我正在嘗試1:1在我的訪客和聯(lián)系人之間添加關(guān)系<?phpuse Illuminate\Database\Migrations\Migration;use Illuminate\Database\Schema\Blueprint;use Illuminate\Support\Facades\Schema;class AddRelationToVisitorsDRelationToVisitorsContacts extends Migration{    public function up()    {        Schema::table('contacts', function(Blueprint $table)        {            $table->bigInteger('visitor_id')->unsigned();            $table->foreign('visitor_id')->references('id')->on('visitors')->onDelete('cascade');        });    }    public function down()    {        Schema::table('contacts', function($table)        {            $table->dropForeign('contacts_visitor_id_foreign');            $table->dropColumn('visitor_id');        });        Schema::table('visitors', function(Blueprint $table)        {            $table->dropColumn('contact_id');        });    }}運(yùn)行時(shí)php artisan migrateMigrating: 2020_04_16_104641_update_contacts_table_04_16_2020