使用laravel创建外键会出现错误：无法添加外键约束

Question

我想添加两个表，一个产品表和一个类别表。然后我要将产品表中的一个类别id链接到类别表中的主键。下面是我的代码：

public function up()
{
    Schema::create('products', function (Blueprint $table) {
      $table->bigIncrements('id');
      $table->string('title');
      $table->string('imgpath');
      $table->text('description');
      $table->integer('price');
      $table->integer('hotItemNumber')->nullable();
      $table->timestamps();
      $table->softDeletes();
    });
}

public function up()
{
    Schema::create('categories', function (Blueprint $table) {
        $table->bigIncrements('id');
        $table->string('categroyName');
        $table->timestamps();
    });
}

public function up()
{
  Schema::table('products', function($table) {
    $table->integer('category_id')->unsigned()->index();
    $table->foreign('category_id')->references('id')->on('categories');
  });
}

SQLSTATE[HY000]:一般错误：1215无法添加外键约束(SQL:alter table产品添加约束products_categoryid_foreign外键(categoryid)引用category(id))

Answer 1

在新的迁移中，尝试更改类型，如下所示

public function up()
{
  Schema::table('products', function($table) {
    $table->bigInteger('category_id')->unsigned()->index();
    $table->foreign('category_id')->references('id')->on('categories');
  });
}

因为在categories表中，id的类型为bigincrements