Laravel Many-To-Many多对多关系模式示例详解

One-To-One //一对一
One-To-Many //一对多
Many-To-Many //多对多

User-To-Profile // One-To-One
User-To-Articles // One-To-Many
Articles-To-Tags // Many-To-Many

Schema::create('articles', function (Blueprint $table) {
            $table->increments('id');
            $table->string('title');
            $table->text('content');
            $table->timestamps();
        });

Schema::create('tags', function (Blueprint $table) {
            $table->increments('id');
            $table->string('name');
            $table->timestamps();
        });

Schema::create('article_tag', function(Blueprint $table) {
            $table->integer('article_id')->unsigned()->index();
            $table->foreign('article_id')->references('id')->on('articles')->onDelete('cascade');
            $table->integer('tag_id')->unsigned()->index();
            $table->foreign('tag_id')->references('id')->on('tags')->onDelete('cascade');
        });

public function tags()
    {
        return $this->belongsToMany('App\Tag');
    }

public function articles()
    {
        return $this->belongsToMany('App\Article');
    }

$article = Article::find($id);
dd($article->tags);

public function showArticleByTagName($name)
    {
        $tag = Tag::where('value','=',$name)->first();
        dd($tag->articles);
    }