calibrationform'")
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "manage.py", line 15, in <module>
execute_from_command_line(sys.argv)
File "/usr/local/lib/python3.4/dist-packages/django/core/management/__init__.py", line 371, in execute_from_command_line
utility.execute()
File "/usr/local/lib/python3.4/dist-packages/django/core/management/__init__.py", line 365, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/lib/python3.4/dist-packages/django/core/management/base.py", line 288, in run_from_argv
self.execute(*args, **cmd_options)
File "/usr/local/lib/python3.4/dist-packages/django/core/management/base.py", line 335, in execute
output = self.handle(*args, **options)
File "/usr/local/lib/python3.4/dist-packages/django/core/management/commands/migrate.py", line 200, in handle
fake_initial=fake_initial,
File "/usr/local/lib/python3.4/dist-packages/django/db/migrations/executor.py", line 117, in migrate
state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
File "/usr/local/lib/python3.4/dist-packages/django/db/migrations/executor.py", line 147, in _migrate_all_forwards
state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
File "/usr/local/lib/python3.4/dist-packages/django/db/migrations/executor.py", line 244, in apply_migration
state = migration.apply(state, schema_editor)
File "/usr/local/lib/python3.4/dist-packages/django/db/migrations/migration.py", line 122, in apply
operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
File "/usr/local/lib/python3.4/dist-packages/django/db/migrations/operations/fields.py", line 216, in database_forwards
schema_editor.alter_field(from_model, from_field, to_field)
File "/usr/local/lib/python3.4/dist-packages/django/db/backends/base/schema.py", line 509, in alter_field
old_db_params, new_db_params, strict)
File "/usr/local/lib/python3.4/dist-packages/django/db/backends/base/schema.py", line 592, in _alter_field
self.execute(self._rename_field_sql(model._meta.db_table, old_field, new_field, new_type))
File "/usr/local/lib/python3.4/dist-packages/django/db/backends/base/schema.py", line 117, in execute
cursor.execute(sql, params)
File "/usr/local/lib/python3.4/dist-packages/django/db/backends/utils.py", line 100, in execute
return super().execute(sql, params)
File "/usr/local/lib/python3.4/dist-packages/django/db/backends/utils.py", line 68, in execute
return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
File "/usr/local/lib/python3.4/dist-packages/django/db/backends/utils.py", line 77, in _execute_with_wrappers
return executor(sql, params, many, context)
File "/usr/local/lib/python3.4/dist-packages/django/db/backends/utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.4/dist-packages/django/db/utils.py", line 89, in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
File "/usr/local/lib/python3.4/dist-packages/django/db/backends/utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.4/dist-packages/django/db/backends/mysql/base.py", line 71, in execute
return self.cursor.execute(query, args)
File "/usr/local/lib/python3.4/dist-packages/MySQLdb/cursors.py", line 250, in execute
self.errorhandler(self, exc, value)
File "/usr/local/lib/python3.4/dist-packages/MySQLdb/connections.py", line 50, in defaulterrorhandler
raise errorvalue
File "/usr/local/lib/python3.4/dist-packages/MySQLdb/cursors.py", line 247, in execute
res = self._query(query)
File "/usr/local/lib/python3.4/dist-packages/MySQLdb/cursors.py", line 411, in _query
rowcount = self._do_query(q)
File "/usr/local/lib/python3.4/dist-packages/MySQLdb/cursors.py", line 374, in _do_query
db.query(q)
File "/usr/local/lib/python3.4/dist-packages/MySQLdb/connections.py", line 277, in query
_mysql.connection.query(self, query)
django.db.utils.OperationalError: (1054, "Unknown column 'cf_ani' in 'CalibrationForm_calibrationform'")
由于此更改，我什至无法返回CharField类型或产生相同的异常。我可以回到以前的迁移，但是对该模型进行任何进一步的更改都是不可能的。是什么原因导致这种情况发生？我读到Django在幕后将“ _id”附加到列名。是因为在某些地方而不是cf_ani引用了cf_ani_id导致了我的例外？如果是这样，难道不会恢复为CharField来解决该问题吗？
是否有替代方法可以使用ForeignKey来避免此问题？