了解网络数据库模型

Understanding the Network Database Model

了解网络数据库模型

The network database model was a progression from the hierarchical database model and was designed to solve some of that model's problems, specifically the lack of flexibility. Instead of only allowing each child to have one parent, this model allows each child to have multiple parents (it calls the children members and the parents owners). It addresses the need to model more complex relationships such as the orders/parts many-to-many relationship mentioned in the hierarchical article. As you can see in the figure below, A1 has two members, B1 and B2. B1. is the owner of C1, C2, C3 and C4. However, in this model, C4 has two owners, B1 and B2.

网络数据库模型是从分层数据库模型发展而来的，旨在解决该模型的某些问题，特别是缺乏灵活性。该模型不仅允许每个孩子有一个父母，而且还允许每个孩子有多个父母（它称为孩子成员和父母所有者）。它满足了对建模更复杂关系的需求，例如层次结构文章中提到的订单/零件多对多关系。如下图所示，A1有两个成员B1和B2。B1。是C1，C2的所有者，C3和C4。但是，在此模型中，C4具有两个所有者B1和B2。

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Of course, this model has its problems, or everyone would still be using it. It is more difficult to implement and maintain, and, although more flexible than the hierarchical model, it still has flexibility problems, Not all relations can be satisfied by assigning another owner, and the programmer still has to understand the data structure well in order to make the model efficient.

当然，此模型有其问题，否则每个人都仍会使用它。实施和维护更困难，并且尽管比分层模型更灵活，但仍然存在灵活性问题。并非所有关系都可以通过分配另一个所有者来满足，程序员仍然必须很好地理解数据结构才能做到。使模型高效。