Understanding the Network Database Model
了解網(wǎng)絡(luò)數(shù)據(jù)庫(kù)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.
網(wǎng)絡(luò)數(shù)據(jù)庫(kù)模型是從分層數(shù)據(jù)庫(kù)模型發(fā)展而來(lái)的，旨在解決該模型的某些問(wèn)題，特別是缺乏靈活性。該模型不僅允許每個(gè)孩子有一個(gè)父母，而且還允許每個(gè)孩子有多個(gè)父母（它稱為孩子成員和父母所有者）。它滿足了對(duì)建模更復(fù)雜關(guān)系的需求，例如層次結(jié)構(gòu)文章中提到的訂單/零件多對(duì)多關(guān)系。如下圖所示，A1有兩個(gè)成員B1和B2。B1。是C1，C2的所有者，C3和C4。但是，在此模型中，C4具有兩個(gè)所有者B1和B2。
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.
當(dāng)然，此模型有其問(wèn)題，否則每個(gè)人都仍會(huì)使用它。實(shí)施和維護(hù)更困難，并且盡管比分層模型更靈活，但仍然存在靈活性問(wèn)題。并非所有關(guān)系都可以通過(guò)分配另一個(gè)所有者來(lái)滿足，程序員仍然必須很好地理解數(shù)據(jù)結(jié)構(gòu)才能做到。使模型高效。
