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ORM Django

Let's create a small project for practicing the handling data using the ORM offered by Django.

  1. Create a virtual enviroment and active it:

    path-to-the-project>py -m venv env
    (env) path-to-the-project\env\Scripts>

  2. Install Django:

    (env) path-to-the-project>pip install django

  3. Create a project:

    (env) path-to-the-project>django-admin startproject learning_django

  4. Run the server:

    (env) path-to-the-project\learning_django>py manage.py runserver

    At the moment we can get this:

  5. Create an app called ORM and register it in learning_django/settings.py:

    path-to-the-project\learning_django>py manage.py startapp orm

    # Application definition
        'orm', # Register the app orm

  6. Register the Templates and Static directories:

    We are going to use some HTML templates, then let's register the "templates" directory and the "static" directory at learning_django/settings.py and create "templates" directory at project's root and "orm/templates" directory.

    # Templates
            'BACKEND': 'django.template.backends.django.DjangoTemplates',
            'DIRS': ['templates'],
            'APP_DIRS': True,
            'OPTIONS': {
                'context_processors': [

    Static directory:

    # Static directory
    STATIC_URL = 'static/'
    STATICFILES_DIRS = ['static', ]

  7. Set the connection to Database:

    In this case, I am going to use a MariaDB database, this is set at learning_django/settings.py:

        'default': {
            'ENGINE': 'django.db.backends.mysql',
            'NAME': 'django_orm',
            'USER': 'root',
            'PASSWORD': '',
            'HOST': 'localhost',
            'PORT': '3306',

  8. Create the database:

    Create a database called "django_orm", the tables will be created by migrations. In this example we are using MySQL or MariaDB.

  9. Install the driver for connecting to MySQL Databases:

    (env) path-to-the-project\learning_django>pip install mysqlclient

  10. Create the following views in orm/views.py:

    from django.shortcuts import render
    from django.http import HttpResponse
    # Create your views here.
    def sql_where(request):
        return HttpResponse('where')
    def sql_insert(request):
        return HttpResponse('insert')
    def sql_update(request):
        return HttpResponse('update')
    def sql_delete(request):
        return HttpResponse('delete')
    def sql_join(request):
        return HttpResponse('join')

  11. Create the "orm/urls.py" file and register the urls for the views:

    from django.urls import path
    from . import views
    app_name = 'orm' # namespace for app's urls
    urlpatterns = [
        # path(url,function,name for this url)
        # ex: /orm/insert
        path('insert', views.sql_insert, name='insert'),
        path('where', views.sql_where, name='where'),
        path('update', views.sql_update, name='update'),
        path('delete', views.sql_delete, name='delete'),
        path('join', views.sql_join, name='join'),

  12. Include the ORM's urls in the project's urls:

    Set the file learning_django/urls.py:

    from django.contrib import admin
    from django.urls import path, include
    urlpatterns = [
        path('orm/', include('orm.urls')),
        path('admin/', admin.site.urls),

    At this moment we can run the server to get this:

    (env) path-to-the-project\learning_django>py manage.py runserver

    and the same for where, delete and join.

  13. Create the models:

    At orm/models set:

    from django.db import models
    # Create your models here.
    class Country(models.Model):
        id = models.AutoField(primary_key=True)
        country = models.CharField(max_length=255,unique=True)
    class Department(models.Model):
        department = models.CharField(max_length=255,null=False,unique=True)
    class Product(models.Model):
        product = models.CharField(max_length=255)
        origin = models.ForeignKey(Country,null=True,on_delete=models.SET_NULL)
        price = models.FloatField(null=False,blank=False)

  14. Make migrations:

    (env) path-to-the-project/learn_django>py manage.py makemigrations orm

    The console should answer:

    Migrations for 'orm':
        - Create model Country
        - Create model Department
        - Create model Product

    For whatching the SQL changes taht will be executed:

    (env) path-to-the-project/learn_django>py manage.py sqlmigrate orm 0001

    The console should answer:

    -- Create model Country
    CREATE TABLE `orm_country` (`id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY, `country` varchar(255) NOT NULL UNIQUE);
    -- Create model Department
    CREATE TABLE `orm_department` (`id` bigint AUTO_INCREMENT NOT NULL PRIMARY KEY, `department` varchar(255) NOT NULL UNIQUE);
    -- Create model Product
    CREATE TABLE `orm_product` (`id` bigint AUTO_INCREMENT NOT NULL PRIMARY KEY, `product` varchar(255) NOT NULL, `price` double precision NOT NULL, `origin_id` integer NULL);
    CREATE TABLE `orm_product_department` (`id` bigint AUTO_INCREMENT NOT NULL PRIMARY KEY, `product_id` bigint NOT NULL, `department_id` bigint NOT NULL);
    ALTER TABLE `orm_product` ADD CONSTRAINT `orm_product_origin_id_37ac325a_fk_orm_country_id` FOREIGN KEY (`origin_id`) REFERENCES `orm_country` (`id`);
    ALTER TABLE `orm_product_department` ADD CONSTRAINT `orm_product_department_product_id_department_id_fa4e7392_uniq` UNIQUE (`product_id`, `department_id`);
    ALTER TABLE `orm_product_department` ADD CONSTRAINT `orm_product_department_product_id_a654837b_fk_orm_product_id` FOREIGN KEY (`product_id`) REFERENCES `orm_product` (`id`);       
    ALTER TABLE `orm_product_department` ADD CONSTRAINT `orm_product_departme_department_id_eb5711f7_fk_orm_depar` FOREIGN KEY (`department_id`) REFERENCES `orm_department` (`id`);  

    Finally, excecute the migration:

    (env) path-to-the-project/learn_django>py manage.py migrate

    If we check the database we should find some tables were created. Some of them are from models built-in in Django and there are some tables which name begin with "orm_", those last were created for our ORM model.

Thanks for reading :)
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