mysql 查询多个值

Question

我有一个数据库，其中有一个学生表。结构是这样的

id      name
---     -----
1       Tini
2       Eka

然后是书籍表

id      title
---     ------
1       Cinderella's story
2       Pinochio
3       Mickey Mouse

然后借用

id      students_id     books_id
---     ------------    ---------
1       1               1,3
2       2               2,3

我如何得到“蒂尼正在借用灰姑娘的故事和米老鼠”？ 我已经尝试过这样的查询

select students.*, books.* , borrowing.*
    (select books.title from borrowing
     join books on books.id = borrowing.books_id
     where books_.id = borrowing.books_id limit 1)  as books_title
from borrowing
join students on students.id = borrowing.students_id
join books on books.id = borrowing.books_id 
GROUP BY books.title

但是它给了我一个错误

Answer 1

与其修复查询，不如规范化关系表借用的数据。

更改保存数据的方式，例如:

id      students_id     books_id
---     ------------    ---------
1       1               1
2       1               3
3       2               2
4       2               3

并且 id 列也不是必需的，您可以省略它。

然后获取每个学生的借阅列表就很简单了:

SELECT t1.name, GROUP_CONCAT(t3.title) AS borrowed_books
FROM students t1
LEFT JOIN borrowing t2 ON t2.students_id = t1.id
LEFT JOIN books t3 ON t3.id = t2.books_id
GROUP BY t1.name