Eloquent - Cannot add foreign key constraint - sql

Question

Common question I guess, but I can't resolve it despite the informations I found online.
I've a sequence of hasMany relations :
User has many clients has many contracts has many materials.
I did my best but I find myself confronted to this error :
[Illuminate\Database\QueryException]
SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint
(SQL: create table clients (id int unsigned not null, user_id
int unsigne d null, ...) default character set utf8mb4 collate
utf8mb4_unicode_ci engine = InnoDB)
SQLSTATE[HY000]: General error: 1215 Cannot add foreign key
constraint
Migrations :
class CreateUsersTable extends Migration
{
public function up()
{
Schema::create('users', function (Blueprint $table) {
$table->engine = 'InnoDB';
// Keys
$table->increments('id');
// Other
...
$table->timestamps();
});
}
public function down()
{
Schema::disableForeignKeyConstraints();
Schema::dropIfExists('clients');
Schema::drop('users');
Schema::enableForeignKeyConstraints();
}
}
class CreateClientsTable extends Migration
{
public function up()
{
Schema::create('clients', function (Blueprint $table) {
$table->engine = 'InnoDB';
// keys
$table->unsignedInteger('id')->unique();
$table->primary('id');
$table->unsignedInteger('user_id')
->nullable();
$table->foreign('user_id')->references('id')->on('users')
->onDelete('cascade');
// others
...
});
}
public function down()
{
Schema::disableForeignKeyConstraints();
Schema::dropIfExists('contracts');
Schema::drop('clients');
Schema::enableForeignKeyConstraints();
}
}
class CreateContractsTable extends Migration
{
public function up()
{
Schema::create('contracts', function (Blueprint $table) {
$table->engine = 'InnoDB';
// Keys
$table->increments('id');
$table->string('contract_number')->unique();
$table->unsignedInteger('client_id');
$table->foreign('client_id')->references('id')->on('clients')
->onDelete('cascade');
// Others
...
});
}
public function down()
{
Schema::disableForeignKeyConstraints();
Schema::dropIfExists('materials');
Schema::drop('contracts');
Schema::enableForeignKeyConstraints();
}
}
class CreateMaterialsTable extends Migration
{
public function up()
{
Schema::create('materials', function (Blueprint $table) {
$table->engine = 'InnoDB';
// Keys
$table->increments('id');
$table->string('contract_number')->unique();
$table->unsignedInteger('contract_id');
$table->foreign('contract_id')->references('id')->on('contracts')
->onDelete('cascade');
// Others
...
});
}
public function down()
{
Schema::drop('materials');
}
}
What am I doing wrong ?

Answer 1

You should add ->unsigned() to all your key columns you have.
Please use this instead of unsignedInteger() and set the type to integer()

Answer 2

Are you sure that your migrations are running in the correct order? They should be running in the order you provided in your example code. I can't seem to recreate the error on my end using your exact example migrations.
The order is determined by the date at the beginning of the migration's filename. Alternatively, you could create all these tables in the same migration to force the order that way.