我的SQL多个类别-子类别-子类别 [英] my sql multiple category-subcategory-subcategory

问题描述

category subcategory subcategory
jewelry   body       nose ring,arm ring,ear ring 
          men        ring,ear ring

我有多个 category-> subcategory-> subcategory ，因此该表如何在MySQL中？

I have multiple category->subcategory->subcategory so how will be the table for this in MySQL?

推荐答案

像这样构造表：

Id   Category    ParentId
1     Jewelry     NULL
2     Body          1
3     nose ring     2
4     arm ring      2
5     ear ring      2
- 
-

这称为自引用表，即 ParentId 列包含 NULL 或同一表的 Id 列中的值。

This is called Self-Referencing Table i.e. ParentId columns contains either NULL or value from the Id column of same table.

所以只要您必须知道给定类别的所有直接子类别 ，您只需创建一个查询：

so whenever you have to know all the direct subcategories of a given category, you simply create a query like :

   Select * from CategoryMaster where ParentId = 2;

执行此操作，您将获得该子类别的所有子类别正文。

doing this you will get all the sub-categories for the sub-category Body.

现在，关于此数据结构最好的部分是，对于任何给定的子类，您都可以拥有n级子类-category和具有3列（最少）的同一张单表。

Now, the best part about this data-structure is that you can have n-levels of sub-categories for any given sub-category and same single table with 3 columns (at minimum) will do.

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