Question 63858 in PhpMyAdmin Question posted in
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why foreign key not get setted in laravel migrations – Phpmyadmin

I made an exam-question relationship, every exam has less than 200 questions, but when I run migrations, I go to the PHPMyAdmin and I don’t find the foreign key set, it’s only a bigint(20) unsigned column and not linked to the exams table.

exam model

<?php

namespace AppModels;

use AppModelsQuestion;
use IlluminateDatabaseEloquentModel;
use IlluminateDatabaseEloquentFactoriesHasFactory;

class Exam extends Model
{
    use HasFactory;

    protected $fillable = [
        //
    ];

    public function questions(){
        return $this->hasMany(Question::class);
    }
}

question model

<?php

namespace AppModels;

use AppModelsExam;
use IlluminateDatabaseEloquentModel;
use IlluminateDatabaseEloquentFactoriesHasFactory;

class Question extends Model
{
    use HasFactory;

    function exam(){
        return $this->belongsTo(Exam::class);
    }
}

exam migration

<?php

use IlluminateSupportCarbon;
use IlluminateSupportFacadesSchema;
use IlluminateDatabaseSchemaBlueprint;
use IlluminateDatabaseMigrationsMigration;

class CreateExamsTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('exams', function (Blueprint $table) {
            $table->id();
            $table->string('examHash')->unique();
            //..
            $table->timestamps();
        });
    }

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

questions migrations

<?php

use IlluminateDatabaseMigrationsMigration;
use IlluminateDatabaseSchemaBlueprint;
use IlluminateSupportFacadesSchema;

class CreateQuestionsTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('questions', function (Blueprint $table) {
            $table->id();
            $table->foreignId('exam_id')->constrained();
            $table->timestamps();
        });
    }

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

I’ve tried to:

Use this

$table->foreign('exam_id')->references('id')->on('exams');

but

Key column ‘exam_id’ doesn’t exist in table

EDIT:
it can be caused because my engine is not InnoDB, regularly I change the engine to InnoDB to create foreign keys

Tags:

3

Answers


  1. Chosen as BEST ANSWER
    0

    the problem as I've mentioned in the question is in the engine. so I wrote

    $table->engine = 'InnoDB';

    in both of question and exam tables...


  2. 0

    The method foreignId will only create an UNSIGNED BIGINT and not a foreign key constraint. To also create a constraint you need to call constrained() afterward.
    Try this:

    Schema::create('questions', function (Blueprint $table) {
            $table->id();
            $table->foreignId('exam_id')->constrained();
            $table->timestamps();
        });

    You can also find more information in the documentation.

    Login or Signup to reply.
  3. 0

    Try to add the constrained method when you define the foreign key in question’s migration, change:

    $table->foreignId('exam_id');

    to:

    $table->foreignId('exam_id')->constrained();
    Login or Signup to reply.
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