Question

假设我有作者（id，name），Book（id，name），Book_Author（bookid，authorid），Book_Reader表（bookId，authorId）表。

AUthor(id, name)
========

    1  | James
    2  | Ivan
    3  |John
    4  |Harry

Book(id, name)
=============

    1  |   Introducing Mysql
    2  |   Hibernate tutorials


Book_Author(bookId, authorId)
=========

    1  | 1
    2  | 3

Book_reader(bookId, authorId)
=============

        1  | 1
        1  | 3
        1  | 4

其中bookAuthor表代表书的作者，书籍读者代表作者阅读该书。

现在，我希望查询将返回我的书，书的作者和作者列表阅读该书。

Bookname             Author         Readers
================================================

    Introducing Mysql     James           James,John,Harry

或者我想要所有的作者是詹姆斯或读者的书是詹姆斯。谢谢，

Answer 1

select
b.name,
a1.name as author,
group_concat(a2.name) as reader
from 
book_reader br 
inner join book b on b.id = br.bookId
inner join book_Author ba on ba.bookId = br.bookId
inner join author a1 on a1.id = ba.authorId
inner join author a2 on a2.id = br.authorId
group by b.id

<强> DEMO

我想要詹姆斯是作家或詹姆斯是读者的所有书籍

对于上述情况，您可以使用where where condition

select
name,
type
from
(
  select
  b.name,
  'Author' as type
  from book b
  inner join book_author ba on ba.bookId = b.id
  inner join author a on a.id = ba.authorId
  where a.name = 'James'
  UNION ALL
  select
  b.name,
  'Reader' as Type
  from book b
  inner join book_reader br on br.bookId = b.id
  inner join author a on a.id = br.authorId
  where a.name = 'James'
)t

<强> DEMO

我添加了UNION ALL以列出所有内容并输入列作为通知阅读或作者的列。如果你不想那只是删除，也可以只使用UNION以防万一你不想要重复的书名。

Answer 2

书籍，作者和读者：

SELECT b.name AS BookName, a1.name AS AuthorName, group_concat(DISTINCT a2.name) AS readers
FROM book_reader AS br 
JOIN book AS b on b.id = br.book_id
JOIN book_author AS ba on ba.book_id = br.book_id
JOIN author AS a1 on a1.id = ba.author_id
JOIN author AS a2 on a2.id = br.author_id
GROUP BY b.id;

我在此查询中使用了表别名来减少输入的数量。 GROUP_CONCAT()函数用于将读者名称组合成一列。

作者是詹姆斯的书：

SELECT book.name
FROM book_author
JOIN book ON book.id = book_author.book_id
JOIN author ON author.id = book_author.author_id
WHERE author.name = "James";

读者是詹姆斯的书：

SELECT book.name
FROM book_reader
JOIN book ON book.id = book_reader.book_id
JOIN author ON author.id = book_reader.author_id
WHERE author.name = "James";

Sql查询将从两个或多个表返回列

2 个答案: