Laravel迁移创建自定义外键

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

class CreatePostsTable extends Migration
{
    public function up()
    {
        Schema::create('posts', function (Blueprint $table) {
            $table->increments('id');
            $table->string('title');
            $table->text('content');
            $table->unsignedInteger('user_id'); // 添加 user_id 字段

            // 创建自定义外键约束
            $table->foreign('user_id')
                  ->references('id')
                  ->on('users')
                  ->onDelete('cascade') // 当用户被删除时，相关的帖子也会被删除
                  ->onUpdate('cascade'); // 当用户的 ID 更新时，相关的帖子的 user_id 也会更新
        });
    }

    public function down()
    {
        Schema::dropIfExists('posts');
    }
}

// 确保数据库引擎为 InnoDB
Schema::table('posts', function (Blueprint $table) {
    $table->engine = 'InnoDB';
});

// 示例：允许 user_id 为空
$table->unsignedInteger('user_id')->nullable();