mysql - 修改表列外键？

Question

以https://dev.mysql.com/doc/refman/5.1/en/innodb-foreign-key-constraints.html#.T8foMxTft0x为例：

CREATE TABLE product (category INT NOT NULL, id INT NOT NULL,
                      price DECIMAL,
                      PRIMARY KEY(category, id)) ENGINE=INNODB;
CREATE TABLE customer (id INT NOT NULL,
                       PRIMARY KEY (id)) ENGINE=INNODB;
CREATE TABLE product_order (no INT NOT NULL AUTO_INCREMENT,
                            product_category INT NOT NULL,
                            product_id INT NOT NULL,
                            customer_id INT NOT NULL,
                            PRIMARY KEY(no),
                            INDEX (product_category, product_id),
                            FOREIGN KEY (product_category, product_id)
                              REFERENCES product(category, id)
                              ON UPDATE CASCADE ON DELETE RESTRICT,
                            INDEX (customer_id),
                            FOREIGN KEY (customer_id)
                              REFERENCES customer(id)) ENGINE=INNODB;

I have a similar problem, but I noticed you can't change Foreign key (customer ID in this example) to unsigned, set default, or length, etc. I can't change either table with alter table, apparently because they're dependent and have to be the same type. Is there any other way this may be done?

Answer 1

您可以删除外键，更改列，然后再次添加外键。