Answers for "how to remove null value key from request in laravel"

set null on foreign key deletion in laravel

$table->foreignId('forign_id')->nullable()->constrained("table_name")->cascadeOnUpdate()->nullOnDelete();

laravel on delete set null

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

#First make sure you set the foreign key field as nullable:
$table->integer('foreign_id')->unsigned()->nullable();