テーブルを紐づける

[vagrant@localhost laravel]$ php artisan make:model Document –migration
Model created successfully.
Created Migration: 2018_09_22_220524_create_documents_table

public function up()
    {
        Schema::create('documents', function (Blueprint $table) {
            $table->increments('id');
            $table->unsignedInteger('article_id'); // articleのid
            $table->string('body');
            $table->timestamps();
            $table->foreign('article_id')->references('id')->on('articles')->onDelete('cascade');
        });
    }

コーディングと設計は使う脳みそが違いますね。先に設計をつくっておかないと、思いつきの適当なサービスになってしまいますな。
dateが型がよくわかりません。timestampsだと、yyyymmdd hh:mm:ssになりそうで。

public function up()
    {
        Schema::create('documents', function (Blueprint $table) {
            $table->increments('id');
            $table->unsignedInteger('article_id'); // articleのid
            $table->string('mobile');
            $table->string('published_at');
            $table->text('body');
            $table->timestamps();
            $table->foreign('article_id')->references('id')->on('articles')->onDelete('cascade');
        });
    }

migrateします。
[vagrant@localhost laravel]$ php artisan migrate
Migrating: 2018_09_22_220524_create_documents_table
Migrated: 2018_09_22_220524_create_documents_table

belong to

namespace App;

use Illuminate\Database\Eloquent\Model;

class Document extends Model
{
    //
    protected $fillable = ['mobile','published_at','body'];

    public function article(){
    	return $this->belongsTo('App\Article')
    }

}

article.phpの方

class Article extends Model
{
    //
    protected $fillable = ['login_id','role','name','password','mail','test_mail','updated_person'];

    public function documments(){
    	return $this->hasMany('App\Document')
    }
}

紐づけはできたっぽい
いけるもんだ。