Elizabeth Mosley

Laravel's Eloquent ORM transforms database interactions into elegant, readable PHP code. Understanding relationships is key to leveraging Eloquent's full power.

One-to-Many: The Most Common Pattern

A user has many posts. A post belongs to one user:

// User model
public function posts() {
    return $this->hasMany(Post::class);
}

// Post model
public function user() {
    return $this->belongsTo(User::class);
}

// Usage
$user = User::find(1);
$posts = $user->posts; // Collection of posts
$author = $post->user; // Single user

Many-to-Many: Tags and Categories

Posts can have many tags, tags can belong to many posts:

// Post model
public function tags() {
    return $this->belongsToMany(Tag::class);
}

// Tag model
public function posts() {
    return $this->belongsToMany(Post::class);
}

// Usage
$post->tags()->attach($tagId);
$post->tags()->detach($tagId);
$post->tags()->sync([1, 2, 3]);

Polymorphic Relations

When multiple models can have the same relationship. Comments on posts, videos, and photos:

// Comment model
public function commentable() {
    return $this->morphTo();
}

// Post model
public function comments() {
    return $this->morphMany(Comment::class, 'commentable');
}

// Usage
$post->comments()->create(['body' => 'Great post!']);

Eager Loading: Avoiding the N+1 Problem

Loading relationships efficiently prevents performance issues:

// Bad: N+1 queries
$posts = Post::all();
foreach($posts as $post) {
    echo $post->user->name; // Query for each post
}

// Good: 2 queries total
$posts = Post::with('user')->get();
foreach($posts as $post) {
    echo $post->user->name; // No additional queries
}

Advanced Queries

Eloquent relationships support query constraints:

$user->posts()
    ->where('published', true)
    ->orderBy('created_at', 'desc')
    ->take(5)
    ->get();

Eloquent relationships make database interactions intuitive while maintaining performance and flexibility.

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