Error: Cannot add or update a child row: a foreign key constraint fails? (
testlogin
.leavetable
, CONSTRAINTleavetable_ibfk_1
FOREIGN KEY
(users_id
) REFERENCESusers
(id
) ON DELETE CASCADE ON UPDATE CASCADE)
过去一天半以来一直收到此消息。尝试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,他们会获得一个 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 号并且不会更新 leavetable:user_id
时,它会抛出错误。它会抛出上面的错误。
发生什么事了?我以正确的方式处理这个问题吗?
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)
PHP 代码:
mysql_select_db("testlogin", $con);
$sql="INSERT INTO leavetable (hours)
VALUES
('$_POST[hours]')";
if (!mysql_query($sql,$con))
{
die('Error: ' . mysql_error());
}
最佳答案
$sql="INSERT INTO leavetable (hours)
VALUES
('$_POST[hours]')";
上面的sql代码不包含任何对用户id的引用。 mysql应该如何猜测这个休假条目属于哪个用户?在插入语句的列和值部分中包含 tge 用户 ID。也许您应该将用户 ID 存储在 php session 中。
关于mysql - SQL一对多用户外键问题,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/33107851/