Using multiple databases with Django is feasible and sometimes necessary depending on the type of project you are handling. Django allows you to use any number of databases and to switch between them for your operations. Its database router controls the switching between databases.
The first step to use multiple databases involves defining the DATABASES setting in your Django settings file. This setting is a dictionary whose keys are the alias names given to each database, and the values are dictionary configurations for each database.
Here is an example:
```
DATABASES = {
‘default’: {
‘NAME’: ‘app_data’,
‘ENGINE’: ‘django.db.backends.postgresql’,
‘USER’: ‘postgres_user’,
‘PASSWORD’: ‘s3krit‘
},
‘users’: {
‘NAME’: ‘user_data’,
‘ENGINE’: ‘django.db.backends.mysql’,
‘USER’: ‘mysql_user’,
‘PASSWORD’: ‘priv4te‘
}
}
```
In the example above, we have two databases. The ‘default’ database is a PostgreSQL database for the application data, and ‘users’ is a MySQL database for user data.
If you want to perform an operation on a particular database, you can use the “using” keyword. Here is an example:
```
User.objects.using(‘users’).all()
```
In the example above, the database router is told to perform ‘User’ object-related operations using the ‘users’ database.
If you want to fully control the database routing in your Django application, you can define a database router. A database router is a class that provides four methods: `db_for_read()`, `db_for_write()`, `allow_relation()`, `allow_migrate()`.
Here is a simple example of a database router:
```
class AuthRouter:
def db_for_read(self, model, **hints):
if model._meta.app_label == ‘auth’:
return ‘users‘
return ‘default’
In this example, the router directs all READ and WRITE operations for Django’s built-in ‘auth’ app to the ‘users’ database, else the ‘default’ database is used.
You can define as many routers as you want and add them to the DATABASE\_ROUTERS setting of your Django project:
```
DATABASE_ROUTERS = [‘path.to.AuthRouter’]
```
And that’s how to use multiple databases with Django. You can find more information in the Django documentation’s database section (https://docs.djangoproject.com/en/4.0/topics/db/multi-db/).
Routers can also be used to conditionally allow database relations and database migrations.
The DATABASES setting is a dictionary containing the configuration for all databases to be used with Django. It is a required Django setting.
Remember to install the required database drivers needed by Django for the databases you intend to use.
