SQLSTATE[HY000]：一般錯誤：1215 無法添加外鍵約束（Laravel）

Question

我不斷收到此錯誤。 我知道這是外鍵的問題，但我真的無法理解它不能正常工作的原因。 我正在嘗試與橋接表建立多對多關系。 請，如果你能幫我解決這個問題！ 在這里你可以看到遷移：

餐桌禮服：

<?php

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

class Dress extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('dresses', function (Blueprint $table) {
            $table->id();
            $table->unsignedBigInteger('dress_id');
            $table->string('name')->unique();
            $table->string('brand');
            $table->decimal('price');
            $table->string('fabric');
            $table->string('size');
            $table->string('type');
            $table->string('wash_instruction');
            $table->string('product_details');
            $table->string('fit');
            $table->rememberToken();;
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        //
    }
}

表願望清單：

<?php

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

class Wishlist extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('wishlists', function (Blueprint $table) {
            $table->id();
            $table->unsignedBigInteger('wishlist_id');
            $table->foreign('wishlist_id')
                ->references('user_id')
                ->on('users')->onDelete('cascade');
        });
    }



    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        //
    }
}

橋表：

<?php

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

class CreateWishlistDressTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('wishlist_dress', function (Blueprint $table) {
            $table->id();
            $table->unsignedBigInteger('dress_id');
            $table->foreign('dress_id')
                ->references('id')
                ->on('dresses')->onDelete('cascade');

            $table->unsignedBigInteger('wishlist_id');
            $table->foreign('wishlist_id')
                ->references('id')
                ->on('wishlists')->onDelete('cascade');

            $table->timestamps();
        });
    }

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

Answer 1

您的用戶遷移是如何設置的？ 用戶遷移文件中有名為 users_id 的列嗎？

通常只使用 id 列，它是從 users 遷移文件中的$table->id()生成的。 我相信如果您從users_id更改為id ，您的遷移應該可以工作，如下所示：

<?php

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

class Wishlist extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('wishlists', function (Blueprint $table) {
            $table->id();
            $table->unsignedBigInteger('wishlist_id');
            $table->foreign('wishlist_id')
                ->references('id') //Changed from user_id to id
                ->on('users')->onDelete('cascade');
        });
    }



    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        //
    }
}