问题描述

数据库foreign key error 1215

 create table department(dept_name varchar(20) not null primary key building varchar(20)budget numeric(122)); create table instructor( ID varchar(5)  name varchar(20)  dept_name varchar(20)  salary numeric(121));create table course( course_id varchar(8)  title     varchar(50)  dept_name varchar(20) references department  credits   numeric(20)  primary key (course_id)  #foreign key constraints can be here too :    #foreign key (dept_name) references department);/*alter table course   change column course_id     course_id varchar(8) unique;*/create table section( course_id     varchar(8)  sec_id        varchar(8)  semster       varchar(6)  year          numeric(40)  building      varchar(15)  room_number   varchar(7)  time_sloth_id varchar(4)  primary key(course_idsemsteryear)  foreign key (course_id) references course);create table teach( ID          varchar(5)  course_id   varchar(8)  semster     varchar(6)  year        numeric(40)  primary key (IDcourse_idsemster year)  foreign key (ID) references instructor  foreign key (course_id semster year) references section);

这段代码运行在MySql上总是在create table section的时候报error 1215不能添加外键......求问为什么啊......

解决方案

试试foreign key (course_id) references course(course_id)？