Django Many-to-One Relationships

Django Tutorial

About Lesson

In this Django tutorial we want to learn about Django Many-To-One Relationships, there are different models relationships in django, we have Many-to-One Relationships, One-to-One Relationships and Many-to-Many Relationships. basically in this lesson we want to learn about Django Many-to-One Relationships, so a many to one relationship implies that one model record can have many other model records associated with itself. To define this relationship in Django models you use the ForeignKey data type on the model that has the many records .

In this example we want to create a new Choice model and we want to create a many-to-one Relationship between the Question and Choice model, so this is our model basically we have three fields for this model and the first field is the relationship field.

class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

class Choice(models.Model):

question = models.ForeignKey(Question, on_delete=models.CASCADE)

choice_text = models.CharField(max_length=200)

votes = models.IntegerField(default=0)

So this is our complete models.py file.

from django.db import models

# Create your models here.

class Question(models.Model):
    text = models.CharField(max_length=100)
    pub_date = models.DateTimeField('date published')


    def __str__(self):
        return self.text




class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

    def __str__(self):
        return self.text

from django.db import models

# Create your models here.

class Question(models.Model):

text = models.CharField(max_length=100)

pub_date = models.DateTimeField('date published')

def __str__(self):

return self.text

class Choice(models.Model):

question = models.ForeignKey(Question, on_delete=models.CASCADE)

choice_text = models.CharField(max_length=200)

votes = models.IntegerField(default=0)

def __str__(self):

return self.text

After creating of a new model in django, you need to do migration and after that migrate your project.

python manage.py makemigrations

1	python manage.py makemigrations

python manage.py migrate

1	python manage.py migrate

So after doing this you will see that we have added a table in to our database.

Now let’s register our this model in our admin.py file, so open your admin.py file and add this.

admin.site.register(Choice)

1	admin.site.register(Choice)

This is our complete admin.py file.

from django.contrib import admin
from .models import Question, Choice

# Register your models here.

#first way
#admin.site.register(Question)


#second way
@admin.register(Question)
class QuestionModel(admin.ModelAdmin):
    list_filter = ('text', 'pub_date')
    list_display = ('text', 'pub_date')
    date_hierarchy = ('pub_date')
    ordering = ('pub_date', 'text')


admin.site.register(Choice)

from django.contrib import admin

from .models import Question, Choice

# Register your models here.

#first way

#admin.site.register(Question)

#second way

@admin.register(Question)

class QuestionModel(admin.ModelAdmin):

list_filter = ('text', 'pub_date')

list_display = ('text', 'pub_date')

date_hierarchy = ('pub_date')

ordering = ('pub_date', 'text')

admin.site.register(Choice)

And this is our django admin panel.

Rest of the file for this tutorial.

mysite/templates/base.html

<!DOCTYPE html>
{% load static %}
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>{% block title %}{% endblock %}</title>

    <!-- CSS -->
<link rel="stylesheet"
      href="https://cdn.jsdelivr.net/npm/bootstrap@4.5.3/dist/css/bootstrap.min.css" >

    <link rel="stylesheet" href="{% static 'css/style.css' %}">

</head>
<body>
{% include 'navbar.html' %}

{% block body %}

{% endblock %}

<!-- jQuery and JS bundle w/ Popper.js -->
<script src="https://code.jquery.com/jquery-3.5.1.slim.min.js" >

</script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap@4.5.3/dist/js/
bootstrap.bundle.min.js" ></script>


</body>
</html>

<!DOCTYPE html>

{% load static %}

<head>

<title>{% block title %}{% endblock %}</title>

href="https://cdn.jsdelivr.net/npm/bootstrap@4.5.3/dist/css/bootstrap.min.css" >

</head>

<body>

{% include 'navbar.html' %}

{% block body %}

{% endblock %}

</script>

bootstrap.bundle.min.js" ></script>

</body>

</html>

mysite/templates/navbar.html

<nav class="navbar navbar-expand-lg navbar navbar-dark bg-dark">
  <a class="navbar-brand" href="{% url 'index' %}">GeeksCoders</a>
  <button class="navbar-toggler" type="button"
          data-toggle="collapse" data-target="#navbarNavAltMarkup"
          aria-controls="navbarNavAltMarkup" aria-expanded="false"
          aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>
  <div class="collapse navbar-collapse" id="navbarNavAltMarkup">
    <div class="navbar-nav">
      <a class="nav-link active" href="{% url 'index' %}">Home
          <span class="sr-only">(current)</span></a>
      <a class="nav-link" href="{% url 'polls_list' %}">Polls</a>

    </div>
  </div>
</nav>

<a class="navbar-brand" href="{% url 'index' %}">GeeksCoders</a>

<button class="navbar-toggler" type="button"

data-toggle="collapse" data-target="#navbarNavAltMarkup"

aria-controls="navbarNavAltMarkup" aria-expanded="false"

aria-label="Toggle navigation">

</button>

<a class="nav-link active" href="{% url 'index' %}">Home

<span class="sr-only">(current)</span></a>

<a class="nav-link" href="{% url 'polls_list' %}">Polls</a>

</div>

</nav>

mysite/templates/index.html

{% extends 'base.html' %}


{% block title %} Home {% endblock %}


{% block body %}

<div class="container">

    <h1>Welcome to GeeksCoders.com</h1>
<p>Tutorial Number 13 - Many to One Relationship</p>

</div>


{% endblock %}

{% extends 'base.html' %}

{% block title %} Home {% endblock %}

{% block body %}

<h1>Welcome to GeeksCoders.com</h1>

<p>Tutorial Number 13 - Many to One Relationship</p>

</div>

{% endblock %}

mysite/templates/polls_list.html

{% extends 'base.html' %}


{% block title %} Polls List {% endblock %}


{% block body %}

<div class="container">

    <h1>Polls List Page</h1>

    {% for poll in polls %}
    <ul class="list-group">
        <li class="list-group-item">
            {{poll}}
        </li>
    </ul>
    {% endfor %}
</div>


{% endblock %}

{% extends 'base.html' %}

{% block title %} Polls List {% endblock %}

{% block body %}

<h1>Polls List Page</h1>

{% for poll in polls %}

</li>

</ul>

{% endfor %}

</div>

{% endblock %}

mysite/polls/views.py

from django.shortcuts import render
from .models import Question

# Create your views here.

def Index(request):
    context = {}

    return render(request, 'index.html', context)
    


def Polls(request):

    polls = Question.objects.all()
    context = {'polls':polls}

    return render(request, 'polls_list.html', context)

from django.shortcuts import render

from .models import Question

# Create your views here.

def Index(request):

context = {}

return render(request, 'index.html', context)

def Polls(request):

polls = Question.objects.all()

context = {'polls':polls}

return render(request, 'polls_list.html', context)

mysite/polls/urls.py

from django.urls import path
from .views import Index, Polls
urlpatterns = [
    path('', Index, name = 'index'),
    path('polls/', Polls, name = 'polls_list')
]

from django.urls import path

from .views import Index, Polls

urlpatterns = [

path('', Index, name = 'index'),

path('polls/', Polls, name = 'polls_list')

]

mysite/urls.py

from django.contrib import admin
from django.urls import path, include

urlpatterns = [
    path('admin/', admin.site.urls),
    path('', include('polls.urls'))
]

from django.contrib import admin

from django.urls import path, include

urlpatterns = [

path('admin/', admin.site.urls),

path('', include('polls.urls'))

]