{"id":329331,"date":"2023-09-28T12:19:37","date_gmt":"2023-09-28T12:19:37","guid":{"rendered":"https:\/\/pythonguides.com\/?p=16383"},"modified":"2023-09-28T12:19:37","modified_gmt":"2023-09-28T12:19:37","slug":"union-operation-on-models-django","status":"publish","type":"post","link":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/2023\/09\/28\/union-operation-on-models-django\/","title":{"rendered":"Union operation on models Django"},"content":{"rendered":"

<\/p>\n

In this Python Django Tutorial<\/a>, I will show you how to perform union operation on models Django<\/strong>.<\/p>\n

You will understand how to perform union operations on querysets that belong to the same model. Also, you will learn how to perform union operations on query sets that belong to different models.<\/p>\n

Union operation on models Django<\/h2>\n

So ‘what is a union operation?’<\/strong>, from a mathematics point of view, suppose you have two sets A = [2,3 5,7]<\/strong> and B = [1,4,5,6]<\/strong>. To perform union between these sets, the symbol U<\/strong> is used like this ‘A’<\/strong> U<\/strong> ‘B’<\/strong>.<\/p>\n

The result of the union is a set [1,2,3,4,5,6,7]<\/strong> that contains all the elements from sets A and B except the duplicate. <\/p>\n

If you see both sets, they have a common element which is 5 but this element is included only one time in the final set after performing the union operation.<\/p>\n

Like that Django supports Set Operations <\/strong>that can be performed on the models. Set Operations are used to get meaningful results from the field stored in the models, under different special conditions.<\/p>\n

Now, you will learn one of the Set Operations, called Union Operation<\/strong>. But where you will use the union operation in Django, well the answer is simple. You will use the union with Django Queryset.<\/p>\n

Suppose you have a model related to the blog and you want to fetch the blog based on different categories. Then to combine these two separate queryset into a single queryset, use the union operation.<\/p>\n

Now you can say union operation in Django allows us to combine multiple queryset into a single queryset.<\/p>\n

The Union Operation<\/strong> can be applied on the same or different models. The fields and data types should match when querysets are from distinct models or even from the same model.<\/p>\n

Also, check: How to Create model in Django<\/a><\/p>\n

Union Operation on the Same Model Using Django<\/h3>\n

I hope that you have a clear understanding of what Union Operation is. Let’s now turn our attention to the practical implementation of union operations.<\/p>\n

Let’s learn how to use the union operation on the same model<\/p>\n

Before starting the demonstration, I’ll show you the model and explain how to create it. For that open the terminal and create a virtual environment named ‘env_union’<\/strong>.<\/p>\n

python -m venv env_union<\/code><\/pre>\n
Then activate the environment using the below code.<\/p>\n
env_union\\Scripts\\activate<\/code><\/pre>\n
Install the latest version of Django.<\/p>\n
pip install django<\/code><\/pre>\n
Create a Django project named ‘django_union’<\/strong> using the below code.<\/p>\n
django-admin startproject django_union<\/code><\/pre>\n
Change the directory to django_union.<\/p>\n
cd django_union<\/code><\/pre>\n
Then create a Django app named ‘union_app’<\/strong> using the below code.<\/p>\n
python manage.py startapp union_app<\/code><\/pre>\n
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\"Union<\/figure>\n<\/div>\n
Now open the Django project in your preferred IDE such as Visual Studio Code.<\/p>\n
Firstly, create the model named ‘Employee’<\/strong> in the model.py<\/strong> file of the Django app ‘union_app’<\/strong> and add the following lines of code.<\/p>\n
from django.db import models\n\nclass Employee(models.Model):\n    first_name = models.CharField(max_length=200)\n    last_name = models.CharField(max_length=200)\n    position = models.CharField(max_length=100)\n    age = models.PositiveIntegerField()\n    \n    def __str__(self):  \n        return \"%s %s %s %s\" % (self.first_name, self.last_name, self.position, self.age)  <\/code><\/pre>\n
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\"Union<\/figure>\n<\/div>\n
In the above code define the model named Employee<\/strong> with field lists first_name<\/strong>, last_name<\/strong>, position of type CharField<\/strong> and age of type PositiveIntegerField<\/strong>.<\/p>\n
Next, register the Employee<\/strong> model by writing the below code in the admin.py<\/strong> file of your Django app ‘union_app’<\/strong>.<\/p>\n
from django.contrib import admin\nfrom .models import Employee\n\nclass AdminEmployee(admin.ModelAdmin):\n    list_display = ['first_name', 'last_name', 'position', 'age']\n\nadmin.site.register(Employee, AdminEmployee)<\/code><\/pre>\n
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\"Union<\/figure>\n<\/div>\n
Include your app in the INSTALLED_APPS<\/strong> list in your setting.py<\/strong> file of the Django project ‘django_union’<\/strong>.<\/p>\n
INSTALLED_APPS = [\n    'django.contrib.admin',\n    'django.contrib.auth',\n    'django.contrib.contenttypes',\n    'django.contrib.sessions',\n    'django.contrib.messages',\n    'django.contrib.staticfiles',\n    'union_app'\n]<\/code><\/pre>\n
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\"Union<\/figure>\n<\/div>\n
Now, run the below commands one by one to make a migration file.<\/p>\n
python manage.py makemigrations\npython manage.py migrate<\/code><\/pre>\n
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\"Union<\/figure>\n<\/div>\n
Open the Python shell by writing the below command in your terminal.<\/p>\n
python manage.py shell<\/code><\/pre>\n
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\"Python<\/figure>\n<\/div>\n
Now use the below command in your Python shell and create some records related to the Employee.<\/p>\n
from union_app.models import Employee\nemp = Employee.objects.create(first_name = \"Maria\", last_name = \"Ted\", position = \"Developer\", age = \"28\")<\/code><\/pre>\n
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\"Python<\/figure>\n<\/div>\n
You can use the above code to create multiple employee records in the database.<\/p>\n
In this example, you will perform Union Operation on the same model. So write the below code in your terminal.<\/p>\n
# Import<\/strong>\n\nfrom union_app.models import Employee\n\n# QuerySet<\/strong>\n\nqueryset1 = Employee.objects.filter(age__gt=28)\nqueryset1\n\nqueryset2 = Employee.objects.filter(first_name=\"Maria\")\nqueryset2\n\n# Union Operation<\/strong>\n\nqueryset1.union(queryset2)<\/code><\/pre>\n
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\"union<\/figure>\n<\/div>\n
In the above code first import the model Employee<\/strong> from the file models.py<\/strong> of your Django app ‘union_app’<\/strong>. <\/p>\n