MySQL:ERROR 1022(23000):无法写入; 表'#sql-2b8_2'中的重复键

Question

我要实现一个书店数据库.我创建了表book,author和publisher.我想做出以下两种关系.

Book is written by Author.
Book is published by Publisher.

为了实现这些关系,我写了一些SQL语句,如:

create table book(
            ISBN varchar(30) NOT NULL,
            title varchar(30) not null,
            author varchar(30) not null,
            stock Int,
            price Int,
            category varchar(30), 
            PRIMARY KEY ( ISBN )
);

create table author(
            author_id int not null auto_increment,
            author_name varchar(15) NOT NULL,
            address varchar(50) not null,
            ISBN varchar(30) not null,
            primary key (author_id)
);

alter table author add constraint ISBN foreign key (ISBN) references book (ISBN);

create table publisher(
            publisher_id int not null auto_increment,
            publisher_name varchar(15) NOT NULL,
            address varchar(50) not null,
            ISBN varchar(30) not null,
            primary key (publisher_id)
);

alter table publisher add constraint ISBN foreign key (ISBN) references book (ISBN);

当MySQL shell执行最后一个alter语句时,我收到此错误.

ERROR 1022 (23000): Can't write; duplicate key in table '#sql-2b8_2'

原来,外键不能指定两次？怎么了？先感谢您.

Answer 1

您得到的duplicate key error原因是ISBN,根据您alter对author表的第一个语句,数据库中已存在一个名为present 的约束

alter table author add constraint ISBN foreign key (ISBN) references book (ISBN);

尝试在Publisher表中使用不同的名称作为约束

alter table publisher add constraint ISBN1 
foreign key (ISBN) references book (ISBN);