mysql - 从多对多关系中获取数据

Question

我想从书表中获取标题，从主题表中获取某个作者的所有书籍的主题名称

这是表格关系

我试图从表格中选择标题和主题，但我无法让它与多对多关系一起使用

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

我想过做两个单独的查询，如果有人可以帮助我，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];

并且很好地发布模型:)

编辑以匹配确切需要：

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';

顺便说一句，您有一个，"Column 'author_ID' in where clause is ambiguous"因为此列同时出现在 Book_Author 和 Author 中。这就是为什么你必须在它前面加上表名:)