Laravel withCount() Explained [In-Depth Tutorial]

Laravel is a popular PHP web application framework. It offers a wide range of features and tools to help developers build scalable and robust applications.

The Laravel withCount() method is provided by Laravel's Eloquent ORM to help retrieve a count of related records without having to load them. This can greatly enhance performance when you're only interested in the count rather than the details of the related records.

 

Syntax and usage:

You would typically use withCount() on an Eloquent query builder instance. It's pretty straightforward:

$records = <Model>::withCount('<related_table>')->get();

In this article, we'll explore Laravel's withCount method in detail and demonstrate how it can be used to retrieve related counts of a model's associated data efficiently.

We'll also discuss various use cases and scenarios where withCount can be used effectively to optimize query performance and reduce database overhead.

 

Using withCount() with Different Relationship Types

Using withCount() with One-to-Many relationships

For instance, consider a Post model and a Comment model, where a post can have many comments. If you wish to retrieve all posts with their respective comment count:

$posts = Post::withCount('comments')->get();

foreach ($posts as $post) {
    echo $post->comments_count;
}

 

Using withCount() with Many-to-Many relationships

Imagine a User model and a Role model, where users can have multiple roles and roles can be assigned to multiple users. If you want to get all users along with the number of roles each user has:

$users = User::withCount('roles')->get();

foreach ($users as $user) {
    echo $user->roles_count;
}

 

Using withCount() with Polymorphic Relations

Let's take the example of a Comment model that can be related to both Post and Video models through a polymorphic relation. If you wanted to retrieve all posts along with their respective comment count:

$posts = Post::withCount('comments')->get();

foreach ($posts as $post) {
    echo $post->comments_count;
}

Similarly, to get all videos with their respective comment count:

$videos = Video::withCount('comments')->get();

foreach ($videos as $video) {
    echo $video->comments_count;
}

 

Set up Application Environment

In these steps, we're preparing a foundational environment to demonstrate Laravel's withCount() functionality. Here's a breakdown of what we're doing:

1. Model & Factory Creation: We're creating a Post model to represent articles or entries by users. Alongside this, a factory for the Post model is generated. Factories in Laravel provide a convenient way to create instances of models and store them in the database.
2. Migrations: The migrations will determine the structure of the posts table in our database. Our posts table will have a reference to the user who created the post (the user_id column), ensuring a relationship between users and their posts.
3. Defining Relationships: Within our models, we specify the relationships between User and Post. A user can have many posts (one-to-many relationship), and a post belongs to one user.
4. Factory Definitions: The Post factory is set up to generate sample post data. This includes creating titles, bodies, and assigning each post to a random user.
5. Database Seeding: Using seeders, we populate our database with dummy data. In our example, we're generating 10 users and 100 posts. This simulates a scenario where users have written multiple posts.
6. Migration & Seeding: Finally, the migration command structures our database tables based on our migrations, and the seed command populates these tables with the dummy data we've specified.

Once these steps are completed, our application environment will be ready. We'll have a set of users and their associated posts, allowing us to delve into practical examples showcasing the power and utility of Laravel's withCount() method.

 

Let's start by creating the Post model and factory.

 php artisan make:model Post -mcr
 php artisan make:factory PostFactory --model=Post

Next, open the following files and insert the respective code.

Posts table

Open the database/migrations/<timestamp>_create_posts_table.php file and create a post blue print.

...
    public function up(): void
    {
        Schema::create('posts', function (Blueprint $table) {
            $table->id();
            $table->unsignedBigInteger('user_id');
            $table->string('title');
            $table->text('body');
            $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
            $table->timestamps();
        });
    }
  ...

Post model

Open the app/Models/Post.php file and create the fillable array and user relationship method.

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Post extends Model
{
    use HasFactory;

    protected $fillable = [
        'title',
        'body',
    ];

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

User model

Open the app/Models/User.php file and create the posts relationship method.

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

Post factory

Return the following array from the definition method of the database/factories/PostFactory.php file.

...
        return [
            'title' => fake()->sentence(),
            'body' => fake()->paragraph(),
            'user_id' => rand(1,10),
        ];
...

Database seeder

Open the database/seeders/DatabaseSeeder.php file and create 10 users and 100 posts in the run method.

...
    public function run(): void
    {
        \App\Models\User::factory(10)->create();
        \App\Models\Post::factory(100)->create();
    }
...

Finally, create the database and migrate the changes, while seeding the database.

 php artisan migrate --seed

Now that we have users with posts, we can head straight to the routes/web.php and practice using Laravel withcount.

 

Practical explanation of Laravel withCount()

Example-1: Retrieving Related Model Counts

Open the routes/web.php file and write the following code:

<?php

use App\Models\User;
use Illuminate\Support\Facades\Route;

Route::get('/', function () {
    $users = User::withCount('posts')->get();
    foreach ($users as $user) {
        echo "User {$user->id} has {$user->posts_count} posts.<br>";
    }
});

Using Laravel's withCount method, we retrieve a list of all users and their corresponding number of posts.

First, User::withCount('posts') retrieves all users with a count of their related posts. This creates a new attribute called posts_count on each user model instance, which contains the count of related posts.

Next, get() gets called to execute the query and retrieve the results. This returns a collection of user models, with the posts_count attribute populated for each user.

The foreach loop then iterates over each user in the collection. For each user, the id and posts_count attributes are used to display a message indicating the number of posts each user has. The output of the code is a list of all users and their corresponding post counts.

 

Example-2: Conditional Retrieval of Related Model Counts

Let's get only users with more than 10 posts.

<?php

use App\Models\User;
use Illuminate\Support\Facades\Route;

Route::get('/', function () {
    $users = User::withCount('posts')->having('posts_count', '>', 10)->get();

    foreach ($users as $user) {
        echo "User {$user->id} has {$user->posts_count} posts.<br>";
    }
});

Here's a breakdown of the code:

1. User::withCount('posts') retrieves all users along with a count of their related posts. This creates a new attribute called posts_count on each user model instance, which contains the count of related posts.
2. having('posts_count', '>', 10) filters the results to only include users who have more than 10 posts. This method is called on the query builder instance returned by withCount.
3. get() executes the query and retrieves the results. This returns a collection of user models, with the posts_count attribute populated for each user.
4. The foreach loop then iterates over each user in the collection. For each user, the id and posts_count attributes are used to display a message indicating the number of posts each user has.

The output is a list of users with more than 10 posts and their corresponding post counts.

 

Example-3: Renaming the Count Column

When using withCount(), Laravel by default names the count column as relation_count. But you can customize this if required.

$users = User::withCount(['posts as articles_count'])->get();

foreach ($users as $user) {
    echo $user->name . " has written " . $user->articles_count . " articles.<br>";
}

 

Example-4: Chaining withCount() with other Eloquent Methods

Using withCount() in conjunction with with():

To get users with their posts and also the count of their posts:

$users = User::with('posts')->withCount('posts')->get();

 

Using withCount() with conditional constraints:

If you wanted to count only the posts with a specific condition, say, titles starting with "Hello":

$users = User::withCount(['posts' => function($query) {
    $query->where('title', 'like', 'Hello%');
}])->get();

 

Example-4: Ordering Results Based on Relationship Count

Using the orderBy() method in conjunction with withCount(). To get users ordered by the number of their posts:

$users = User::withCount('posts')->orderBy('posts_count', 'desc')->get();

 

Example-5: Combining withCount() with Lazy Eager Loading

If you've already retrieved a model and want to get the related count afterward, you can use loadCount().

$user = User::first();  // Retrieve the first user as an example
$user->loadCount('posts');  // Load the posts count for this user

echo $user->posts_count;

 

Conclusion

The withCount method in Laravel is a powerful tool that allows you to retrieve the count of related records and the parent records in a single query. This can optimize your database queries and reduce the queries needed to retrieve data.

Using withCount, you can easily retrieve the count of related records for each parent record and even filter the results based on specific conditions using the having method. This makes retrieving data that meets your requirements easy without resorting to multiple queries or complex joins.

Overall, withCount is an excellent addition to Laravel's query builder, and it can save you a lot of time and effort when working with related data. Whether you are building a simple blog or a complex application with many relationships, withCount is a feature you should have in your toolbox.