MySQL

Question

我已经在Laravel迁移中看到了与此错误相关的其他问题，但找不到解决方案。也许我错过了一些基本的东西。

按顺序，我的迁移是：

• 用户
• password_resets
• 类别
• - 行业标准
• 服务

一个类别有很多sub_categories，它有很多服务。

所以这就是我在迁移文件中写的内容：

分类

class CreateCategoriesTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('categories', function (Blueprint $table) {
            $table->increments('id');
            $table->timestamps();

            $table->string('name', 100);
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('categories');
    }
}

子类别：

class CreateSubCategoriesTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('sub_categories', function (Blueprint $table) {
            $table->increments('id');
            $table->timestamps();

            $table->string('name', 100);
            $table->integer('category_id')->unsigned();

            $table->foreign('category_id')->references('categories')
                    ->on('id')->onDelete('cascade');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('sub_categories');
    }
}

服务：

class CreateServicesTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('services', function (Blueprint $table) {
            $table->increments('id');
            $table->timestamps();

            $table->string('name', 100);
            $table->integer('sub_category_id')->unsigned();

            $table->foreign('sub_category_id')->references('sub_categories')
                    ->on('id')->onDelete('cascade');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('services');
    }
}

在php artisan migrate，我得到以下内容：

 [Illuminate\Database\QueryException]                                                                     
  SQLSTATE[HY000]: General error: 1005 Can't create table 'servoapp.#sql-b79_34' (errno: 150) (SQL: alter  
   table `sub_categories` add constraint `sub_categories_category_id_foreign` foreign key (`category_id`)  
   references `id` (`categories`) on delete cascade)                                                       

 [PDOException]                                                                               
  SQLSTATE[HY000]: General error: 1005 Can't create table 'servoapp.#sql-b79_34' (errno: 150)  

我无法弄清楚我做错了什么。请帮忙！

Answer 1

更改

$table->foreign('sub_category_id')->references('sub_categories')
                    ->on('id')->onDelete('cascade');

到

$table->foreign('sub_category_id')->references('id')
                    ->on('sub_categories')->onDelete('cascade');

和

$table->foreign('category_id')->references('id')->on('categories')->onDelete('cascade');

像这样的两个模式上的

：

子类别：

class CreateSubCategoriesTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('sub_categories', function (Blueprint $table) {
            $table->increments('id');
            $table->timestamps();

            $table->string('name', 100);
            $table->integer('category_id')->unsigned();

            $table->foreign('category_id')->references('id')
                    ->on('categories')->onDelete('cascade');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('sub_categories');
    }
}

服务

class CreateServicesTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('services', function (Blueprint $table) {
            $table->increments('id');
            $table->timestamps();

            $table->string('name', 100);
            $table->integer('sub_category_id')->unsigned();

            $table->foreign('sub_category_id')->references('id')
                    ->on('sub_categories')->onDelete('cascade');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('services');
    }
}