php - 错误号 : 150 "Foreign key constraint is incorrectly formed" but check everything I know

Question

问题

运行迁移时，最后一个表的标题中出现错误。

我的数据库是本地MySQL。

错误

Illuminate\Database\QueryException : SQLSTATE[HY000]: General error: 1005 Can't create table shopping_list_develop.#sql-1698_2b (errno: 150 "Foreign key constraint is incorrectly formed") (SQL: alter table products add constraint products_shopping_list_id_foreign foreign key (shopping_list_id) references shopping_lists (id) on delete set null on update cascade)

已经尝试过

这是我检查的:

• 父表 (shopping_lists) 在子表 (products) 之前创建。
• 外键 shopping_list_id 与其引用的列具有相同的类型。
• shopping_lists 和 products 这两个表具有相同的数据库引擎 (InnoDB)。

我已阅读其他答案，但找不到解决方案。

迁移

2019_05_13_192170_create_shopping_lists_table.php

<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Carbon\Carbon;

class CreateShoppingListsTable extends Migration {

    public function up()
    {
        Schema::create('shopping_lists', function(Blueprint $table) {
            $table->bigIncrements('id');
            $table->string('name')->nullable()->default(Carbon::now()->toDateString());
            $table->unsignedBigInteger('user_id');
            $table->timestamps();

            $table->foreign('user_id')->references('id')->on('users')
                        ->onDelete('cascade')
                        ->onUpdate('cascade');
        });
    }

    public function down()
    {
        Schema::table('shopping_lists', function(Blueprint $table) {
            $table->dropForeign(['user_id']);
        });
        Schema::dropIfExist('shopping_lists');
    }
}

2019_05_13_192700_create_products_table.php

<?php

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

class CreateProductsTable extends Migration {

    public function up()
    {
        Schema::create('products', function(Blueprint $table) {
            $table->bigIncrements('id');
            $table->string('name');
            $table->string('brand')->nullable()->default(null);
            $table->float('price', 6,2)->nullable()->default(null);
            $table->string('note')->nullable()->default(null);
            $table->string('salable_type');
            $table->unsignedBigInteger('salable_id');
            $table->unsignedBigInteger('shopping_list_id');
            $table->timestamps();

            $table->foreign('shopping_list_id')->references('id')->on('shopping_lists')
                        ->onDelete('set null')
                        ->onUpdate('cascade');
        });
    }

    public function down()
    {
        Schema::table('products', function(Blueprint $table) {
            $table->dropForeign(['shopping_list_id']);
        });

        Schema::dropIfExist('products');
    }
}

感谢您的帮助，如果需要，请向我询问任何额外信息。

Answer 1

在 2019_05_13_192700_create_products_table.php 迁移中，onDelete 将该值设置为 null。

$table->foreign('shopping_list_id')->references('id')->on('shopping_lists')
                        ->onDelete('set null')
                        ->onUpdate('cascade');

但是您声明的列不可为空

$table->unsignedBigInteger('shopping_list_id');

尝试通过执行以下操作使该列可为空:

$table->unsignedBigInteger('shopping_list_id')->nullable();