Django object-relational mapping (ORM) comes with special abstraction constructs that can be used to build complex database queries. They are called query expressions, and they allow you to filter data, order it, annotate new columns, and aggregate relations. In this recipe, you will see how that can be used in practice. We will create an app that shows viral videos and counts how many times each video has been seen by anonymous (versus logged-in) users.
Using database query expressions
by Aidas Bendoraitis, Jake Kronika
Django 2 Web Development Cookbook - Third Edition
- Title Page
- Copyright and Credits
- Dedication
- Packt.com
- Contributors
- Preface
- Getting Started with Django 2.1
- Introduction
- Working with a virtual environment
- Creating a virtual environment project file structure
- Working with Docker
- Creating a Docker project file structure
- Handling project dependencies with pip
- Including external dependencies in your project
- Configuring settings for development, testing, staging, and production environments
- Defining relative paths in the settings
- Creating and including local settings
- Setting up STATIC_URL dynamically for Subversion users
- Setting up STATIC_URL dynamically for Git users
- Setting UTF-8 as the default encoding for MySQL configuration
- Setting the Subversion ignore property
- Creating the Git ignore file
- Deleting Python-compiled files
- Respecting the import order in Python files
- Creating app configuration
- Defining overwritable app settings
- Database Structure and Modeling
- Introduction
- Using model mixins
- Creating a model mixin with URL-related methods
- Creating a model mixin to handle creation and modification dates
- Creating a model mixin to take care of meta tags
- Creating a model mixin to handle generic relations
- Handling multilingual fields
- Enabling schema microdata enhancements
- Using migrations
- Switching from South migrations to Django migrations
- Changing a foreign key to the many-to-many field
- Forms and Views
- Introduction
- Passing HttpRequest to a form
- Utilizing the save method of the form
- Uploading images
- Creating a form layout with custom templates
- Creating a form layout with django-crispy-forms
- Filtering object lists
- Managing paginated lists
- Composing class-based views
- Generating PDF documents
- Implementing a multilingual search with Haystack and Whoosh
- Templates and JavaScript
- Customizing Template Filters and Tags
- Introduction
- Following conventions for your own template filters and tags
- Creating a template filter to show how much time has passed since a post was published
- Creating a template filter to extract the first media object
- Creating a template filter to humanize URLs
- Creating a template tag to include a template if it exists
- Creating a template tag to load a QuerySet in a template
- Creating a template tag to parse content as a template
- Creating a template tag to modify request query parameters
- Model Administration
- Security and Performance
- Introduction
- Making forms secure from Cross Site Request Forgery (CSRF)
- Implementing password validation
- Downloading authorized files
- Adding a dynamic watermark to images
- Authenticating with Auth0
- Caching the method return value
- Using Memcached to cache Django views
- Using Redis to cache Django views
- Django CMS
- Hierarchical Structures
- Introduction
- Creating hierarchical categories with django-mptt
- Creating a category administration interface with django-mptt-admin
- Rendering categories in a template with django-mptt
- Using a single selection field to choose a category in forms with django-mptt
- Using a checkbox list to choose multiple categories in forms with django-mptt
- Creating hierarchical categories with django-treebeard
- Creating a basic category administration interface with django-treebeard
- Importing and Exporting Data
- Bells and Whistles
- Testing and Deployment
- Other Books You May Enjoy
Using database query expressions
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