Laravel6迁移修改timestamp字段报未知列类型错误如何解决

问题场景 #

初始开发时创建work_schedule_times表，将start_time、end_time字段设置为time类型，初始迁移代码：

Schema::create('work_schedule_times', function (Blueprint $table) {
    $table->time('start_time');
    $table->time('end_time');
});

后续需要编写新迁移，将employee_work_schedules表的对应字段从time类型修改为timestamp类型，最初编写的修改迁移代码：

Schema::table('employee_work_schedules', function (Blueprint $table) {
    $table->timestamp('start_time')->change();
    $table->timestamp('end_time')->nullable()->change();
});

执行迁移命令时抛出如下错误：

Unknown column type "timestamp" requested. Any Doctrine type that you use has to be registered with \Doctrine\DBAL\Types\Type::addType(). You can get a list of all the known types with \Doctrine\DBAL\Types\Type::getTypesMap(). If this error occurs during database introspection then you might have forgotten to register all database types for a Doctrine Type. Use AbstractPlatform#registerDoctrineTypeMapping() or have your custom types implement Type#getMappedDatabaseTypes(). If the type name is empty you might have a problem with the cache or forgot some mapping information.

Laravel 9 官方提供的修复方案是在config/database.php中添加DBAL配置注册timestamp类型，但该方案依赖Laravel 9内置的Illuminate\Database\DBAL\TimestampType类，Laravel 6 无该类，无法直接使用。

适配Laravel 6的可行方案 #

前置检查 #

使用->change()方法修改字段前，必须先安装兼容版本的doctrine/dbal依赖，Laravel 6 最高兼容2.x版本，执行安装命令：

composer require doctrine/dbal:^2.0

禁止安装3.x及以上版本的dbal，会出现框架版本兼容问题

方案1：迁移内手动注册DBAL类型映射（推荐） #

报错核心原因是Laravel 6 依赖的doctrine/dbal 2.x版本没有内置timestamp的类型映射，直接在迁移文件的方法开头手动注册映射即可，不需要修改全局配置。
完整迁移代码示例：

<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Schema;
use Doctrine\DBAL\Types\Type;
use Doctrine\DBAL\Types\DateTimeType;

class ModifyEmployeeWorkSchedulesTimeFields extends Migration
{
    public function up()
    {
        // 注册timestamp类型映射
        if (!Type::hasType('timestamp')) {
            Type::addType('timestamp', DateTimeType::class);
        }
        DB::getDoctrineConnection()
            ->getDatabasePlatform()
            ->registerDoctrineTypeMapping('timestamp', 'datetime');

        Schema::table('employee_work_schedules', function (Blueprint $table) {
            $table->timestamp('start_time')->change();
            $table->timestamp('end_time')->nullable()->change();
        });
    }

    public function down()
    {
        // 回滚时也需要注册映射，否则回滚会报同样错误
        if (!Type::hasType('timestamp')) {
            Type::addType('timestamp', DateTimeType::class);
        }
        DB::getDoctrineConnection()
            ->getDatabasePlatform()
            ->registerDoctrineTypeMapping('timestamp', 'datetime');

        Schema::table('employee_work_schedules', function (Blueprint $table) {
            $table->time('start_time')->change();
            $table->time('end_time')->nullable()->change();
        });
    }
}

方案2：执行原生SQL修改字段（无依赖问题） #

如果不想处理DBAL类型映射逻辑，可以直接执行原生SQL语句完成字段修改，完全绕过->change()方法的依赖限制。

注意：原生SQL需要和当前使用的数据库类型匹配，以下示例为MySQL语法，使用其他数据库请自行调整字段修改语法，同时要和原有字段的非空、默认值属性保持一致，避免丢失字段配置。

<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Support\Facades\DB;

class ModifyEmployeeWorkSchedulesTimeFields extends Migration
{
    public function up()
    {
        DB::statement("
            ALTER TABLE employee_work_schedules 
            MODIFY COLUMN start_time TIMESTAMP NOT NULL,
            MODIFY COLUMN end_time TIMESTAMP NULL
        ");
    }

    public function down()
    {
        DB::statement("
            ALTER TABLE employee_work_schedules 
            MODIFY COLUMN start_time TIME NOT NULL,
            MODIFY COLUMN end_time TIME NULL
        ");
    }
}

内容的提问来源于stack exchange，提问作者hassan