多个SQL联接

我需要执行一个查询来从多个表中检索数据，但我对如何一次完成这一切感到相当困惑

Books: _ISBN , BookTitle, Edition, Year, PublisherID, Pages, Rating
Categories: _CategoryID, Category
Categories_Books: _Categories_Category_ID, _Books_ISBN
Publishers: _Publisherid, Publisher
Writers: _WriterID, LastName
Writers_Books: _Writers_WriterID, _Books_ISBN

Categories\u Books

和

Writers\u Books

是帮助我实现表之间多对多关系的中间表

我需要一个包含多个联接的查询来选择：

• 书名、版本、年份、页数、书籍评级
• 类别中的类别
• 从出版商到出版商
• 作者的姓氏

---

它将是这样的：

SELECT b.Title, b.Edition, b.Year, b.Pages, b.Rating, c.Category, p.Publisher, w.LastName
FROM
    Books b
    JOIN Categories_Book cb ON cb._ISBN = b._Books_ISBN
    JOIN Category c ON c._CategoryID = cb._Categories_Category_ID
    JOIN Publishers p ON p._PublisherID = b.PublisherID
    JOIN Writers_Books wb ON wb._Books_ISBN = b._ISBN
    JOIN Writer w ON w._WritersID = wb._Writers_WriterID

Book: ID, ISBN , BookTitle, Edition, Year, PublisherID, Pages, Rating
Category: ID, [Name]
BookCategory: ID, CategoryID, BookID
Publisher: ID, [Name]
Writer: ID, LastName
BookWriter: ID, WriterID, BookID

您可以使用

join

语句来指示表A中哪些字段映射到表B。我在这里使用别名，这就是您看到

Books B

的原因

Books

表在查询的其余部分将被称为

B

。这样可以减少打字
仅供参考，您的命名约定非常奇怪，我希望它更像这样：

SELECT b.Title, b.Edition, b.Year, b.Pages, b.Rating, c.Category, p.Publisher, w.LastName
FROM
    Books b
    JOIN Categories_Book cb ON cb._ISBN = b._Books_ISBN
    JOIN Category c ON c._CategoryID = cb._Categories_Category_ID
    JOIN Publishers p ON p._PublisherID = b.PublisherID
    JOIN Writers_Books wb ON wb._Books_ISBN = b._ISBN
    JOIN Writer w ON w._WritersID = wb._Writers_WriterID

Book: ID, ISBN , BookTitle, Edition, Year, PublisherID, Pages, Rating
Category: ID, [Name]
BookCategory: ID, CategoryID, BookID
Publisher: ID, [Name]
Writer: ID, LastName
BookWriter: ID, WriterID, BookID

---

您可以使用以下内容：

SELECT
    Books.BookTitle,
    Books.Edition,
    Books.Year,
    Books.Pages,
    Books.Rating,
    Categories.Category,
    Publishers.Publisher,
    Writers.LastName
FROM Books
INNER JOIN Categories_Books ON Categories_Books._Books_ISBN = Books._ISBN
INNER JOIN Categories ON Categories._CategoryID = Categories_Books._Categories_Category_ID
INNER JOIN Publishers ON Publishers._Publisherid = Books.PublisherID
INNER JOIN Writers_Books ON Writers_Books._Books_ISBN = Books._ISBN
INNER JOIN Writers ON Writers.Writers_Books = _Writers_WriterID.

---

听起来不错，让我们去掉网站的一个主要区别。去meta.stackoverflow.com上发布，看看他们怎么说。我相信每个人都会同意你的观点。@Kris这可能是家庭作业，但sql查询非常简单，所以在我看来，最好的学习方法是阅读查询，一切都是直截了当的，这样他就可以学习正确的语法。我为这样的回答感到高兴，当我搜索“sql多重连接”时，他们会出现在谷歌上并作为所有未来用户的参考。

internal

是可选的

JOIN

只会给出相同的结果。是的，我知道我的命名约定在这方面非常奇怪。回顾我正在执行的连接，首先让我感到困惑。谢谢你的帮助。