mysql外键概念 [英] mysql foreign key concept

问题描述

CREATE TABLE parent (id INT NOT NULL,
                     PRIMARY KEY (id)
) ENGINE=INNODB;


CREATE TABLE child (id INT, parent_id INT,
                    INDEX par_ind (parent_id),
                    FOREIGN KEY (parent_id) REFERENCES parent(id)
                      ON DELETE CASCADE
) ENGINE=INNODB;

我不明白将ENGINE = INNODB放在这里的含义，为什么我们使用ON DELETE CASCADE?

I dont understand the meaning of putting ENGINE = INNODB here, and why do we use ON DELETE CASCADE?

推荐答案

engine = innodb将确保您获得外键支持.默认的MyISAM引擎不支持外键.如果删除了父表中的引用行，则在删除时级联将删除子行.

engine=innodb will ensure you get foreign key support. The default MyISAM engine doesn't support foreign keys. On delete cascade will remove the child row if the referenced row in the parent table is removed.

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