如何在 mysql 中使用删除级联？
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How do I use on delete cascade in mysql?
提问by Marius
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?
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？
回答by nickf
Here's what you'd include in your components table.
这是您要包含在组件表中的内容。
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.
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。
回答by Silambarasan
You have to define your Foreign Key constraints as ON DELETE CASCADE.
您必须将外键约束定义为 ON DELETE CASCADE。
Note:You need to use InnoDB storage engine, the default MyISAM storage engine not support foreign keys relation.
注意：需要使用 InnoDB 存储引擎，默认 MyISAM 存储引擎不支持外键关系。
CREATE TABLE `table2` (
`id` int(11) NOT NULL auto_increment,
`name` int(11) NOT NULL,
PRIMARY KEY (`id`),
KEY `ids` (`ids`)
CONSTRAINT `foreign` FOREIGN KEY (`ids`)
REFERENCES `table2` (`ids`) ON DELETE CASCADE ON UPDATE CASCADE
)
回答by md asif rahman
use this sql
使用这个 sql
DELETE T1, T2 FROM T1 INNER JOIN T2 ON T1.key = T2.key WHERE condition
DELETE T1, T2 FROM T1 INNER JOIN T2 ON T1.key = T2.key WHERE 条件
