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5. Eloquent Custom Relations: Building a HasManyThrough Alternative with Query Builder

 Eloquent Custom Relations: Building a HasManyThrough Alternative with Query Builder
====================================================================================

 Standard Eloquent relations don't cover every schema. Learn how to build a fully functional custom relation class that integrates with eager loading, lazy loading, and query constraints.

 ![](https://cdn.msaied.com/01M22N44A70A5MC2S599JP0MPH.webp) [Mohamed Said](https://www.msaied.com/public#person) Published 2 Jul 2026 · Updated 2 Jul 2026 · 1 min read

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 ![Eloquent Custom Relations: Building a HasManyThrough Alternative with Query Builder](https://cdn.msaied.com/341/e460f72ab8bb3d94f0646b12a73167cc.png) 

  On this page +1. [Why Standard Relations Fall Short](#why-standard-relations-fall-short)
2. [Anatomy of an Eloquent Relation](#anatomy-of-an-eloquent-relation)
3. [A Concrete Example: HasManyInPeriod](#a-concrete-example-codehasmanyinperiodcode)
4. [Wiring It Into the Model](#wiring-it-into-the-model)
5. [Handling withCount and Subquery Selects](#handling-codewithcountcode-and-subquery-selects)
6. [Key Takeaways](#key-takeaways)

 Why Standard Relations Fall Short
---------------------------------

Eloquent ships with eight relation types. They cover the common cases well, but real-world schemas often involve multi-column joins, filtered pivot conditions, or cross-schema links that don't map cleanly onto `HasManyThrough` or `BelongsToMany`. The usual workaround is a raw `join` inside a scope, which breaks eager loading and pollutes your model with query logic.

The cleaner path is a custom `Relation` subclass. It's less magic than it looks.

Anatomy of an Eloquent Relation
-------------------------------

Every relation extends `Illuminate\Database\Eloquent\Relations\Relation`. The contract requires three methods:

- `addConstraints()` — applied when loading a single model (lazy load).
- `addEagerConstraints(array $models)` — applied when loading a collection (eager load).
- `initRelation(array $models, $relation)` — seeds each model with a default value before results arrive.
- `match(array $models, Collection $results, $relation)` — maps results back onto their parent models.
- `getResults()` — executes the query and returns the final value.

A Concrete Example: `HasManyInPeriod`
-------------------------------------

Imagine `User` has many `Booking` records, but you always want bookings filtered to an active contract period stored on a `contracts` table. The join condition is non-trivial.

```php