数据库升级成sqlserver2019后，用户发现一些APP不能用了，检查发现是Django连接sqlserver的APP全部不能用了，页面打开都是500错误，进入Pycharm调试发现：
1.遇到错误1：django.db.backends.XXX'错误
File "C:\Python\Python310\lib\site-packages\django\db\utils.py", line 202, in getitem
backend = load_backend(db'ENGINE')
File "C:\Python\Python310\lib\site-packages\django\db\utils.py", line 121, in load_backend
raise ImproperlyConfigured(
django.core.exceptions.ImproperlyConfigured: 'sql_server.pyodbc' isn't an available database backend.
Try using 'django.db.backends.XXX', where XXX is one of:
'mysql', 'oracle', 'postgresql', 'sqlite3'
按网上提示，修改连接字符串是绝对不好使的，安装相关的库也不好使。
C:\Users\Administrator>pip install django-mssql-backend
Collecting django-mssql-backend
Downloading django_mssql_backend-2.8.1-py3-none-any.whl.metadata (7.4 kB)
Requirement already satisfied: pyodbc>=3.0 in c:\python\python310\lib\site-packages (from django-mssql-backend) (4.0.32)
Downloading django_mssql_backend-2.8.1-py3-none-any.whl (52 kB)
---------------------------------------- 52.4/52.4 kB 669.1 kB/s eta 0:00:00
Installing collected packages: django-mssql-backend
Successfully installed django-mssql-backend-2.8.1
notice A new release of pip is available: 23.3.2 -> 25.0.1
notice To update, run: python.exe -m pip install --upgrade pip
C:\Users\Administrator>pip install django-pyodbc-azure
Requirement already satisfied: django-pyodbc-azure in c:\python\python310\lib\site-packages (2.1.0.0)
Requirement already satisfied: Django<2.2,>=2.1.0 in c:\python\python310\lib\site-packages (from django-pyodbc-azure) (2.1.15)
Requirement already satisfied: pyodbc>=3.0 in c:\python\python310\lib\site-packages (from django-pyodbc-azure) (4.0.32)
Requirement already satisfied: pytz in c:\python\python310\lib\site-packages (from Django<2.2,>=2.1.0->django-pyodbc-azure) (2022.1)
notice A new release of pip is available: 23.3.2 -> 25.0.1
notice To update, run: python.exe -m pip install --upgrade pip
C:\Users\Administrator>python
>>> import django
>>> print(django.get_version())
2.1.15
解决方案：必须要升级Django才能解决问题
C:\Users\Administrator>pip install --upgrade django==3.2.0
Collecting django==3.2.0
Using cached Django-3.2-py3-none-any.whl.metadata (3.9 kB)
Requirement already satisfied: asgiref<4,>=3.3.2 in c:\python\python310\lib\site-packages (from django==3.2.0) (3.8.1)
Requirement already satisfied: pytz in c:\python\python310\lib\site-packages (from django==3.2.0) (2022.1)
Requirement already satisfied: sqlparse>=0.2.2 in c:\python\python310\lib\site-packages (from django==3.2.0) (0.4.2)
Requirement already satisfied: typing-extensions>=4 in c:\python\python310\lib\site-packages (from asgiref<4,>=3.3.2->django==3.2.0) (4.5.0)
Using cached Django-3.2-py3-none-any.whl (7.9 MB)
Installing collected packages: django
Attempting uninstall: django
Found existing installation: Django 2.1.3
Uninstalling Django-2.1.3:
Successfully uninstalled Django-2.1.3
ERROR: pip's dependency resolver does not currently take into account all the packages that are installed. This behaviour is the source of the following dependency conflicts.
django-pyodbc-azure 2.1.0.0 requires Django<2.2,>=2.1.0, but you have django 3.2 which is incompatible.
Successfully installed django-3.2
C:\Users\Administrator>pip install --upgrade requests
Requirement already satisfied: requests in c:\python\python310\lib\site-packages (2.27.1)
Collecting requests
Downloading requests-2.32.3-py3-none-any.whl.metadata (4.6 kB)
Requirement already satisfied: charset-normalizer<4,>=2 in c:\python\python310\lib\site-packages (from requests) (2.0.12)
Requirement already satisfied: idna<4,>=2.5 in c:\python\python310\lib\site-packages (from requests) (3.3)
Requirement already satisfied: urllib3<3,>=1.21.1 in c:\python\python310\lib\site-packages (from requests) (1.26.9)
Requirement already satisfied: certifi>=2017.4.17 in c:\python\python310\lib\site-packages (from requests) (2021.10.8)
Downloading requests-2.32.3-py3-none-any.whl (64 kB)
Installing collected packages: requests
Attempting uninstall: requests
Found existing installation: requests 2.27.1
Uninstalling requests-2.27.1:
Successfully uninstalled requests-2.27.1
Successfully installed requests-2.32.3
notice A new release of pip is available: 23.3.2 -> 25.0.1
notice To update, run: python.exe -m pip install --upgrade pip
C:\Users\Administrator>python.exe -m pip install --upgrade pip
Requirement already satisfied: pip in c:\python\python310\lib\site-packages (23.3.2)
Collecting pip
Downloading pip-25.0.1-py3-none-any.whl.metadata (3.7 kB)
Downloading pip-25.0.1-py3-none-any.whl (1.8 MB)
---------------------------------------- 1.8/1.8 MB 6.9 MB/s eta 0:00:00
Installing collected packages: pip
Attempting uninstall: pip
Found existing installation: pip 23.3.2
Uninstalling pip-23.3.2:
Successfully uninstalled pip-23.3.2
Successfully installed pip-25.0.1
2.遇到的错误2：升级django后，访问APP的时候，不再提示sqlserver连接错误了，但出新错误：
RequestsDependencyWarning: urllib3 (1.26.9) or chardet (5.1.0)/charset_normalizer (2.0.12) doesn't match a supported version!
warnings.warn("urllib3 ({}) or chardet ({})/charset_normalizer ({}) doesn't match a supported "
System check identified some issues:
更新 urllib3
C:\Users\Administrator>pip install --upgrade urllib3
Requirement already satisfied: urllib3 in c:\python\python310\lib\site-packages (1.26.9)
Collecting urllib3
Downloading urllib3-2.3.0-py3-none-any.whl.metadata (6.5 kB)
Downloading urllib3-2.3.0-py3-none-any.whl (128 kB)
Installing collected packages: urllib3
Attempting uninstall: urllib3
Found existing installation: urllib3 1.26.9
Uninstalling urllib3-1.26.9:
Successfully uninstalled urllib3-1.26.9
Successfully installed urllib3-2.3.0
3.遇到的错误3：
from django.shortcuts import HttpResponseRedirect,Http404,HttpResponse,render_to_response
ImportError: cannot import name 'render_to_response' from 'django.shortcuts' (C:\Python\Python310\lib\site-packages\django\shortcuts.py)
这个需要使用 render 代替 render_to_response。render_to_response已经被废弃
render 方法可接收三个参数，一是request参数，二是待渲染的html模板文件，三是保存具体数据的字典参数。它的作用就是将数据填充进模板文件，最后把结果返回给浏览器。
4.遇到的错误4：
?: (corsheaders.E013) Origin '*' in CORS_ORIGIN_WHITELIST is missing scheme or netloc
HINT: Add a scheme (e.g. https://) or netloc (e.g. example.com).
CORS_ORIGIN_WHITELIST = (
'http://127.0.0.1:\*'
)
将原来的值'http://127.0.0.1','http://192.168.0.1'改成'http://127.0.0.1','http://192.168.0.1',通过
5.遇到新错误5：
django.core.exceptions.ImproperlyConfigured: WSGI application 'waitress.server:call_in_application' could not be loaded; Error importing module .
因为使用的是IIS,没有使用waitress, 直接用#注释掉
运行不正常的APP终于能正常运行。