关键步骤：
- 第一步： 执行：python manage.py makemigrations 你的项目名称
- 第二步：它会提示你选1还是2，这里因为添加字段，所以选1
- 第三步：出现>>>这个，直接输入这个''
- 第四步： 执行：python manage.py migrate
- 第五步：运行项目：python manage.py runserver 本机ip:8000
(.venv) PS D:\python_workpace\django_xitong_shezhi\pythonProject\myproject> python manage.py makemigrations myproject
It is impossible to add a non-nullable field 'title_field22' to yingyongguanli without specifying a default. This is because the database needs something to populate existing rows.
Please select a fix:2) Quit and manually define a default value in models.py.
Select an option: 1
Please enter the default value as valid Python.
The datetime and django.utils.timezone modules are available, so it is possible to provide e.g. timezone.now as a value.
>>> ‘’
Invalid input: invalid character '‘' (U+2018) (<string>, line 1)
>>> ''
Migrations for 'myproject':myproject\migrations\0002_yingyongguanli_title_field22.py- Add field title_field22 to yingyongguanli
(.venv) PS D:\python_workpace\django_xitong_shezhi\pythonProject\myproject> python manage.py migrate
Operations to perform:Apply all migrations: admin, auth, contenttypes, myproject, sessions
Running migrations:Applying myproject.0002_yingyongguanli_title_field22... OK
(.venv) PS D:\python_workpace\django_xitong_shezhi\pythonProject\myproject> python manage.py runserver 10.0.4.144:8000
Watching for file changes with StatReloader
Performing system checks...System check identified no issues (0 silenced).
August 07, 2024 - 15:05:12
Django version 5.0.6, using settings 'myproject.settings'
Starting development server at http://10.0.4.144:8000/
Quit the server with CTRL-BREAK.
