如何在 Laravel 迁移中使用多个数据库设置外键约束

Question

I'm currently working on a project that requires using multiple databases. In my .env file I have the following database variables:

DB_CONNECTION=mysql
DB_ONE_NAME=db1

DB_CONNECTION_TWO=mysql2
DB_TWO_NAME=db2

In my config/database.php file I have the following reference:

'mysql' => [
        'driver' => 'mysql',
        'url' => env('DATABASE_URL'),
        'host' => env('DB_HOST', '127.0.0.1'),
        'port' => env('DB_PORT', '3306'),
        'database' => env('DB_ONE_NAME', 'db1'),
        'username' => env('DB_USERNAME', 'user'),
        'password' => env('DB_PASSWORD', 'root'),
        'unix_socket' => env('DB_SOCKET', ''),
        'charset' => 'utf8',
        'collation' => 'utf8_general_ci',
        'prefix' => '',
        'prefix_indexes' => true,
        'strict' => true,
        'engine' => 'InnoDB',
        'options' => extension_loaded('pdo_mysql') ? array_filter([
            PDO::MYSQL_ATTR_SSL_CA => env('MYSQL_ATTR_SSL_CA'),
        ]) : [],
    ],

'mysql2' => [
        'driver' => 'mysql',
        'url' => env('DATABASE_URL'),
        'host' => env('DB_HOST', '127.0.0.1'),
        'port' => env('DB_PORT', '3306'),
        'database' => env('DB_TWO_NAME', 'db2'),
        'username' => env('DB_USERNAME', 'user'),
        'password' => env('DB_PASSWORD', 'root'),
        'unix_socket' => env('DB_SOCKET', ''),
        'charset' => 'utf8',
        'collation' => 'utf8_general_ci',
        'prefix' => '',
        'prefix_indexes' => true,
        'strict' => true,
        'engine' => 'InnoDB',
        'options' => extension_loaded('pdo_mysql') ? array_filter([
            PDO::MYSQL_ATTR_SSL_CA => env('MYSQL_ATTR_SSL_CA'),
        ]) : [],
    ],

In my first migration file, I have this:

<?php

    use Illuminate\Database\Migrations\Migration;
    use Illuminate\Database\Schema\Blueprint;
    use Illuminate\Support\Facades\Schema;

    class CreateUsersTable extends Migration
    {
  
      public function up()
      {
        Schema::connection('mysql')->create('users', function (Blueprint $table) {
          $table->id();
          $table->string('name');
          $table->string('email')->unique();
          $table->string('username')->unique();
          $table->timestamps();

          $table->index('id');

    });
}


    public function down()
    {
      Schema::connection('mysql')->dropIfExists('users');
    }
}

In the second migration table I have this:

<?php

    use Illuminate\Database\Migrations\Migration;
    use Illuminate\Database\Schema\Blueprint;
    use Illuminate\Support\Facades\Schema;

    class CreateProjectsTable extends Migration
    {
  
      public function up()
      {
        Schema::connection('mysql2')->create('projects', function (Blueprint $table) {
          $table->id();
          $table->foreignId('user_id')->nullable()->constrained('mysql.users')->onDelete('set null');
          $table->string('name')->unique();
          $table->timestamps();

          $table->index(['id', 'user_id']);

    });
}


    public function down()
    {
      Schema::connection('mysql2')->dropIfExists('projects');
    }
}

What could I be doing wrong? I've checked for any duplicate files but couldn't find any errors whatsoever.

Again, I recently upgraded both PHP and MYSQL to their recent versions on my machine. All the extensions needed/required to work on a Laravel project are all installed correctly.

But still, I'm getting this error:

SQLSTATE[HY000]: General error: 1005 Can't create table `db2`.`projects` (errno: 150 "Foreign key constraint is incorrectly formed") (SQL: alter table `projects` add constraint `projects_user_id_foreign` foreign key (`user_id`) references `mysql`.`users` (`id`) on delete set null)

Also, when I run this command,

php artisan migrate --pretend

Or

php artisan migrate

I still get the same error.

I have also tried using this:

$table->unsignedBigInteger('user_id')->nullable();
$table->foreign('user_id')->references('id')->on('mysql.users')->onDelete('set null');

but nothing is working. Is there another way to go about this? If there is, please give me suggestions. Thanks for your time.

Answer 1

So after like 14 hours of testing with different kinds of methods, I ended up with what I call "You should have known hack" lol 😂

I was using the second database connection name inside of the migration table rather than using the database name.

My initial code where I used the connection name on the foreign key:

  Schema::connection('mysql2')->create('projects', function (Blueprint $table) {
      $table->id();
      $table->foreignId('user_id')->nullable()->constrained('mysql.users')->onDelete('set null');
      $table->string('name')->unique();
      $table->timestamps();

      $table->index(['id', 'user_id']);
  });

What works now! using the database name and not the connection name on the foreign key:

 Schema::connection('mysql2')->create('projects', function (Blueprint $table) {
      $table->id();
      **$table->foreignId('user_id')->nullable()->constrained('db1.users')->onDelete('set null');**
      $table->string('name')->unique();
      $table->timestamps();

      $table->index(['id', 'user_id']);
  });

So, the second option works fine. I hope this helps someone too!!!