[英]What is wrong with my mysql foreign key constraints?
我正在做一个个人项目,这是我一生中第一次真正地尝试建立一个经过规范化的数据库(至少在您进行规范化的第一个级别上)。 这是我的问题涉及的表:
CREATE TABLE `reoccurrences` (
`name` varchar(15) NOT NULL DEFAULT '',
`username` varchar(31) NOT NULL DEFAULT '',
`amount` float(7,2) NOT NULL DEFAULT '0.00',
`action` varchar(15) NOT NULL DEFAULT '',
`frequency` varchar(15) NOT NULL DEFAULT '',
PRIMARY KEY (`name`,`username`),
KEY `fk_reoccurrences_user` (`username`),
KEY `fk_reoccurrences_action` (`action`),
KEY `fk_reoccurrences_frequency` (`frequency`),
CONSTRAINT `fk_reoccurrences_action` FOREIGN KEY (`action`) REFERENCES `actions` (`name`),
CONSTRAINT `fk_reoccurrences_frequency` FOREIGN KEY (`frequency`) REFERENCES `frequencies` (`name`),
CONSTRAINT `fk_reoccurrences_user` FOREIGN KEY (`username`) REFERENCES `users` (`name`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
CREATE TABLE `days` (
`reoccurrence` varchar(15) NOT NULL,
`username` varchar(31) NOT NULL DEFAULT '',
`day` tinyint(2) NOT NULL,
PRIMARY KEY (`reoccurrence`,`username`,`day`),
KEY `fk_days_reoccurrence2` (`username`),
CONSTRAINT `fk_days_reoccurrence` FOREIGN KEY (`reoccurrence`) REFERENCES `reoccurrences` (`name`),
CONSTRAINT `fk_days_reoccurrence2` FOREIGN KEY (`username`) REFERENCES `reoccurrences` (`username`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
注意,主要问题(我相信)是在这两个表之间。 还有其他几个相关的表格,但是如果我开始列出它们,那么这篇文章会变得很长。 如果您想查看完整的数据结构,可以在github上查看我的项目: https : //github.com/dallascaley/finance (我为我的github自述文件中的常识性/缺乏常识表示歉意,这不是供公众观看)
当我开始向这些表添加数据时,就会发生问题。 这是我的数据:
reoccurrences:
name, username, amount, action, frequency
Pay , dallas , 2500 , credit, bi-weekly
Rent, dallas , 1400 , debit , monthly
days:
reoccurrence, username, day
Rent , dallas , 1
忽略我没有一天或几天没有列出工资的事实。 由于某种原因,当表处于这种状态时,我无法从重现表中删除“付款”记录。 当我运行这个:
DELETE FROM reoccurrences WHERE `name` = 'Pay' AND `username` = 'dallas';
我收到以下错误:
Cannot delete or update a parent row: a foreign key constraint fails (`test`.`days`, CONSTRAINT `fk_days_reoccurrence2` FOREIGN KEY (`username`) REFERENCES `reoccurrences` (`username`))
如何更改表格结构以解决此问题?
您可能只需要在工作days
解决约束,即可使用reoccurrences
的组合键:
CREATE TABLE `days` (
`reoccurrence` varchar(15) NOT NULL,
`username` varchar(31) NOT NULL DEFAULT '',
`day` tinyint(2) NOT NULL,
PRIMARY KEY (`reoccurrence`,`username`,`day`),
CONSTRAINT `fk_days_reoccurrence` FOREIGN KEY (`reoccurrence`,`username`) REFERENCES `reoccurrences` (`name`,`username`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
如您所见,我将fk_days_reoccurrence
更改为一个组合键,并完全删除了fk_days_reoccurrence2
(键和外键引用)。
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