php - 错误 : Cannot add or update a child row: a foreign key constraint fails?

Question

Error: Cannot add or update a child row: a foreign key constraint fails? (testlogin.leavetable, CONSTRAINT leavetable_ibfk_1 FOREIGN KEY
(users_id) REFERENCES users (id) ON DELETE CASCADE ON UPDATE CASCADE)

过去一天半以来一直收到此消息。试图在两个表之间建立一对多(外键)关系。在 users:id 和 leavetable:users_id 之间。当用户登录时，他们会得到一个 ID。当他们向 hours 列提交表单时，我希望 id 与表单数据保持一致。当有人创建新的 ID 号码并且它不会更新 leavetable:user_id 时，它会抛出错误。它抛出上面的错误。

这是我的代码:

CREATE TABLE IF NOT EXISTS `users` ( 
`email` varchar(255) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL, 
`id` int(11) NOT NULL, 
`password` char(64) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL, 
`salt` char(16) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL, 
`username` varchar(255) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL 
) ENGINE=InnoDB DEFAULT CHARSET=latin1; 



CREATE TABLE IF NOT EXISTS `leavetable` ( 
`hours` int(11) NOT NULL, 
`users_id` int(11) DEFAULT NOT NULL, 
`id` int(11) NOT NULL 
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1; 


 ALTER TABLE `users` 
 ADD PRIMARY KEY (`id`) USING BTREE, 
 ADD UNIQUE KEY `email` (`email`) USING BTREE, 
 ADD UNIQUE KEY `username` (`username`) USING BTREE; 

 ALTER TABLE `leavetable` 
 ADD PRIMARY KEY (`id`) USING BTREE, 
 ADD KEY `users_id` (`users_id`) USING BTREE; 

 ALTER TABLE `leavetable` 
 MODIFY `id` int(11) NOT NULL AUTO_INCREMENT; 
 -- AUTO_INCREMENT for table `users` 
 ALTER TABLE `users` 
 MODIFY `id` int(11) NOT NULL AUTO_INCREMENT; 

ALTER TABLE `leavetable` 
ADD CONSTRAINT `leavetable_ibfk_1` FOREIGN KEY (`users_id`) REFERENCES
`users` (`id`) ON DELETE CASCADE ON UPDATE CASCADE;

我的表结构:

+---------------------+
| Tables_in_testlogin |
+---------------------+
| leavetable          |
| users               |
+---------------------+

+----------+--------------+------+-----+---------+----------------+
| Field    | Type         | Null | Key | Default | Extra          |
+----------+--------------+------+-----+---------+----------------+
| email    | varchar(255) | NO   | UNI | NULL    |                |
| id       | int(11)      | NO   | PRI | NULL    | auto_increment |
| password | char(64)     | NO   |     | NULL    |                |
| salt     | char(16)     | NO   |     | NULL    |                |
| username | varchar(255) | NO   | UNI | NULL    |                |
+----------+--------------+------+-----+---------+----------------+
5 rows in set (0.01 sec)

+----------+---------+------+-----+---------+----------------+
| Field    | Type    | Null | Key | Default | Extra          |
+----------+---------+------+-----+---------+----------------+
| hours    | int(11) | NO   |     | NULL    |                |
| users_id | int(11) | NO   | MUL | NULL    |                |
| id       | int(11) | NO   | PRI | NULL    | auto_increment |
+----------+---------+------+-----+---------+----------------+
3 rows in set (0.01 sec)

Answer 1

首先你必须清理子表的数据然后清除mastertable之间的外键然后你可以清除任何数据