Laravel 5.6 set migration nullable foreign id - laravel

Question

This error popup:
#1452 - Cannot add or update a child row: a foreign key constraint fails (`ltfrbr10infosystem`.`franchises`, CONSTRAINT `franchises_operator_id_foreign` FOREIGN KEY (`operator_id`) REFERENCES `operators` (`id`) ON DELETE CASCADE ON UPDATE CASCADE)
Laravel Migrration:
public function up()
{
Schema::create('franchises', function (Blueprint $table) {
$table->increments('id');
$table->integer('operator_id')->nullable()->unsigned();
$table->foreign('operator_id')->references('id')->on('operators')->onDelete('cascade')->onUpdate('cascade');
$table->string('case_number')->nullable();
$table->string('business_address')->nullable();
$table->date('date_granted')->nullable();
$table->date('expiry_date')->nullable();
$table->string('route_name')->nullable();
$table->string('deno')->nullable();
$table->integer('authorize_units')->nullable();
$table->string('remarks')->nullable();
$table->timestamps();
});
}
I have tried this but still it gives me error
$table->integer('operator_id')->nullable()->unsigned()->change();
I also tried this
$table->integer('operator_id')->unsigned()->default(null);
How do I make operator_id foreign key default to null?

Answer 1

If the data on your database is not important you could refresh your migrations and your database using
php artisan migrate:refresh
This will rollback and migrate all your migrations again. Make sure you wrote the down method right,
also, you migration should look like this:
public function up()
{
Schema::create('franchises', function (Blueprint $table) {
$table->increments('id');
$table->unsignedInteger('operator_id')->nullable();
$table->foreign('operator_id')->references('id')->on('operators')->onDelete('cascade')->onUpdate('cascade');
$table->string('case_number')->nullable();
$table->string('business_address')->nullable();
$table->date('date_granted')->nullable();
$table->date('expiry_date')->nullable();
$table->string('route_name')->nullable();
$table->string('deno')->nullable();
$table->integer('authorize_units')->nullable();
$table->string('remarks')->nullable();
$table->timestamps();
});
}
Other way to do it is creating a new migration like this:
public function up()
{
Schema::table('franchises', function (Blueprint $table) {
$table->unsignedInteger('operator_id')->nullable()->change();
});
}

Answer 2

I think you get this error because the record you are trying to insert contains a wrong value for the column operator_id. This value is not a correct operator id and is not null (it could be 0, "null" or empty string, ...)
Can you paste here the exact SQL query which rises this error ?

Answer 3

Add this inside up function and run php artisan migrate:refresh --seed
public function up(){
Schema::disableForeignKeyConstraints();
Schema::create('franchises', function (Blueprint $table) {
$table->increments('id');
$table->integer('operator_id')->unsigned()->nullable();
$table->foreign('operator_id')->references('id')->on('operators')->onDelete('cascade')->onUpdate('cascade');
$table->string('case_number')->nullable();
$table->string('business_address')->nullable();
$table->date('date_granted')->nullable();
$table->date('expiry_date')->nullable();
$table->string('route_name')->nullable();
$table->string('deno')->nullable();
$table->integer('authorize_units')->nullable();
$table->string('remarks')->nullable();
$table->timestamps();
});Schema::enableForeignKeyConstraints();}

Answer 4

you should use this
$table->foreign('operator_id')->references('id')->on('operators')->nullable()->onDelete('cascade')->onUpdate('cascade');