Laravel中的多联接表

Question

I have 4 tables below :

track

+----+-----+----------------+-------+
| ID | TID |     TITLE      | ALBUM |
+----+-----+----------------+-------+
|  1 | AAA | Yesterday      |     1 |
|  2 | BBB | Happy          |     2 |
|  3 | CCC | Gangname Style |     3 |
+----+-----+----------------+-------+

album

+----+-----+---------+-------+
| ID | AID |  TITLE  | COVER |
+----+-----+---------+-------+
|  1 | AAA | Album A | 1.jpg |
|  2 | BBB | Album B | 2.jpg |
|  3 | CCC | Album C | 3.jpg |
+----+-----+---------+-------+

track_artist

+----+-----+-----------+
| ID | TID | ARTIST_ID |
+----+-----+-----------+
|  1 |   1 |         1 |
|  2 |   2 |         2 |
|  3 |   3 |         3 |
+----+-----+-----------+

artist

+----+--------+--------+
| ID |  NAME  | AVATAR |
+----+--------+--------+
|  1 | Taylor | 1.JPG  |
|  2 | T-ara  | 2.JPG  |
|  3 | M2M    | 3.JPG  |
+----+--------+--------+

I want to get track.TITLE , album.TITLE and artist.NAME base on track.TID ( where TID = $XXX ) in 4 table above. It's easy when I use raw INNER JOIN MySQL code, but I want to use Eloquent ORM in Laravel. How I can do this ? Thank you.

I have analyzed :

One track belongsTo one Album

One track hasMany track_artist

One track_artist hasOne artist

One track hasMany artist

Answer 1

First, your relations ( in my opinion ) need some changes.

• One track belongs to one album and one album has many tracks (one to many)
• One track has one artist and one artist has multiple tracks (one to many)
• One album has multiple artist and one artist has multiple albums(many to many)

You will need a table for the many to many relation with the album id and the artist id

This is an example considering the above points

---

<?php
namespace App;
use Illuminate\Database\Eloquent\Model;

class track extends Model{
    function album(){
        $this->belongsTo(album::class);
    }
    function artist(){
        $this->belongsTo(artist::class);
    }
}

class album extends Model{
    function track(){
        $this->hasMany(track::class);
    }
    function artist(){
        $this->belongsToMany(artist::class, 'my_many_to_many_table');
    }
}

class artist extends Model{
    function track(){
        $this->hasMany(track::class);
    }
    function album(){
        $this->belongsToMany(album::class, 'my_many_to_many_table');
    }
}

Answer 2

You can try this

The table should be like this, you need 4 tables

albums(id, title, cover)
artist(id, name, avatar)
tracks(id, album_id, title)
track_artists (id, artist_id, track_id) ManyToMany with tracks

Models

class Album extends Model{

    function tracks(){
        $this->hasMany(Track::class);
    }
}

class Artist extends Model{

   function tracks(){
      $this->belongsToMany(Track::class, 'track_artists'); //here track_artists table is as pivot table
   }   
}

class Track extends Model{

   function album(){
        $this->belongsTo(Album::class);
   }

   function artist(){
      $this->belongsToMany(Artist::class, 'track_artists'); //here track_artists table is as pivot table
   }   
}

Fetch Data

$track = Track::with('album','artists')->find($trackId);

echo $track->title." - ". $track->album->title;
//now print all artist of this track
foreach($track->artists as $artist){
   echo $artist->name;
}

Note: You don't need to create model for track_artists because it is a pivot table for tracks and artists tables. You can insert and update in pivot table using Track or Artist laravel eloquent model. Though if you want you can create it extending Pivot .

Save Data in pivot table

$track = Track::find(1);
$artist = Artist::create(['name' => 'Katy Perry', 'avatar' => 'Katy_Perry.jpg']);
$track->artists()->save($artist); //this save track and artist relation in track_artists pivot table

For details https://laravel.com/docs/5.6/eloquent-relationships#many-to-many