Laravel Deep Relation Data Fetching

has-many-deep.md

Deep Relations in Laravel: Handling Course-Episode Relationships

In Laravel, you often deal with relationships that span multiple tables. Here's a quick guide to counting related data through deep relations:

Option 1: Using hasManyThrough

When you store a direct reference like course_id in the episodes table, you can establish a deep relation using hasManyThrough. This is perfect for counting through intermediate relationships.

// file: Topic.php
public function episodes()
{
    return $this->hasManyThrough(Episode::class, Course::class);
}

// file: 2024_05_01_095831_create_episodes_table
Schema::create('episodes', function (Blueprint $table) {
    $table->id();
    $table->foreignId('course_id')->constrained()->onDelete('cascade');
    $table->foreignId('section_id')->constrained()->onDelete('cascade');
    // other fields...
});

Option 2: Using hasManyDeep

If you prefer not to add course_id to the episodes table, the staudenmeir/eloquent-has-many-deep package allows you to traverse deep relationships without direct references.

// Required package: composer require staudenmeir/eloquent-has-many-deep

// file: Topic.php
use HasRelationships; // Import this for 'hasManyDeep'

public function episodes()
{
    return $this->hasManyDeep(Episode::class, [Course::class, Section::class]);
}

With these setups, you can fetch data along with relationship counts in one go:

// Retrieve topics with counts of associated courses and episodes
Topic::withCount(['courses', 'episodes'])->get();

This fetches all topics and adds the count of related courses and episodes, enabling you to manage deep relationships efficiently.