Laravel 5 hasManyThrough error

Question

I’m learning a lot about these eloquent relationships but I’m not quite there in my understanding.

I have three tables:

Candidates • id
• candidate_number
• givennames
• familyname
• dob • created_at
• updated_at

Results • id
• certificate_number
• candidate_id
• qualification_id
• created_at
• updated_at

Qualifications • id
• code
• title
• created_at
• updated_at

A candidate has many results and a qualification has many results. A result belongs to a qualification and a candidate. On the candidaes.show page I want to show what qualifications are related to that candidate using a hasManyThrogh relationship. Here are my models.

Candidates:

<?php namespace App;

use Illuminate\Database\Eloquent\Model;

class Candidate extends Model {

    protected $table = 'candidates';
    public $timestamps = true;


    public function result()
    {
        return $this->hasMany('App\Result');
    }

    public function qualification()
    {
        return $this->hasManyThrough('App\Qualification', 'App\Result');
    }
}

Result Model:

<?php namespace App;

use Illuminate\Database\Eloquent\Model;

class Result extends Model {

   protected $table = 'results';
   public $timestamps = true;

   public function candidate()
   {
      return $this->belongsTo('App\Candidate');
   }

   public function qualification()
   {
      return $this->belongsTo('App\Qualification');
   }

}

Qualification Model:

<?php namespace App;

use Illuminate\Database\Eloquent\Model;

class Qualification extends Model {

   protected $table = 'qualifications';
   public $timestamps = true;

   public function result()
   {
      return $this->hasMany('App\Result');
   }

   public function candidate()
   {
      return $this->hasManyThrough('App\Candidate', 'App\Result');
   }
}

In my candidate controller:

public function show($id)
{
    $candidate = Candidate::with('qualification')->find($id);

    return view('candidates.show', compact('candidate'));
}

and in my view:

@extends('app')

@section('content')

    <h1>{{ $candidate->givennames }} {{ $candidate->familyname }}</h1>

    <div class="body"> {{ $candidate->dob }} </div>

    <div class="body"> {{ $candidate->candidate_number }} </div>

    <h3> Centre </h3>


    <h3> Qualifications </h3>

    @foreach($candidate->qualification as $qualification)

        <div class="body"> {{ $qualification->title }} </div>

    @endforeach

@stop

However it is retuning the following error:

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'qualifications.result_id' in 'on clause' (SQL: select qualifications.*, results.candidate_id from qualifications inner join results on results.id = qualifications.result_id where results.candidate_id in (17))

Can anyone help me or point me in the right direction? I’m not even sure I am doing the right thing with a hasManyThrough.

Answer 1

If a result has many Qualifications then a foreign key needs to be placed on the Qualification Table. Like so:

$table->integer('result_id')->unsigned();
$table->foreign('result_id')->references('id')->on('results');

You don't need to delete the table to add this. Just go to your terminal and create a new migration file

php artisan make:migration edit_qualification_table --table=qualifications

Then add these within the up function. Same with down so if you do delete the table these will be deleted too.