为什么在 Laravel 5.8 中创建外键失败?

Why is creating Foreign Key in Laravel 5.8 failing?(为什么在 Laravel 5.8 中创建外键失败?)

问题描述

下面的迁移脚本在旧版本的 Laravel 中运行流畅，但我将它添加到我的新 Laravel 5.8 中并运行了脚本.我收到错误:外键未正确形成

The migration script below was running smoothly in an older version of Laravel but I added it to my fresh Laravel 5.8 and ran the script. I'm getting Error: foreign key was not formed correctly

评估迁移:

public function up() { 
    Schema::create('evaluation', function (Blueprint $table) { 
        $table->increments('id'); 
        $table->integer('user_id')->unsigned()->index(); 
        $table->timestamps();
        $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
    });
}

用户迁移:

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

推荐答案

正如我们在上面的评论中所讨论的，外键列必须与它引用的主键具有相同的数据类型.

As we discussed in the comments above, a foreign key column must be the same data type as the primary key it references.

您将您的 user.id 主键声明为 $table->bigIncrements('id')，它变成了 BIGINT UNSIGNED AUTO_INCREMENTMySQL 语法.

You declared your user.id primary key as $table->bigIncrements('id') which becomes BIGINT UNSIGNED AUTO_INCREMENT in MySQL syntax.

您必须将外键声明为 $table->unsignedBigInteger('user_id') 这将在 MySQL 中变为 BIGINT UNSIGNED，使其与作为外键兼容user.id 列的键.

You must declare the foreign key as $table->unsignedBigInteger('user_id') which will become BIGINT UNSIGNED in MySQL, making it compatible with being a foreign key to the user.id column.

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