无法添加或更新子行：mysql phpmyadmin中的外键约束失败

Question

我的数据库名为bookedscheduler，当我导入sql文件时，会发生这样的错误。

Cannot add or update a child row: a foreign key constraint fails (`bookedscheduler`.`group_roles`, CONSTRAINT `group_roles_ibfk_2` FOREIGN KEY (`role_id`) REFERENCES `roles` (`role_id`) ON DELETE CASCADE ON UPDATE CASCADE) 

这是表'角色'部分的代码：

DROP TABLE IF EXISTS `roles`;
CREATE TABLE `roles` (
 `role_id` tinyint(2) unsigned NOT NULL,
 `name` varchar(85),
 `role_level` tinyint(2) unsigned,
 PRIMARY KEY (`role_id`)
) ENGINE=InnoDB DEFAULT CHARACTER SET utf8;

以下是表'user_roles'的代码：

DROP TABLE IF EXISTS `group_roles`;
CREATE TABLE `group_roles` (
 `group_id` smallint(8) unsigned NOT NULL,
 `role_id` tinyint(2) unsigned NOT NULL,
 PRIMARY KEY (`group_id`, `role_id`),
 INDEX (`group_id`),
 FOREIGN KEY (`group_id`)
    REFERENCES groups(`group_id`)
    ON UPDATE CASCADE ON DELETE CASCADE,
 INDEX (`role_id`),
 FOREIGN KEY (`role_id`)
    REFERENCES roles(`role_id`)
    ON UPDATE CASCADE ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARACTER SET utf8;