Laravel: Order a model by "Has One Of Many" relationship - php

Question

I have a customer model that has many contacts. I defined a relationship to get the most recent contact of the customer using the "Has One Of Many" relationship in Laravel 8:
Models
class Customer extends Model
{
use HasFactory;
public function contacts()
{
return $this->hasMany(Contact::class);
}
public function latestContact()
{
return $this->hasOne(Contact::class)->ofMany('contacted_at', 'max')->withDefault();
}
}
class Contact extends Model
{
use HasFactory;
protected $casts = [
'contacted_at' => 'datetime',
];
public function customer()
{
return $this->belongsTo(Customer::class);
}
}
Migration (contact model)
class CreateContactsTable extends Migration
{
public function up()
{
Schema::create('contacts', function (Blueprint $table) {
$table->id();
$table->timestamps();
$table->softDeletes();
$table->foreignID('customer_id');
$table->string('type');
$table->dateTime('contacted_at');
});
}
}
In my view, I want to show all customers and order them by their latest contact. However, I can't figure out how to do that.
I tried to achieve it via the join method but then I obviously get various entries per customer.
$query = Customer::select('customers.*', 'contacts.contacted_at as contacted_at')
->join('contacts', 'customers.id', '=', 'contacts.customer_id')
->orderby('contacts.contacted_at')
->with('latestContact')
Knowing Laravel there must be a nice way or helper to achieve this. Any ideas?

Answer 1

I think the cleanest way to do this is by using a subquery join:
$latestContacts = Contact::select('customer_id',DB::raw('max(contacted_at) as latest_contact'))->groupBy('customer_id');
$query = Customer::select('customers.*', 'latest_contacts.latest_contact')
->joinSub($latestContacts, 'latest_contacts', function ($join){
$join->on([['customer.id', 'latest_contacts.customer_id']]);
})
->orderBy('latest_contacts.latest_contact')
->get();
More info: https://laravel.com/docs/8.x/queries#subquery-joins

Answer 2

I suspect there is an issue with your migration, the foreign key constraint is defined like this:
Check the documentation:
https://laravel.com/docs/8.x/migrations#foreign-key-constraints
Method 1: define foreign key constraint
public function up()
{
Schema::create('contacts', function (Blueprint $table) {
$table->id();
$table->foreignId('consumer_id')->constrained();
$table->string('type');
$table->dateTime('contacted_at');
$table->timestamps();
$table->softDeletes();
});
}
Method 2: define foreign key constraint
public function up()
{
Schema::create('contacts', function (Blueprint $table) {
$table->id();
$table->unsignedBigInteger('customer_id');
$table->foreign('customer_id')->references('id')->on('customers');
$table->string('type');
$table->dateTime('contacted_at');
$table->timestamps();
$table->softDeletes();
});
}