Contenuti del Corso

Django ORM Ninja: Advanced Techniques for Developers

1. Introduction to Django ORM

Introduction to the Course Introduction to the ORM Start a New Project Initialize a New Project

2. Models, datatypes, and fields

Defining The First Model Field Data Types Define Other Models Migrations Admin Interface

3. Queries

Create Query Retrieve Query Lazy Queries Ordering and Slicing Updating Deleting

4. Relations

Many-to-One ForeignKey Arguments One-to-One Many-to-Many

5. Complex Queries

Field Lookups Q and F Objects Aggregations Annotations Minimazing Database Hints

6. Advanced

Class Meta Constrains Transactions Basics User Model

Aggregations

Do you remember that aggregations in SQL are used to compute a single result from a set of input values. Let's remind some common aggregation functions: COUNT, SUM, AVG, MAX, MIN.

At the same time, Aggregation in Django ORM is a powerful tool to perform calculations over query sets, enabling you to summarize or analyze data efficiently. It allows for operations like counting, averaging, summing, etc., across a set of records.

Basic Aggregation Examples

This query counts how many books each author has written.

from django.db.models import Count
author_book_count = Author.objects.annotate(num_books=Count("books"))

Complex Aggregation

Finds the latest publication date for each author.

from django.db.models import Max
latest_book_per_author = Author.objects.annotate(latest_publication=Max("books__publication_date"))

Aggregation with Filters

Aggregates the total pages of all books in the "Fantasy" genre.

total_pages_fantasy = Book.objects.filter(genre__name="fantasy").aggregate(Sum("pages"))

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Sezione 5. Capitolo 3

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Contenuti del Corso

Django ORM Ninja: Advanced Techniques for Developers

1. Introduction to Django ORM

Introduction to the Course Introduction to the ORM Start a New Project Initialize a New Project

2. Models, datatypes, and fields

Defining The First Model Field Data Types Define Other Models Migrations Admin Interface

3. Queries

Create Query Retrieve Query Lazy Queries Ordering and Slicing Updating Deleting

4. Relations

Many-to-One ForeignKey Arguments One-to-One Many-to-Many

5. Complex Queries

Field Lookups Q and F Objects Aggregations Annotations Minimazing Database Hints

6. Advanced

Class Meta Constrains Transactions Basics User Model

Aggregations

Basic Aggregation Examples

This query counts how many books each author has written.

from django.db.models import Count
author_book_count = Author.objects.annotate(num_books=Count("books"))

Complex Aggregation

Finds the latest publication date for each author.

from django.db.models import Max
latest_book_per_author = Author.objects.annotate(latest_publication=Max("books__publication_date"))

Aggregation with Filters

Aggregates the total pages of all books in the "Fantasy" genre.

total_pages_fantasy = Book.objects.filter(genre__name="fantasy").aggregate(Sum("pages"))

Tutto è chiaro?

Grazie per i tuoi commenti!

Sezione 5. Capitolo 3

Django ORM Ninja: Advanced Techniques for Developers

Aggregations

Basic Aggregation Examples

Complex Aggregation

Aggregation with Filters

1. What is the primary use of aggregation functions in SQL?

2. What does the following Django ORM query do? Author.objects.annotate(latest_publication=Max('books__publication_date'))

3. Which Django ORM query is used to aggregate the total pages of all books in the 'Fantasy' genre?

Django ORM Ninja: Advanced Techniques for Developers

Aggregations

Basic Aggregation Examples

Complex Aggregation

Aggregation with Filters

1. What is the primary use of aggregation functions in SQL?

2. What does the following Django ORM query do? Author.objects.annotate(latest_publication=Max('books__publication_date'))

3. Which Django ORM query is used to aggregate the total pages of all books in the 'Fantasy' genre?