MySQL Drop外键只有存在时才删除

$ mysql -u username -p

mysql> use database_name;

mysql> SHOW CREATE TABLE table_name;

CREATE TABLE `table_name` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `visitor_id` int(11) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `visitor_id` (`visitor_id`),
  CONSTRAINT `table_name_ibfk_1` FOREIGN KEY (`visitor_id`) REFERENCES `visitors` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci

mysql> ALTER TABLE table_name DROP FOREIGN KEY table_name_ibfk_1;

ERROR 1091 (42000): Can't DROP 'table_name_ibfk_2'; check that column/key exists