Rule 11:- For unlimited hierarchical data self-reference PK and FK

Many times we come across data with unlimited parent child hierarchy. For instance consider a Multi-level marketing scenario where one sales person can have multiple sales people below them. For such kind of scenarios using a self-referencing primary key and foreign key will help to achieve the same.

This article is not meant to say that do not follow normal forms , but do not follow them blindly , look at your project nature and type of data you are dealing with.

Out of full respect, below is a video which explains 3 normal forms step by step using a simple school table.
 

Rule 11：无限制结构数据，自引用PK和FK

我们会经常碰到一些无限父子分级结构的数据。例如：考虑到一个多层次的营销方案，其中一个销售人员可以领导多个销售人员。在这种情况下，你可以使用自定义的主键和设置外键来帮助你实现统一。

您可以根据自身的项目需求选择不同的数据处理方法。如下所示：三种常规范式。

英文出自：c-sharpcorner