Django：1215，“无法在只有一个字段的模型上添加外键约束”

Posted 2023-02-24

【中文标题】Django：1215，“无法在只有一个字段的模型上添加外键约束”

【英文标题】：Django: 1215, 'Cannot add foreign key constraint' on model with only one field

【发布时间】：2019-01-01 10:34:38

【问题描述】：

我有一个Salad 模型：

class Salad(models.Model):
    some_field = models.ForeignKey(Profile, on_delete=models.CASCADE, null=True)

无论我如何调用类、单个字段、我放置什么模型而不是 Profile，或者我选择的任何 on_delete 选项。我系统地得到了错误：

django.db.utils.IntegrityError: (1215, 'Cannot add foreign key constraint')

错误日志：

Traceback (most recent call last):
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\utils.py", line 85, in _execute
  Applying playerdata.0053_auto_20180724_1943...    return self.cursor.execute(sql, params)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\mysql\base.py", line 71, in execute
    return self.cursor.execute(query, args)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\cursors.py", line 250, in execute
    self.errorhandler(self, exc, value)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\connections.py", line 50, in defaulterrorhandler
    raise errorvalue
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\cursors.py", line 247, in execute
    res = self._query(query)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\cursors.py", line 411, in _query
    rowcount = self._do_query(q)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\cursors.py", line 374, in _do_query
    db.query(q)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\connections.py", line 292, in query
    _mysql.connection.query(self, query)
_mysql_exceptions.IntegrityError: (1215, 'Cannot add foreign key constraint')

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "C:\Program Files\JetBrains\PyCharm 2017.3.2\helpers\pycharm\django_manage.py", line 52, in <module>
    run_command()
  File "C:\Program Files\JetBrains\PyCharm 2017.3.2\helpers\pycharm\django_manage.py", line 46, in run_command
    run_module(manage_file, None, '__main__', True)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\runpy.py", line 205, in run_module
    return _run_module_code(code, init_globals, run_name, mod_spec)
  File "C:\Users\Div-o\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\Div-o\AppData\Local\Programs\Python\Python35-32\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "E:/Python/DjangoProjects/rolegate\manage.py", line 15, in <module>
    execute_from_command_line(sys.argv)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\core\management\__init__.py", line 371, in execute_from_command_line
    utility.execute()
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\core\management\__init__.py", line 365, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\core\management\base.py", line 288, in run_from_argv
    self.execute(*args, **cmd_options)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\core\management\base.py", line 335, in execute
    output = self.handle(*args, **options)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\core\management\commands\migrate.py", line 200, in handle
    fake_initial=fake_initial,
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-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 "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-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 "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\migrations\executor.py", line 244, in apply_migration
    state = migration.apply(state, schema_editor)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\base\schema.py", line 90, in __exit__
    self.execute(sql)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\base\schema.py", line 117, in execute
    cursor.execute(sql, params)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\utils.py", line 100, in execute
    return super().execute(sql, params)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\utils.py", line 68, in execute
    return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\utils.py", line 77, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\utils.py", line 85, in _execute
    return self.cursor.execute(sql, params)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\utils.py", line 89, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\utils.py", line 85, in _execute
    return self.cursor.execute(sql, params)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\mysql\base.py", line 71, in execute
    return self.cursor.execute(query, args)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\cursors.py", line 250, in execute
    self.errorhandler(self, exc, value)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\connections.py", line 50, in defaulterrorhandler
    raise errorvalue
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\cursors.py", line 247, in execute
    res = self._query(query)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\cursors.py", line 411, in _query
    rowcount = self._do_query(q)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\cursors.py", line 374, in _do_query
    db.query(q)
  File "C:\Users\Div-o\AppData\Local\Programs\Python\Python35-32\lib\site-packages\MySQLdb\connections.py", line 292, in query
    _mysql.connection.query(self, query)
django.db.utils.IntegrityError: (1215, 'Cannot add foreign key constraint')

【问题讨论】：

你在使用MyISAM引擎吗？

我不知道那是什么所以我想我不是。

等等，我在 mysql workbench 中看到新模型是使用 InnoDB 创建的，但其他所有模型确实是使用 myISAM 的！知道我在本地使用从生产服务器导入的数据库

【参考方案1】：

通常这是由于您的两个相关表没有使用 InnoDB 并且其中至少有一个使用了 MyISAM 引擎。

问题是Foreign keys are not supported on MyISAM。

这是一个相关的 Django 票证#26777。

由于这完全与 MYSQL 相关，而不是特定于 Django，我将链接这个可能对您有潜在帮助的线程，

Converting Tables from MyISAM to InnoDB

花絮

即使名字相似，我也不是处理这张 Django 票的人。 @SimonCharette 是。