具有多个父级的多对多层次结构-PHP，MySQL [英] Many-to-Many Hierarchy with Multiple Parents - PHP, MySQL

问题描述

我正在尝试按类别创建技术书籍列表，其中每本书籍可以属于多个类别，并且每个类别既可以是父类别又可以是子类别.

I'm trying to create a list of technology books by category, where each book can belong to more than one category, and each category can be both a parent category and a sub-category.

这是一个例子:

JavaScript
JavaScript模式
面向对象的JavaScript

JavaScript
JavaScript Patterns
Object-Oriented JavaScript

• Ajax
  Ajax权威指南
  防弹Ajax

• Ajax
  Ajax Definitive Guide
  Bulletproof Ajax

jQuery
学习jQuery 1.3
PHP jQuery食谱

jQuery
Learning jQuery 1.3
PHP jQuery Cookbook

PHP
简而言之，PHP
PHP jQuery食谱

PHP
PHP in a Nutshell
PHP jQuery Cookbook

Ajax
Ajax权威指南
防弹Ajax

Ajax
Ajax Definitive Guide
Bulletproof Ajax

• XML
  XML黑客
  非废话XML

• XML
  XML Hacks
  No-Nonsense XML

-

如您所见...

• "PHP jQuery Cookbook"这本书分为两类:PHP和jQuery
• "Ajax"类别既是JavaScript的子级，又是XML的父级(但XML并非JavaScript的子级)

我是这样设计数据库表的:

I've designed the database tables this way:

BOOK:          book_id, book_title  
CATEGORY:      category_id, category_name  
BOOK_CATEGORY: book_id, category_id
CATEGORY_TREE: parent_category_id, child_category_id

我已经阅读了许多其他有关MySQL层次结构数据的问题/答案，但是没有什么可以处理这种松散"层次结构.

I've read many other questions/answers on hierarchical data in MySQL, but nothing that can handle this type of "loose" hierarchy.

有人知道如何以这种方式建立列表吗?

Does anyone know how to set up a list in this way?

推荐答案

假设您的类别无法形成周期，例如a-> b-> c-> a，则您的结构称为有向无环图，这不易处理在SQL中，但可能.谷歌搜索应该会产生一些结果，您也可以从这里开始: http://www.codeproject.com/KB/database/Modeling_DAGs_on_SQL_DBs.aspx

Assuming your categories cannot form cycles, like a->b->c->a, your structure is called directed acyclic graph, which is not easy to handle in SQL, but possible. Googling that should give some results, you can also start here: http://www.codeproject.com/KB/database/Modeling_DAGs_on_SQL_DBs.aspx

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