update content of stored column in laravel controller

I have a table with 3 columns: firstname lastname fullname

in migration:

Schema::create('owners', function (Blueprint $table) {
 $table->id(); 
$table->string('firstname',20);
 $table->string('lastname', 20);
 $table->string('fullname')->storedAs('CONCAT(firstname,lastname)');
 $table->timestamps(); 
});

the problem is that i want to change the concatenation order in the controller i tried to use db statement but it doesn't work

-in the controller:

$owners= Owner::findOrFail($id);
$owners->update([
'firstname'=>$request['firstname'],
 'lastname' =>$request['lastname'],
 ]); 
DB::statement('UPDATE owners SET fullname AS CONCAT(lastname,firstname) STORED WHERE ID=1 ');

I don't want to just use a simple concatenation because the user can change the firstname or the lastname and the order that's why I used storedAs()

any ideas please?

via Chebli Mohamed