mysql - 从多对多关系中获取数据

Question

我想从书表中获取某个作者所有书籍的标题和主题表中的主题名称

这是表的关系

我试图从表格中选择标题和主题，但我无法让它处理多对多关系

SELECT book_title,subject_name FROM book,subject WHERE $subject_ID = subject_ID INNER JOIN book_author ON author_ID = '$author_ID'

我想提出两个单独的问题，如果有人能帮助我，我会很高兴。

Answer 1

试试这个:

SELECT book_title, subject_name
FROM Book
INNER JOIN Book_Author ON Book.book_ISBN = Book_Author.book_ISBN
INNER JOIN Author ON Book_Author.author_ID = Author.author_ID
INNER JOIN Subject ON Subject.subject_ID = Book.subject_ID
WHERE author_lastname = [whatever];

发布模型的工作做得很好 :)

根据具体需要进行编辑:

SELECT book_title, subject_name
FROM Book
INNER JOIN Book_Author ON Book.book_ISBN = Book_Author.book_ISBN
INNER JOIN Subject ON Subject.subject_ID = Book.subject_ID
WHERE author_ID = '11';

顺便说一下，您有一个 “Column 'author_ID' in where clause is ambiguous” 因为该列同时出现在 Book_Author 和 Author 中。这就是为什么你必须在它前面加上表名:)