Solution of database migration error

When changing model classes ：
When you need to change the model class
Delete tables and... In the database migrations Migration files in
Re migrate
Execute first

python manage.py makemigrations

Information after execution

-Create model User

Re execution python manage.py migrate You're going to report a mistake

No migrations to apply

When we are migrating files
A total of three party files will be generated , The migration file 、 Tables in the database and records of migration information
Here is an example of a project I wrote before
We open the database

Migration open django_migrations Table will see the previous migration records

Because of this user The migration record database will think that we have completed the migration and will not be migrating
Execute again after deletion python manage.py migrate You can successfully migrate
Finally remember ：
The migration file 、 Tables in the database and records of migration information are indispensable when deleting , The absence of any party will report an error .