mysql - 使用外键创建表时出错

Question

我第一次建模了一个非常简单的数据库并尝试插入查询:

CREATE TABLE `product` (
`pid` varchar(255) NOT NULL,
`mfr` varchar(255) NULL,
`pnum` varchar(255) NOT NULL,
`ssku` varchar(255) NULL,
PRIMARY KEY (`pid`)
);

CREATE TABLE `detail` (
`pid` varchar(255) NOT NULL,
`sdesc` varchar(255) NULL,
`supplier` varchar(255) NULL,
PRIMARY KEY (`pid`)
);


CREATE TABLE `images` (
`pid` varchar(255) NOT NULL,
`url` varchar(255) NULL,
`alt` varchar(255) NULL,
`position` varchar(255) NULL,
PRIMARY KEY (`pid`)
);

ALTER TABLE `detail` ADD CONSTRAINT `fk_detail` FOREIGN KEY (`pid`) REFERENCES `product` ();
ALTER TABLE `images` ADD CONSTRAINT `pid` FOREIGN KEY () REFERENCES `product` ();

...但我收到此错误:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ') REFERENCES `product` ()' at line 1

我做错了什么？

Answer 1

您必须将列名传递给 REFERENCES 子句:

REFERENCES product(pid);

此外，您要在 images 约束上创建一个空白外键:

FOREIGN KEY () REFERENCES `product` ();