停止重复mysql中的列值

Question

我有两个通过id相关的表。

书：

book_id | book_name | year | publisher | slug

章：

chapter_id | book_id | chapter_name

现在，当我查询数据库以找到与这样一本书相关的所有章节时：

SELECT book_name, chapter_name FROM ci_books, ci_chapters WHERE ci_books.book_id = ci_chapters.book_id AND slug = 'twelvers-dawn';

我明白了：

**book_name | chapter_name**
twelvers  | Rising Sun
twelvers  | Slow Down
twelvers  | Masochist

我得到了每一章重复的书的名称，我怎样才能阻止名称重复，以便只显示一次名称并显示所有章节？

Answer 1

您可以使用GROUP_CONCAT()之类的：

SELECT book_name, GROUP_CONCAT(chapter_name) as ChapterNames 
FROM ci_books, ci_chapters 
WHERE ci_books.book_id = ci_chapters.book_id AND slug = 'twelvers-dawn'
GROUP BY book_name;

请参阅资源here

Answer 2

将GROUP_CONCAT()与GROUP_BY

一起使用

SELECT book_name, GROUP_CONCAT(chapter_name) AS chapter_names
FROM ci_books, ci_chapters 
WHERE ci_books.book_id = ci_chapters.book_id AND slug = 'twelvers-dawn'
GROUP BY book_name;