How to change constraint FOREIGN KEY in mysql 8 from `ON DELETE CASCADE` to `ON DELETE SET NULL` in-CodePudding

Firstly, my English very bad. Sorry about that.

I have a foreign key in cards table like:

$table->foreignId('wallet_id')->constrained('wallets', 'id')->onDelete('cascade');

Since some reasons I need change cascade to set null on that column

I have try (in a new migration):

$table->dropForeign('cards_wallet_id_foreign');
$table->foreignId('wallet_id')
    ->nullable()
    ->onDelete('set null')
    ->change();

that run okey but when delete it not set null :((

How I can solve that. Thank you!!

CodePudding user response：

You can not just modify the existing migration, You need to make another one

<?php
  
use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;
  
class ChangeSomeTableColumn extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::table('the_table_you_are_changing', function (Blueprint $table) {
            $table
                ->foreignId('wallet_id')
                ->constrained('wallets', 'id')
                ->onDelete('set null')
                ->change();
        });
    }
    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
          
    }
}

CodePudding user response：

You must change your table migration schema in a new migration, and make sure you set the foreign key field as nullable:

$table->integer('wallet_id')->unsigned()->nullable();

and then use set null like this:

$table->...->onDelete('set null');