Custom Eloquent BelongsTo

PROGRESS UPDATE:

I can create views and use this views for the models which work great for SELECT and UPDATE queries, but fail for INSERT queries (see code at bottom).

At this point, I feel like my options are try to modify the Eloquent models to target the real, non-view table for INSERTs, or maybe there's a pre-INSERT hook where I can create a record behind the scenes and silently convert any School::create() or $school->save() that's an INSERT into an INSERT on the real table, followed by an UPDATE on the view. Hmmm, maybe I can override function save() and static function create() on these models to use the proper table...

Ideally there's a more seamless way in MariaDB to add a 'synthetic' read-only column like this such that Laravel treats it like a proper table more universally.

CREATE VIEW schools_with_de_facto_foo AS
SELECT 
    `schools`.*,
    IF(`schools`.foo_id, `schools`.foo_id, `districts`.foo_id) as de_facto_foo_id
FROM `schools` 
LEFT JOIN `districts` on `districts`.id = `schools`.district_id;

CREATE VIEW studios_with_de_facto_foo AS
SELECT 
    `studios`.*,
    IF(`studios`.foo_id, `studios`.foo_id, 
        IF(`schools`.foo_id, `schools`.foo_id, d.foo_id)
    )
    as de_facto_foo_id
FROM `studios`
LEFT JOIN `schools` on `schools`.id = `studios`.school_id
LEFT JOIN `districts` d on d.id = `schools`.district_id;

MariaDB documentation says:

A view cannot be used for inserting if it fails any of the criteria for updating, and must also meet the following conditions:

• the view contains all base table columns that don't have default values
• no base table columns are present in view select list more than once
• the view columns are all simple columns, and not derived in any way. The following are examples of derived columns
  • column_name + 25
  • LOWER(column_name)
  • (subquery)
  • 9.5
  • column1 / column2

Getting closer.

I added the views and then the following to the models:

School.php

<?php

namespace App\Models;

use App\Models\Foo;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\BelongsTo;

class School extends Model
{

    /**
     * The table associated with the model.
     *
     * @var string
     */
    protected $table = 'schools_with_de_facto_foo';

    #[\Override]
    public function delete()
    {
        $this->table = 'schools';
        return parent::delete();
    }

    #[\Override]
    public function save(array $options = [])
    {
        $this->table = 'schools';
        return parent::save($options);
    }

    /**
     * The Foo associated with this school, or parent District.
     */
    public function deFactoFoo: BelongsTo
    {
        return $this->belongsTo(Foo::class, 'de_facto_foo_id');
    }

}

I did have to wrestle a little bit with some foreign key stuff that's particular to my implementation, but that's pretty much settled. The only thing now is that the fresh() and refresh() functions will not hydrate deFactoFoo. It's not clear to me why.