Code-Memo

Model Migrations

When you make changes in your models, these changes are not reflected to the database. When you make migrations, it reflects these changes, ensuring that the database structure get alongside the Django application without manual intervention or data loss.

Generating Migrations

To create a migration for model changes, use the makemigrations command, which analyzes your models and creates migration files that describe the changes to be applied to your database.

Suppose you have a Product model and decide to add a new field description:

1. Define the new field in your model:

   class Product(models.Model):
       name = models.CharField(max_length=100)
       price = models.DecimalField(max_digits=10, decimal_places=2)
       description = models.TextField()
   

2. Generate a migration for the new field:

   python manage.py makemigrations
   

   This command generates a migration file in your app’s migrations directory.

Applying Migrations

Once migrations are generated, use the migrate command to apply them to your database. This command runs through all the migrations and updates the database schema to match the current state of your models.

To apply the migration created in the previous step:

1. Apply migrations to the database:

   python manage.py migrate
   

   Django applies the new migration, creating or altering the description field in the Product table.