How to Check if a Relationship `exists()` in Eloquent

Table Of Contents

• The Performance Problem
• Laravel Relationship Existence Methods
• Advanced Relationship Existence Patterns

The Performance Problem

Loading models just to check if relationships exist wastes memory and database resources. Laravel's relationship existence methods solve this elegantly:

// SLOW - Loads all posts to check comments
$postsWithComments = Post::with('comments')->get()->filter(function ($post) {
    return $post->comments->count() > 0;
});

// FAST - Database-level existence check
$postsWithComments = Post::has('comments')->get();

// Even more specific - posts with approved comments only
$postsWithApprovedComments = Post::whereHas('comments', function ($query) {
    $query->where('approved', true);
})->get();

// Check if specific post has comments
$post = Post::find(1);
$hasComments = $post->comments()->exists(); // Returns boolean

// Count vs exists for performance
$commentCount = $post->comments()->count();     // Returns integer
$hasAnyComments = $post->comments()->exists();  // Returns boolean (faster)

Laravel Relationship Existence Methods

Each method serves different purposes for checking relationship existence:

// has() - Check if relationship exists
$usersWithPosts = User::has('posts')->get();
$usersWithMultiplePosts = User::has('posts', '>=', 5)->get();

// whereHas() - Check existence with conditions
$usersWithRecentPosts = User::whereHas('posts', function ($query) {
    $query->where('created_at', '>', now()->subDays(30));
})->get();

// doesntHave() - Opposite of has()
$usersWithoutPosts = User::doesntHave('posts')->get();

// whereDoesntHave() - Opposite of whereHas()
$usersWithoutRecentPosts = User::whereDoesntHave('posts', function ($query) {
    $query->where('created_at', '>', now()->subDays(30));
})->get();

// exists() on relationship instance
$user = User::find(1);
if ($user->posts()->exists()) {
    // User has at least one post
}

// Multiple relationship checks
$activeUsersWithRecentPosts = User::where('active', true)
    ->has('posts')
    ->whereHas('posts', function ($query) {
        $query->where('published_at', '>', now()->subWeek());
    })->get();

Advanced Relationship Existence Patterns

Complex scenarios require combining multiple existence checks:

// Nested relationships - users with posts that have comments
$usersWithCommentedPosts = User::whereHas('posts.comments')->get();

// Multiple relationship conditions
$popularAuthors = User::whereHas('posts', function ($query) {
    $query->where('views', '>', 1000);
})->whereHas('comments', function ($query) {
    $query->where('created_at', '>', now()->subMonth());
})->get();

// Conditional existence checks
$query = User::query();

if (request('has_posts')) {
    $query->has('posts');
}

if (request('has_recent_activity')) {
    $query->where(function ($q) {
        $q->has('posts')->orHas('comments');
    });
}

$users = $query->get();

// Performance tip: Use exists() for boolean checks
public function hasUnreadNotifications()
{
    return $this->notifications()->where('read_at', null)->exists();
}

// Instead of count() > 0
public function hasUnreadNotificationsSlow()
{
    return $this->notifications()->where('read_at', null)->count() > 0;
}

// Raw existence check for complex conditions
$hasComplexRelation = DB::table('users')
    ->whereExists(function ($query) {
        $query->select(DB::raw(1))
              ->from('posts')
              ->whereColumn('posts.user_id', 'users.id')
              ->where('posts.status', 'published')
              ->where('posts.views', '>', 1000);
    })->exists();

The exists() method is more efficient than count() > 0 because it stops at the first matching record. Use has() and whereHas() for filtering collections, and exists() on relationship instances for boolean checks.

Related: Laravel Collections: Beyond Basic Array Operations | Advanced Eloquent Techniques and Optimizations in Laravel | Building Multi-tenant Applications with Laravel: A Comprehensive Guide