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我是 django 新手,正在创建模型,但在尝试将外键添加到另一个模型时遇到问题。这是我的模型:
from django.db import models
class User(models.Model):
user_id = models.CharField(max_length=10, primary_key=True)
name = models.CharField(max_length=30)
surname = models.CharField(max_length=30)
role = models.CharField(max_length=10)
address = models.CharField(max_length=50)
email = models.EmailField(max_length=30)
password = models.CharField(max_length=20)
phone = models.IntegerField()
GPA = models.FloatField(max_length=5)
Gender = models.CharField(max_length=1)
def __str__(self):
return self.user_id
class Login(models.Model):
user_id = models.ForeignKey(User, on_delete=models.CASCADE, default='00000')
email = models.EmailField(max_length=30)
password = models.CharField(max_length=20)
def __str__(self):
return self.email
当我输入 makemigrations 时,我得到:
You are trying to change the nullable field 'user_id' on login to non-nullable without a default; we can't do that (the database needs something to populate existing rows).
Please select a fix:
1) Provide a one-off default now (will be set on all existing rows)
2) Ignore for now, and let me handle existing rows with NULL myself (e.g. because you added a RunPython or RunSQL operation to handle NULL values in a previous data migration)
3) Quit, and let me add a default in models.py
Select an option: 3
所以我添加了默认值,但当我尝试迁移时收到此错误。我尝试将 user_id 从 User 更改为 AutoField,这样我就不必添加任何默认值,但它仍然给我这个错误。另外我不知道为什么它最后说 user_id_id 。谁能帮我解决这个问题吗?
Running migrations:
Rendering model states... DONE
Applying login.0003_login_user_id...Traceback (most recent call last):
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\mysql\base.py", line 112, in execute
return self.cursor.execute(query, args)
File "C:\User\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\cursors.py", line 226, in execute
self.errorhandler(self, exc, value)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\connections.py", line 42, in defaulterrorhandler
raise errorvalue
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\cursors.py", line 223, in execute
res = self._query(query)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\cursors.py", line 379, in _query
rowcount = self._do_query(q)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\cursors.py", line 342, in _do_query
db.query(q)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\connections.py", line 286, in query
_mysql.connection.query(self, query)
_mysql_exceptions.OperationalError: (1067, "Invalid default value for 'user_id_id'")
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "C:\Program Files (x86)\JetBrains\PyCharm 5.0.4\helpers\pycharm\django_manage.py", line 41, in <module>
run_module(manage_file, None, '__main__', True)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\runpy.py", line 182, in run_module
return _run_module_code(code, init_globals, run_name, mod_spec)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\runpy.py", line 96, in _run_module_code
mod_name, mod_spec, pkg_name, script_name)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\runpy.py", line 85, in _run_code
exec(code, run_globals)
File "C:/Users/Desktop/Project/TSL/mysite\manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\core\management\__init__.py", line 353, in execute_from_command_line
utility.execute()
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\core\management\__init__.py", line 345, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\core\management\base.py", line 348, in run_from_argv
self.execute(*args, **cmd_options)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\core\management\base.py", line 399, in execute
output = self.handle(*args, **options)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\core\management\commands\migrate.py", line 200, in handle
executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\migrations\executor.py", line 92, in migrate
self._migrate_all_forwards(plan, full_plan, fake=fake, fake_initial=fake_initial)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\migrations\executor.py", line 121, in _migrate_all_forwards
state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\migrations\executor.py", line 198, in apply_migration
state = migration.apply(state, schema_editor)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\migrations\migration.py", line 123, in apply
operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\migrations\operations\fields.py", line 62, in database_forwards
field,
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\mysql\schema.py", line 50, in add_field
super(DatabaseSchemaEditor, self).add_field(model, field)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\base\schema.py", line 396, in add_field
self.execute(sql, params)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\base\schema.py", line 110, in execute
cursor.execute(sql, params)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\utils.py", line 79, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\utils.py", line 95, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\utils\six.py", line 685, in reraise
raise value.with_traceback(tb)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\mysql\base.py", line 112, in execute
return self.cursor.execute(query, args)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\cursors.py", line 226, in execute
self.errorhandler(self, exc, value)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\connections.py", line 42, in defaulterrorhandler
raise errorvalue
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\cursors.py", line 223, in execute
res = self._query(query)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\cursors.py", line 379, in _query
rowcount = self._do_query(q)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\cursors.py", line 342, in _do_query
db.query(q)
File "C:\Users\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\connections.py", line 286, in query
_mysql.connection.query(self, query)
django.db.utils.OperationalError: (1067, "Invalid default value for 'user_id_id'")
Process finished with exit code 1
最佳答案
首先,正如评论中提到的,不要将 ForeignKey
字段命名为 user_id
,而命名为 user
。这将在数据库表中创建一个名为 user_id
的列,并且模型实例的 user
属性将返回一个 User
实例,而其自动生成的属性 user_id
将返回该用户的 ID。
至于指定 ForeignKey
的默认值。如果您在模型上执行此操作,请确保提供现有用户。如果您选择在 makemigrations
期间提供一次性默认值(如果您选择选项 1),请确保提供现有用户的主键。或者,确保数据库中没有现有的 Login
记录。
关于python - django 中 user_id_id 的默认值无效,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/35967330/
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