title: Key exists in table but shows Can't Drop foreign key in MySQL
body: <p>The result of "SHOW CREATE TABLE order_products" are</p>
  
  <pre><code>CREATE TABLE `order_products` (
   `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
   `quantity` int(11) NOT NULL,
   `price` double DEFAULT NULL,
   `amount` double(8,2) NOT NULL,
   `product_id` int(10) unsigned NOT NULL,
   `tax_id` int(10) unsigned DEFAULT NULL,
   `discount_id` int(10) unsigned DEFAULT NULL,
   `order_id` int(10) unsigned DEFAULT NULL,
   `username` varchar(191) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
   `shop_name` varchar(191) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
   `created_at` timestamp NULL DEFAULT NULL,
   `updated_at` timestamp NULL DEFAULT NULL,
   PRIMARY KEY (`id`),
   KEY `order_products_product_id_foreign` (`product_id`),
   KEY `order_products_tax_id_foreign` (`tax_id`),
   KEY `order_products_discount_id_foreign` (`discount_id`),
   KEY `order_products_order_id_foreign` (`order_id`)
  ) ENGINE=InnoDB AUTO_INCREMENT=40 DEFAULT CHARSET=utf8mb4 
  COLLATE=utf8mb4_unicode_ci
  </code></pre>
  
  <p>And i try to delete my key "order_products_product_id_foreign" by</p>
  
  <pre><code>ALTER TABLE order_products DROP FOREIGN KEY order_products_product_id_foreign
  </code></pre>
  
  <p>But it gives me error </p>
  
  <pre><code>#1091 - Can't DROP 'order_products_product_id_foreign'; check that column/key exists
  </code></pre>