Create a Model in Django app and manage migrations

Working with databases in Django involves working with models. A model contains the fields and behaviors of the data we want to store.

Commonly, each model maps to a database table, and field in a model maps to table column.

Here are the Django model basics:

• Each model is a class that extends django.db.models.Model
• Each model property represents a database column.
• Django provides us with a set of useful methods to CRUD model information from a database.

Create model

Each app has the models.py file, we create model in this file, for example:

from djang.db import models

class Movie(models.Model):
	title = models.CharField(max_length=100)
	description = models.CharField(max_length=255)
	image = models.ImageField(upload_to='movie/images/')
	url = models.URLField(blank=True)

class Movie inherits from Model class, which allows us to interact with the database, create a table, and retrieve and make changes to data in the database.

Django provides many model fields to support common types such as CharField, ImageField, URLField.

Manage migrations

Migrations allows us to generate a database schema based on model code. Once we make changes to our models(such as adding a field, renaming a field), new migrations should be created.

In the end, migrations allow us to have a trace of the evolution of our database schema(as a version control system).

After model changing, run makemigrations command to generate the SQL commands for the defined models in all preinstalled apps in the INSTALLED_APPS setting. The SQL commands are not yet executed but are just a record of all changes to our models. The migrations are stored in an auto-generated folder migrations/ under the app folder.

$ python manage.py makemigrations [appname]

To actually execute the SQL commands in the migrations file, run:

$ python manage.py migrate [appname]