Foreign Key on Laravel Migration causing General Error 1215

Question

I'm trying to create multiple tables with foreign keys using Laravels migration. I have a problems migration table like so

Schema::create('problems', function($table)
        {
            $table->increments('id');
            $table->integer('created_by')->unsigned();
            $table->foreign('created_by')->references('id')->on('users');
            $table->integer('category')->unsigned();
            $table->foreign('category')->references('id')->on('categories');
            $table->timestamps();
        });

A categories migration

Schema::create('categories', function($table)
        {
            $table->increments('id');
            $table->string('category_name');
            $table->timestamps();
        });

My first foreign key into the users migration works fine but as soon as it hits the foreign key for the category id, it gives a

SQLSTATE HY000 General Error 1215 Impossible d'ajouter des contraintes d'index externe (SQL; alter table 'problems' add constraint problems_category_foreign foreign key ('category') references 'categories' ('id'))

(I can't properly read the French and I don't know why it gives me errors in French. I have not been able to find a way to change it as I am not French, nor can I understand it)

I don't understand why this would work for one and not the other when they are essentially the same thing.

Answer 1

You need to make sure that the order of the migration files work out. For example, you cannot create a problems table with a foreign key that references id on categories table before you actually create the categories table itself.

For the french error problem, look at this question.