Eager load relationships in laravel with conditions on the relation
Stefan Bogdanescu
Founder & Senior Architect · 2026-06-29
Title: Eager Loading Relationships with Conditions in Laravel for Hierarchical Categories and Products
Body: In Laravel, eager loading is an efficient technique used to load related data from multiple tables simultaneously as part of a single database query. This concept comes in handy when dealing with complex hierarchies like the one described above - categories, children, products, and product types. Eager loading can significantly reduce round trips to the database, improving overall application performance by retrieving all the required information in one go. In this blog post, we will learn how to use eager loading with conditions on the relations to achieve the desired result.
Let's first analyze the relationship between the models involved:
1. Category Model: The 'Category' table has a parent-child relation where each category can have multiple children and vice versa. This is defined in terms of Laravel relationships as `belongsToMany` and `hasMany`.
2. Product Model: A product belongs to a specific category, which is established using the relationship `belongsTo`.
3. Type Model: The 'Type' table corresponds to various product types that can be associated with multiple products through the relation `belongsToMany`.
Now let's focus on the eager loading and conditionally loading products based on their type. Firstly, we need to define our models and relationships as shown below in your previous code snippets. Let's create a helper function to load all the categories with children and products while applying the given condition:
```php
function getParentLineCategoriesWithConditions($SpecificID) {
return ProductCategory::with(['children' => function ($query) {
$query->with('products');
}])->with(['products' => function ($query) use ($SpecificID) {
$query->join('product_type', 'product_type.product_id', '=', 'product.id')
->where('product_type.type_id', '=', $SpecificID);
}])->get();
}
```
This function performs the following tasks:
1. Load categories with their children and products, specifying that we must also eager load their associated products.
2. As a second step, it joins the product table with the 'product_type' table to apply the condition on the type ID - $SpecificID.
To use this function in your code, you can simply call:
```php
$parentLineCategories = getParentLineCategoriesWithConditions($SpecificID);
```
Remember that eager loading is an effective solution for complex database relationships where multiple tables are involved. However, it is crucial to consider the performance implications and choose the most optimized way according to your specific use case. Sometimes, using eager loading with conditions on a particular relation may not be necessary if you can perform the required filtering or pivoting in the application layer instead of at the database level.
In summary, Laravel's powerful ORM allows us to efficiently manage complex relationships and optimize database queries through eager loading techniques. By understanding how these relationships work and using helper functions such as the one we provided above, you can easily load your data with the desired conditions in place, improving performance and reducing round trips to the database.