分层数据 - 嵌套集模型：MySql [英] Hierarchical Data - Nested Set Model: MySql

问题描述

我只是学习如何实现嵌套集合模型，但仍然与其涉及可能是多个类别的一部分的项目的某个方面混淆。在下面的示例中，从 此处 中提取，镜子很多其他例子我遇到了...

当您添加Apples时，如何避免在DB中出现重复，因为它们是多色的（即红色，黄色，绿色）？

<你不要避免重复，苹果（或苹果的引用）将在你的树中放置两次，否则它不会是一棵树，而是一棵树。图形。如果你构建一个... Swing JTree或一个HTML树，你的问题同样适用。）

嵌套集模型只是一种有效的方法推送和遍历树结构在关系DB中。它不是数据结构本身。它在MySQL用户中更受欢迎，因为MySQL缺少处理树结构的功能（例如像Oracle提供的那样）。

干杯！

I am just learning how to implement the Nested Set Model but still have confusion with a certain aspect of it involving items that may be part of multiple categories. Given the example below that was pulled from HERE and mirrors many other examples I have come across...

How do you avoid duplication in the DB when you add Apples since they are multi-colored (i.e. Red, Yellow, Green)?

解决方案

You do not avoid duplications and the apple (or a reference to the apple) will be placed twice in your tree otherwise it won't be a tree but rather a graph. Your question is equally applicable if you build a... Swing JTree or an HTML tree ;).

The nested set model is just an efficient way to push and traverse a tree structure in a relational DB.It is not a data structure itself. It's more popular among MySQL users since MySQL lacks functionality for processing tree structures (e.g. like the one that Oracle provides).

Cheers!

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