如何使用没有公共列的链接表连接表

Question

我们如何加入这些student_info和class_info表没有公共列，但两个外键都存储在class_student表中。

Answer 1

调整以适合您的WHERE子句，特定数据库和JOIN需求。

对于学生的课程：

SELECT * 
FROM student_info JOIN class_student ON student_info.student_id = class_student.student_id 
        JOIN class_info ON class_student.class_id = class_info.class_id 
WHERE student_info.student_id = ... 

对于一类的学生：

SELECT * 
FROM class_info JOIN class_student ON class_info.class_id  = class_student.class_id 
       JOIN student_info ON class_student.student_id = student_info.student_id 
WHERE class_info.class_id = ...