我如何使用删除级联在MySQL？ [英] How do I use on delete cascade in mysql?

问题描述

我有一个组件数据库。每个组件都是特定的类型。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，我想删除所有具有该类型的外键的组件。但是，如果我没有弄错，级联删除将删除该组件时的类型。有什么办法可以做我所描述的吗？

解决方案

以下是组件表中的内容。

$ b $ $ $ $ $ $ $ $ $ $ $ $ $'$ $'$ $ $'$'$'$' （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。 b

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?

解决方案

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
)

Just remember that you need to use the InnoDB storage engine: the default MyISAM storage engine doesn't support foreign keys.

这篇关于我如何使用删除级联在MySQL？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！