mysql - Mysql用一个引用多列

Question

如何使 3 列具有字段引用？下面的代码不正确。

CREATE TABLE `example` (

`id` bigint(20) NOT NULL AUTO_INCREMENT,
`userid_do1` int(11) DEFAULT NULL,
`userid_do2` int(11) DEFAULT NULL,
`userid_do3` int(11) DEFAULT NULL,
 PRIMARY KEY (`id`),
 CONSTRAINT `example_ibfk_1` FOREIGN KEY (`userid_do1,userid_do2,userid_do3`) REFERENCES `usertable` (`id`),
) ENGINE=InnoDB

Answer 1

您需要为引用另一个表的列的每一列创建一个约束。

CONSTRAINT example_ibfk_1 FOREIGN KEY (userid_do1) REFERENCES usertable(id),
CONSTRAINT example_ibfk_2 FOREIGN KEY (userid_do2) REFERENCES usertable(id),
CONSTRAINT example_ibfk_3 FOREIGN KEY (userid_do3) REFERENCES usertable(id)