How to define a protected $primaryKey property for composite key

https://github.com/laravel/framework/issues/5517

Eloquent doesn't support composite keys

You can define in your migration table as well,

     $table->string('Military_No')->primary();
     $table->string('classification_code')->primary();

Yeah, in the migration because the database supports it. But you can't use it in Eloquent models because Eloquent doesn't support it.

so i can't use laravel relationship with this model, right ?

Try this.

// Migration
$table->string('Military_No')->primary();
$table->string('classification_code')->primary();
$table->string('military_no_classification_code')
    ->virtualAs('concat(Military_No,classification_code)')
    ->index();

// Military Model 
protected $primaryKey = 'military_no_classification_code';

You can change de primaryKey on the fly.

Military::find('xxxxyyyy'); // military_no_classification_code

$military = (new Military)->setKeyName('Military_No');
$military->find('xxxx'); // military_no 

$military = (new military)->setKeyName('classification_code');
$military->find('yyyy'); // classification_code 

Relationships

// App\Military.php
function weaponsByMilitaryNo() {
      return $this->hasMany(App\Weapon::class, 'Military_No', 'Military_No');
}

function weaponsByClassificationCode() {
      return $this->hasMany(App\Weapon::class, 'classification_code', 'classification_code');
}

function weaponsByCompositeKeys() {
      return $this->hasMany(
        App\Weapon::class,
        'military_no_classification_code',
        'military_no_classification_code'
       );
}

setKeyName

https://github.com/laravel/framework/blob/5.8/src/Illuminate/Database/Eloquent/Model.php#L1326

Mysql VirtualAs

https://laravel.com/docs/master/migrations#column-modifiers

https://github.com/laravel/framework/blob/5.8/src/Illuminate/Database/Schema/Grammars/MySqlGrammar.php#L870

@pciranda Thank you i will try this :)

Not sure why you would need to do this when you can specify the key for route model binding, and you can create a unique index on those two columns.

Anyway, if you are using anything other than incrementing primary key, you need to add to your model

protected $incrementing=false;

It's worth checking out the thiagoprz/eloquent-composite-key package which extends Eloquent with composite key support.

https://github.com/thiagoprz/eloquent-composite-key