How do I get all children that fall under a parent in eloquent?
Stefan Bogdanescu
Founder & Senior Architect · 2026-06-29
# Navigating Hierarchies in Eloquent: How to Get All Descendant Children Recursively
As developers working with relational data, dealing with hierarchical structures—like organizational trees, file systems, or category structures—is a common challenge. When you establish a recursive relationship in your database, simply using basic Eloquent relationships like `hasMany` often falls short when you need to traverse down multiple levels to retrieve all descendants.
Today, we will dive into how to master this concept in Laravel and Eloquent. We'll explore the best, most performant ways to fetch all products belonging to a parent category, no matter how deeply nested they are within the category tree.
## Setting Up the Recursive Relationship
To handle tree structures effectively in Eloquent, we first need to define our relationships correctly. In your scenario, you have `categories` with a self-referencing relationship (parent/child) and `products` linked to a specific category.
Let's assume the following basic model structure:
```php
// app/Models/Category.php
class Category extends Model
{
public function parent()
{
return $this->belongsTo(Category::class, 'parent_id');
}
public function children()
{
return $this->hasMany(Category::class, 'parent_id');
}
public function products()
{
// This relationship will be used to fetch the final data.
return $this->hasMany(Product::class);
}
}
// app/Models/Product.php
class Product extends Model
{
public function category()
{
return $this->belongsTo(Category::class);
}
}
```
The key is understanding that the direct `products()` relationship only pulls items directly linked to that specific category ID. To achieve recursive loading, we need a strategy to identify *all* relevant category IDs first.
## Strategy 1: Recursive Querying with Subqueries (The Eloquent Way)
For deep hierarchical data, relying solely on nested Eloquent relationships can lead to N+1 query problems or overly complex code. The most efficient way to solve this in Laravel is often by leveraging the power of SQL through Eloquent's query builder to find all relevant parent IDs recursively before fetching the final products.
Since standard Eloquent doesn't have a built-in recursive loading method, we often need to perform a database-level traversal. While complex recursive CTEs (Common Table Expressions) are powerful, a more accessible approach involves finding all relevant category IDs first.
Here is an example demonstrating how you might find all descendant categories and then fetch their associated products:
```php
use App\Models\Category;
use Illuminate\Support\Facades\DB;
class CategoryService
{
public function getProductsFromDescendants(int $categoryId)
{
// 1. Find all category IDs that are descendants of the given category ID, including the parent itself.
$descendantIds = DB::table('categories')
->select('id')
->where('parent_id', $categoryId)
->orWhereExists(function ($query) use ($categoryId) {
$query->select(DB::raw(1))
->from('categories as sub')
->whereColumn('sub.parent_id', 'categories.id')
->whereColumn('sub.id', 'categories.id'); // Recursive check
})
->orWhereExists(function ($query) use ($categoryId) {
$query->select(DB::raw(1))
->from('categories as sub')
->whereColumn('sub.parent_id', 'categories.id')
->whereColumn('sub.id', 'products