无法删除或更新 Laravel 中的项目

Question

when i tried delete item in laravel i get this message

SQLSTATE[23000]: Integrity constraint violation: 1451 Cannot delete or update a parent row: a foreign key constraint fails ( larblog . comments , CONSTRAINT comments_article_id_foreign FOREIGN KEY ( article_id ) REFERENCES articles ( id )) (SQL: delete from articles where id = 2)

this my delete function

 public function DeleteArticle($id){
        $article = Article::find($id);
        $article->delete();
        return redirect("article");
    }

this create articles table code

<?php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateArticle extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('articles', function (Blueprint $table) {
            $table->increments('id');
            $table->string('title');
            $table->text('body');
            $table->timestamps();
            $table->integer('user_id')->unsigned();
            $table->foreign('user_id')->references('id')->on('users');

        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('articles');
    }
}

and this create comments table code

<?php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateComments extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('comments', function (Blueprint $table) {
            $table->increments('id');
            $table->text('comment');
            $table->timestamps();
            $table->integer('article_id')->unsigned();
            $table->foreign('article_id')->references('id')->on('articles');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('comments');
    }
}

Iam tried to use this solution but did not work

$table->foreign('article_id')->references('id')->on('articles')->onUpdate('cascade')- 
>onDelete('cascade');

Answer 1

as you know your comments depends on articles once a article is delete then comment's relation going to break so either you first delete all comment's of that artical or set foreign key null to all the comment for that article
so that why you need to update your mygration with

$table->foreign('article_id')->references('id')->on('articles')->onDelete('cascade');

or

$table->integer('article_id')->unsigned()->nullable();

$table->foreign('article_id')->references('id')->on('articles')->onDelete('set null');