问题描述
我有一个组件数据库.每个组件都属于特定类型.这意味着组件和类型之间存在多对一的关系.当我删除一个类型时，我想删除所有具有该类型外键的组件.但是如果我没记错的话，级联删除会在删除组件时删除类型.有什么办法可以做到我所描述的吗?
I have a database of components. Each component is of a specific type. That means there is a many-to-one relationship between a component and a type. When I delete a type, I would like to delete all the components which has a foreign key of that type. But if I'm not mistaken, cascade delete will delete the type when the component is deleted. Is there any way to do what I described?
推荐答案
这是您要包含在组件表中的内容.
Here's what you'd include in your components table.
CREATE TABLE `components` (
`id` int(10) unsigned NOT NULL auto_increment,
`typeId` int(10) unsigned NOT NULL,
`moreInfo` VARCHAR(32),
-- etc
PRIMARY KEY (`id`),
KEY `type` (`typeId`)
CONSTRAINT `myForeignKey` FOREIGN KEY (`typeId`)
REFERENCES `types` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
)
请记住，您需要使用 InnoDB 存储引擎:默认的 MyISAM 存储引擎不支持外键.
Just remember that you need to use the InnoDB storage engine: the default MyISAM storage engine doesn't support foreign keys.
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