Laravel - Eloquent ORM关系查询

Question

I have 5 tables:

 1. news
 2. tags
 3. filters
 4. news_tag
 5. tag_filters

The tables structure are as follows:

news

id
title
description

tags

id
title

filters

id
title

news_tag

id
tag_id
news_id

tag_filter

id
tag_id
filter_id

Let's say for example my tables have the following records:

news: id = 1 title = News_1 Description = Details for News_1
tags: id = 1 title = PHP
filters: id = 1 title = PHP News
news_tag: id = 1 tag_id = 1 news_id = 1
tag_filter: id = 1 tag_id = 1 filter_id = 1

The relationships in my models are as follows:

News model

public function tags(){

    return $this->belongsToMany('App\Tag', 'news_tag');
}

Tag model

public function news(){

    return $this->belongsToMany('App\News', 'news_tag');
} 

public function filters(){

    return $this->belongsToMany('App\Filter', 'tag_filter');
}

Filter model

public function tags(){

    return $this->belongsToMany('App\Tag', 'tag_filter');
}

Let's say my route is as follows: Route::get('news/filter/{filter_id}','NewsController@getNews');

I want to retrieve all the news related to tag_id 1 when I pass filter_id 1 to my route. Anyone can help me how to do this in my controller?

Answer 1

There is no simple way to do this, but you can use something like this:

News::select("news.*")
  ->join('tags'...)
  ->join('filters'...)
  ->where('filter_id',...)
  ->where('tag_id',...)
  ->get();

Note select() instruction. If you skip it, Laravel will load invalid fields into your News models. It's must-have when you do joins in Eloquent Builder.

If you want to eager load relations in this case, use with() method of the query builder.

Answer 2

You can try some nested whereHas instead of join. I'm not sure about performance.

    $filterId = 1;
    News::whereHas('tags', function($q1) use ($filterId) {
        $q1->whereHas('filters', function($q2) use ($filterId) {
            $q2->where('id', '=', $filterId);
        });
    });