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Editor to share with you how to write the foreign keys of mysql, I believe most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

How to write the foreign key of mysql?

Mysql add Foreign key:

Add a foreign key to the data table that has been added:

Syntax:

Alter table table name add constraint FK_ID foreign key (your foreign key field name) REFERENCES table name (primary key field name of the corresponding table)

Example:

Alter table tb_active add constraint FK_ID foreign key (user_id) REFERENCES tb_user (id) / / FK_ID is the name of the foreign key / * CREATE TABLE `tb_ active` (`id`int (11) NOT NULL AUTO_INCREMENT, `title`varchar (100) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL, `content` text CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL, `user_ id` int (11) NOT NULL,PRIMARY KEY (`id`), KEY `user_ id` (`user_ id`), KEY `user_id_ 2` (`user_ id`) CONSTRAINT `user_ ID` FOREIGN KEY (`tb_ id`) REFERENCES `tb_ user` (`id`) ENGINE=InnoDB DEFAULT CHARSET=latin1*/ is all the content of how to write the foreign key of mysql Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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