Django Framework

3.

Models: The Data Layer

3.1.

Defining Models

3.1.1.

The `models.Model` Class

3.1.1.1.

Creating a Model Class

3.1.1.2.

Model Class Naming Conventions

3.1.1.3.

Model Docstrings and Meta Information

3.2.

3.2.1.

Common Field Types

3.2.1.1.

3.2.1.2.

3.2.1.3.

3.2.1.4.

3.2.1.5.

3.2.1.6.

3.2.1.7.

`DateTimeField`

3.2.1.8.

3.2.1.9.

3.2.1.10.

3.2.1.11.

3.2.1.12.

3.2.1.13.

3.2.1.14.

`PositiveIntegerField`

3.2.1.15.

`BigIntegerField`

3.2.1.16.

3.2.1.17.

`DurationField`

3.2.1.18.

3.2.1.19.

3.2.2.

3.2.2.1.

3.2.2.2.

3.2.2.3.

3.2.2.4.

3.2.2.5.

3.2.2.6.

3.2.2.7.

3.2.2.8.

3.2.2.9.

3.2.2.10.

3.2.2.11.

3.2.2.12.

`decimal_places`

3.2.2.13.

3.2.2.14.

3.2.2.15.

3.3.

3.3.1.

Foreign Keys (`ForeignKey`)

3.3.1.1.

Defining Foreign Keys

3.3.1.2.

Related Name and Related Query Name

3.3.1.3.

On Delete Behaviors

3.3.1.3.1.

3.3.1.3.2.

3.3.1.3.3.

3.3.1.3.4.

3.3.1.3.5.

3.3.1.3.6.

3.3.2.

Many-to-Many Relationships (`ManyToManyField`)

3.3.2.1.

Defining Many-to-Many Fields

3.3.2.2.

3.3.2.3.

Symmetrical Relationships

3.3.2.4.

Related Name in Many-to-Many

3.3.3.

One-to-One Relationships (`OneToOneField`)

3.3.3.1.

Use Cases for One-to-One

3.3.3.2.

Defining One-to-One Fields

3.3.3.3.

Parent Link Fields

3.4.

3.4.1.

Creating Migrations with `makemigrations`

3.4.1.1.

Automatic Migration Detection

3.4.1.2.

Naming Migrations

3.4.1.3.

Empty Migrations

3.4.2.

Applying Migrations with `migrate`

3.4.2.1.

Forward Migrations

3.4.2.2.

Fake Migrations

3.4.3.

Understanding Migration Files

3.4.3.1.

Migration File Structure

3.4.3.2.

Dependencies and Operations

3.4.3.3.

Migration Operations

3.4.3.3.1.

3.4.3.3.2.

3.4.3.3.3.

3.4.3.3.4.

3.4.3.3.5.

3.4.3.3.6.

3.4.3.3.7.

3.4.3.3.8.

3.4.4.

Inspecting SQL with `sqlmigrate`

3.4.5.

Rolling Back Migrations

3.4.5.1.

Unapplying Migrations

3.4.5.2.

Migration History

3.4.6.

Managing Migration Conflicts

3.4.6.1.

Merge Migrations

3.4.6.2.

Squashing Migrations

3.4.7.

Data Migrations

3.4.7.1.

Creating Data Migrations

3.4.7.2.

Writing Migration Functions

3.5.

The Django ORM (Object-Relational Mapper)

3.5.1.

3.5.1.1.

Definition and Characteristics

3.5.1.2.

Lazy Evaluation

3.5.1.3.

QuerySet Caching

3.5.1.4.

Evaluating QuerySets

3.5.2.

Creating Objects

3.5.2.1.

Using `create()`

3.5.2.2.

3.5.2.3.

Using `get_or_create()`

3.5.2.4.

Using `update_or_create()`

3.5.2.5.

Bulk Creation with `bulk_create()`

3.5.3.

Retrieving Objects

3.5.3.1.

3.5.3.2.

3.5.3.3.

Using `filter()`

3.5.3.4.

Using `exclude()`

3.5.3.5.

Using `first()` and `last()`

3.5.3.6.

Using `order_by()`

3.5.3.7.

Using `distinct()`

3.5.3.8.

Using `values()` and `values_list()`

3.5.3.9.

Using `only()` and `defer()`

3.5.3.10.

Using `select_related()`

3.5.3.11.

Using `prefetch_related()`

3.5.4.

Updating Objects

3.5.4.1.

Modifying Fields and Saving

3.5.4.2.

Using `update()`

3.5.4.3.

Bulk Updates with `bulk_update()`

3.5.5.

Deleting Objects

3.5.5.1.

Using `delete()`

3.5.5.2.

Cascading Deletes

3.5.5.3.

3.6.

Advanced Querying

3.6.1.

3.6.1.1.

3.6.1.2.

3.6.1.3.

3.6.1.4.

3.6.1.5.

3.6.1.6.

3.6.1.7.

3.6.1.8.

3.6.1.9.

3.6.1.10.

3.6.1.11.

3.6.1.12.

3.6.1.13.

3.6.1.14.

3.6.1.15.

3.6.2.

Chaining Filters

3.6.3.

Q Objects for Complex Lookups

3.6.3.1.

Combining Queries with Q

3.6.3.2.

Negating Queries

3.6.3.3.

OR and AND Operations

3.6.4.

F Expressions for Field References

3.6.4.1.

Field-to-Field Comparisons

3.6.4.2.

Avoiding Race Conditions

3.6.4.3.

Mathematical Operations

3.6.5.

3.6.5.1.

3.6.5.2.

3.6.5.3.

3.6.5.4.

Using `Min` and `Max`

3.6.5.5.

Using `StdDev` and `Variance`

3.6.6.

3.6.6.1.

Adding Calculated Fields to QuerySets

3.6.6.2.

Conditional Annotations with `Case` and `When`

3.6.7.

3.6.7.1.

Using `Subquery`

3.6.7.2.

Using `OuterRef`

3.6.7.3.

3.6.8.

Raw SQL Queries

3.6.8.1.

3.6.8.2.

Using `extra()`

3.6.8.3.

Direct Database Connections

3.7.

3.7.1.

Default Manager

3.7.2.

Overriding the Default Manager

3.7.3.

Creating Custom Manager Methods

3.7.4.

Using Managers in Queries

3.7.5.

Manager Inheritance

3.8.

3.8.1.

Instance Methods

3.8.2.

3.8.3.

3.8.4.

The `str()` Method

3.8.5.

The `get_absolute_url()` Method

3.8.6.

Custom Save and Delete Methods

3.9.

Model Meta Options

3.9.1.

3.9.2.

3.9.3.

`verbose_name_plural`

3.9.4.

3.9.5.

`unique_together`

3.9.6.

`index_together`

3.9.7.

3.9.8.

3.9.9.

3.9.10.

3.9.11.

`default_permissions`

3.9.12.

`get_latest_by`

3.9.13.

3.9.14.

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4. Views: The Logic Layer