向表中添加外键

Question

我需要做以下事情：

Select course_id 和 userid_DI 作为两个不同的外键 table course_users.

table users 有如下： userid_DI, Country, LoE_DI, YoB, Age, gender

table course 有如下： course_id, institution, course_number, course_term, Course_Short_Title, Course_Long_title

table course_users 有以下： course_id, userid_DI, registered, viewed, explored, grade

Answer 1

使用ALTER TABLE:

ALTER TABLE course_users 
    ADD FOREIGN KEY (course_id) REFERENCES course (course_id),
    ADD FOREIGN KEY (userid_DI) REFERENCES users (userid_DI);

向表中添加外键

adding foreign key to tables

mysql

mysql-workbench