如何在 mysql 中使用删除级联?

How do I use on delete cascade in mysql?(如何在 mysql 中使用删除级联?)

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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