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1. Open up settings.py on your project, and you can see the default database setting like below
   
   

   Code Block
   # Database # https://docs.djangoproject.com/en/2.1/ref/settings/#databases DATABASES = { 'default': { 'ENGINE': 'django.db.backends.sqlite3', 'NAME': os.path.join(BASE_DIR, 'db.sqlite3'), } }

   If you want to use mysql instead of sqlite3, you can use it by replacing as "django.db.backends.mysql". For oracle, it will be "django.db.backends.oracle". 
   If you are not using SQLite as your database, additional settings such as USER, PASSWORD, and HOST must be added. For more details, see the reference documentation for DATABASES.
   Example)
   
   

   Code Block
   DATABASES = { 'default': { 'ENGINE': 'django.db.backends.postgresql', 'USER': 'mydatabaseuser', 'NAME': 'mydatabase', 'TEST': { 'NAME': 'mytestdatabase', }, }, }

   
   

   Once you set all your requirements, you should run following command.
   
   

   
   

   Code Block
   python manage.py migrate

   
   

   
   

   
   

   
   

2. Creating models for online poll.

   In our simple poll app, we’ll create two models: Question and Choice. A Question has a question and a publication date. A Choice has two fields: the text of the choice and a vote tally. Each Choice is associated with a Question.

   These concepts are represented by simple Python classes. Edit the polls/models.py file so it looks like this:
   
   

   Code Block
   title polls/models.py
   from django.db import models # Create your models here. class Question(models.Model): question_text = models.CharField(max_length=200) pub_date = models.DateTimeField('date published') class Choice(models.Model): question = models.ForeignKey(Question, on_delete=models.CASCADE) choice_text = models.CharField(max_length=200) votes = models.IntegerField(default=0)

   If you see above, it looks like a table schema when we create a table in database. I won't elaborate the detail about above for this time.
   
   

3. Activating models
   Even though we have created an app at the moment, but actually we can't say "polls" are correctly integrated with the project. In django, we should make some additional action to make it happen.
   To include the app in our project, we need to add a reference to its configuration class in the INSTALLED_APPS setting. The PollsConfig class is in the polls/apps.py file,

   Code Block
   language py title polls/apps.py
   from django.apps import AppConfig class PollsConfig(AppConfig): name = 'polls'

   
   so its dotted path is 'polls.apps.PollsConfig'. Edit the <your project folder>/settings.py file and add that dotted path to the INSTALLED_APPS setting. It’ll look like this:

   Code Block
   title <your project folder>/settings.py
   INSTALLED_APPS = [ 'polls.apps.PollsConfig', 'django.contrib.admin', 'django.contrib.auth', 'django.contrib.contenttypes', 'django.contrib.sessions', 'django.contrib.messages', 'django.contrib.staticfiles', ]

   Note that 'polls.apps.PollsConfig' is added on top of 'django.contrib.admin'.

   Now Django knows to include the polls app. Let’s run another command:
   
   

   Code Block
   python manage.py makemigrations polls

   As a result, you should see similar to the following

   Code Block
   Migrations for 'polls': polls/migrations/0001_initial.py - Create model Choice - Create model Question - Add field question to choice

   By running makemigrations, you’re telling Django that you’ve made some changes to your models (in this case, you’ve made new ones) and that you’d like the changes to be stored as a migration.

   Migrations are how Django stores changes to your models (and thus your database schema) - they’re just files on disk. You can read the migration for your new model if you like; it’s the file polls/migrations/0001_initial.py. Don’t worry, you’re not expected to read them every time Django makes one, but they’re designed to be human-editable in case you want to manually tweak how Django changes things.

   There’s a command that will run the migrations for you and manage your database schema automatically - that’s called migrate, and we’ll come to it in a moment - but first, let’s see what SQL that migration would run. The sqlmigrate command takes migration names and returns their SQL:

   Code Block
   python manage.py sqlmigrate polls 0001

   As a result, you should see similar to the following

   Code Block
   language sql
   BEGIN; -- -- Create model Choice -- CREATE TABLE "polls_choice" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "choice_text" varchar(200) NOT NULL, "votes" integer NOT NULL); -- -- Create model Question -- CREATE TABLE "polls_question" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "question_text" varchar(200) NOT NULL, "pub_date" datetime NOT NULL); -- -- Add field question to choice -- ALTER TABLE "polls_choice" RENAME TO "polls_choice__old"; CREATE TABLE "polls_choice" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "choice_text" varchar(200) NOT NULL, "votes" integer NOT NULL, "question_id" integer NOT NULL REFERENCES "polls_question" ("id") DEFERRABLE INITIALLY DEFERRED); INSERT INTO "polls_choice" ("id", "choice_text", "votes", "question_id") SELECT "id", "choice_text", "votes", NULL FROM "polls_choice__old"; DROP TABLE "polls_choice__old"; CREATE INDEX "polls_choice_question_id_c5b4b260" ON "polls_choice" ("question_id"); COMMIT;

   but for now, remember the three-step guide to making model changes:

   1. Change your models (in models.py).

   2. Run python manage.py makemigrations to create migrations for those changes

   3. Run python manage.py migrate to apply those changes to the database.

4.