外键代码在 Laravel 8 的迁移中不起作用

Question

我尝试创建一个外键，但是它不起作用。

帖子迁移

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

class CreatePostsTable extends Migration
{
    public function up()
    {
        Schema::create('posts', function (Blueprint $table) {
            $table->id();
            $table->string("title", 60);
            $table->string("description", 200);
            $table->text("content");
            $table->string("photo");
            $table->unsignedBigInteger('user_id');
            $table->timestamps();
            $table->foreign("user_id")->references("id")
                ->on("users")->onDelete("cascade");
        });
    }
    
    public function down()
    {
        Schema::dropIfExists('posts');
    }
}

用户迁移

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

class CreateUsersTable extends Migration
{
    public function up()
    {
        Schema::create('users', function (Blueprint $table) {
            $table->id();
            $table->string("name", 30);
            $table->string("email")->unique();
            $table->string("password");
            $table->string("username")->unique();
            $table->timestamps();
        });
    }
    
    public function down()
    {
        Schema::dropIfExists('users');
    }
}

我正在尝试为应该通过外键与用户 ID 连接的帖子创建一个“user_id”列。但是，当我迁移时，出现如下错误

Illuminate\Database\QueryException

SQLSTATE[HY000]: General error: 1005 Can't create table mytest_db.posts (errno: 150 "Foreign key constraint is incorrectly formed") (SQL: alter table posts add constraint posts_user_id_foreign foreign key (user_id) references users (id) on delete cascade)

at W:\domains\mytest.uz\vendor\laravel\framework\src\Illuminate\Database\Connection.php:678 674▕ // If an exception occurs when attempting to run a query, we'll format the error 675▕ // message to include the bindings with SQL, which will make this exception a 676▕ // lot more helpful to the developer instead of just the database's errors. 677▕ catch (Exception $e) { ➜ 678▕ throw new QueryException( 679▕ $query, $this->prepareBindings($bindings), $e 680▕ ); 681▕ } 682▕

1
W:\domains\mytest.uz\vendor\laravel\framework\src\Illuminate\Database\Connection.php:471 PDOException::("SQLSTATE[HY000]: General error: 1005 Can't create table mytest_db.posts (errno: 150 "Foreign key constraint is incorrectly formed")")

2
W:\domains\mytest.uz\vendor\laravel\framework\src\Illuminate\Database\Connection.php:471 PDOStatement::execute()

Answer 1

不能在尚不存在的表上定义外键。

Laravel 按文件名顺序执行迁移，在迁移名称前加上时间戳。确保 CreatePostsTable 迁移在之后迁移 CreateUsersTable。

外键代码在 Laravel 8 的迁移中不起作用

Foreign key codes are not working in migrations of Laravel 8

php

mysql

foreign-keys

laravel

laravel-8