Php 删除带有外键 Laravel 错误的列：一般错误：1025 重命名错误

我使用如下迁移创建了一个表:

public function up()
{
    Schema::create('despatch_discrepancies',  function($table) {
        $table->increments('id')->unsigned();
        $table->integer('pick_id')->unsigned();
        $table->foreign('pick_id')->references('id')->on('picks');
        $table->integer('pick_detail_id')->unsigned();
        $table->foreign('pick_detail_id')->references('id')->on('pick_details');
        $table->integer('original_qty')->unsigned();
        $table->integer('shipped_qty')->unsigned();
    });
}

public function down()
{
    Schema::drop('despatch_discrepancies');
}

我需要更改此表并删除外键引用&amp；列pick_detail_id，并在pick_id列之后添加一个名为sku的新varchar列.

因此，我创建了另一个迁移，如下所示:

public function up()
{
    Schema::table('despatch_discrepancies', function($table)
    {
        $table->dropForeign('pick_detail_id');
        $table->dropColumn('pick_detail_id');
        $table->string('sku', 20)->after('pick_id');
    });
}

public function down()
{
    Schema::table('despatch_discrepancies', function($table)
    {
        $table->integer('pick_detail_id')->unsigned();
        $table->foreign('pick_detail_id')->references('id')->on('pick_details');
        $table->dropColumn('sku');
    });
}

运行此迁移时，我收到以下错误:

[Illumb\Database\QueryException]

[PDOException]
SQLSTATE[HY000]:常规错误:1025重命名时出错 ‘./dev_iwms_reboot/despatch_dispanciations’到 ‘./dev_iwms_reboot/#sql2-67c-17c464’(错误号:152)

当我试图通过运行php artisan migrate:rollback命令来逆转此迁移时，我收到一条Rolled back消息，但它实际上并没有在数据库中执行任何操作.

你知道可能出了什么问题吗？如何删除具有外键引用的列？