Question

我收到一条错误消息：Error Code: 1217. Cannot delete or update a parent row: a foreign key constraint fails

不确定我为什么会收到此错误。任何线索？

以下代码：

-- DROP EXISTING TABLES --

DROP TABLE IF EXISTS `category`;
DROP TABLE IF EXISTS `format`;
DROP TABLE IF EXISTS `customer`;
DROP TABLE IF EXISTS `rentals`;
DROP TABLE IF EXISTS `videos`;

-- CREATE CATEGORY TABLE --
CREATE TABLE `category` (
    `category_id` int(10) NOT NULL,
    PRIMARY KEY (`category_id`)
) ENGINE = InnoDB DEFAULT CHARSET = utf8;

-- CREATE FORMAT TABLE --
CREATE TABLE `format` (
    `format_id` int(10) NOT NULL,
    PRIMARY KEY (`format_id`)
) ENGINE = InnoDB DEFAULT CHARSET = utf8;

-- CRTEATE VIDEOS TABLE --
CREATE TABLE `videos` (
    `video_id` int(10) NOT NULL,
    `title` varchar(50) NOT NULL,
    `format_id` int(10) NOT NULL,
    `cost` double NOT NULL,
    `category_id` int(10) NOT NULL,
    PRIMARY KEY (`video_id`),
    CONSTRAINT `fk_video_format` FOREIGN KEY (`format_id`) REFERENCES `format` (`format_id`),
    CONSTRAINT `fk_video_category` FOREIGN KEY (`category_id`) REFERENCES `category` (`category_id`)
) ENGINE = InnoDB DEFAULT CHARSET = utf8;

-- CREATE CUSTOMER TABLE --
CREATE TABLE `customer` (
    `customer_id` int(10) NOT NULL,
    `last_name` varchar(50) NOT NULL,
    `first_name` varchar(50) NOT NULL,
    `address` varchar(100) NOT NULL,
    `city` varchar(50) NOT NULL,
    `state` varchar(10) NOT NULL,
    `zip` int(10) NOT NULL,
    PRIMARY KEY (`customer_id`)
) ENGINE = InnoDB DEFAULT CHARSET = utf8;

-- CREATE RENTALS TABLE --
CREATE TABLE `rentals` (
    `rental_id` int(10) NOT NULL,
    `date_out` datetime NOT NULL,
    `date_due` datetime NOT NULL,
    `date_in` datetime NOT NULL,
    `delivery_status` varchar(50),
    `cost` double NOT NULL,
    `late_fee` double NOT NULL,
    `customer_id` int(10) NOT NULL,
    `video_id` int(10) NOT NULL,
    PRIMARY KEY (`rental_id`),
    CONSTRAINT `fk_video_customer` FOREIGN KEY (`customer_id`) REFERENCES  `customer` (`customer_id`),
    CONSTRAINT `fk_video_cost` FOREIGN KEY (`cost`) REFERENCES `videos` (`cost`),
    CONSTRAINT `fk_video_id` FOREIGN KEY (`video_id`) REFERENCES `videos` (`video_id`)
) ENGINE = InnoDB DEFAULT CHARSET = utf8;

我相信一切都与关键和外键关键。格式化看起来也是正确的。除非我在这里做了一些完全错误的事情。

Answer 1

忽略上面评论中描述的cost问题，1217错误很常见，因为当您放弃时，您必须按照创建的保留顺序执行此操作才能安全地执行此操作。

假设您已成功连续创建表A，B，C，D，您需要按照D，C，B，A的顺序删除它们。

这只是因为如果孩子有FK有效，就不能删除父母。通过首先放弃孩子，错误不会浮出水面。

外键约束失败（MySQL）

1 个答案: