Question

I am writing an application that helps book exchange between users. I am using PHP and MySQL, and I am pretty new to them both.

表2

用户:用户属性(用户_id、姓名、出生......等)。
书籍:具有图书属性(书目、名称、作者、出版商等)。
副本:是书籍的实际复制件(复印件、状况、评论等)。
用户_copy:描述哪些用户持有该拷贝,由用户信息数据库和复印件组成。
复印件:是复印件和书籍的链接,由复印件和图书信息数据库组成。

My question is: what is the easiest and most efficient statement for getting the book attributes and copy attributes for each copy that a user holds?

Answer 1

您需要加入你们感兴趣的所有表格:书本、复印本、用户版和书本。用户持有的所有复制件的回归特性的电子数据表可考虑:

SELECT   B.bookID
       , B.name
       , B.author
       , B.publisher
       , C.condition
       , C.comments
       -- you may get other fields that you are interested in here..
  FROM book B
       INNER JOIN copy_book CB ON B.bookID = CB.bookID
       INNER JOIN user_copy UC ON UC.copyID = CB.copyID
       INNER JOIN copy C ON C.copyID = UC.copyID
  WHERE UC.userID = <the user Id that you want>

我希望,我非常清楚地说明发言的内容,但如果有问题,请问。

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