dbms支持哪幾種數據模型

資料模型 (Data Model)

A data model is a model that defines in which format the data are represented and accessed. Data model mainly defines some of the data elements and relationships that exist between them.

數據模型是定義數據以哪種格式表示和訪問的模型。 數據模型主要定義一些數據元素以及它們之間存在的關系。

數據模型的類型 (Types of Data Model)

There are basically two types of data model:

基本上有兩種類型的數據模型：

Record based data model

基于記錄的數據模型

Object based data model

基于對象的數據模型

1)基于記錄的數據模型 (1) Record based data model)

When the database is organized in some fixed format of records of several than the model is called record-based data model.

當數據庫以某種固定的格式組織記錄時，記錄模型比基于模型的記錄模型稱為基于記錄的數據模型。

A fixed number of fields, or attributes in each record type and each field is usually of a fixed length. The three most popular record-based data models are,

固定數量的字段或每種記錄類型和每個字段中的屬性通常具有固定的長度。 三種最流行的基于記錄的數據模型是：

(i) Relational data model

(i)關系數據模型

The relational data model uses tables to represent the data and the relationships among these data. Each table has multiple columns and each column is identified by a unique name. It is a low-level model.

關系數據模型使用表來表示數據以及這些數據之間的關系。 每個表都有多個列，并且每個列都由唯一的名稱標識。 這是一個低級模型。

Advantages of relational data model

關系數據模型的優點

• It is the simplest model at the conceptual level.

  它是概念上最簡單的模型。

• The relational data model makes it easy to design, implement, maintain, uses the database.

  關系數據模型使設計，實現，維護，使用數據庫變得容易。

• It does not affect the DBMS’s capability to access the data.

  它不影響DBMS訪問數據的能力。

• The main reason for the popularity of relational model is the presence of powerful query capability.

  關系模型流行的主要原因是強大的查詢功能。

(ii) Network data model

(ii)網絡數據模型

In the network data model, data model data are represented by collections of records. Relationships among data are represented by links. In this data model, graph data structure is used. It permits a record to have more than one parent.

在網絡數據模型中，數據模型數據由記錄的集合表示。 數據之間的關系由鏈接表示。 在此數據模型中，使用圖形數據結構。 它允許一個記錄有多個父級。

Advantages of Network data model

網絡數據模型的優勢

• The Network data model is also conceptually simple and easy to design.

  網絡數據模型在概念上也很容易設計。

• In the network data model relationships like one-to-one and many-to-many are exist.

  在網絡數據模型中，存在一對一和多對多的關系。

• In the network data model without the owner, no member exists.

  在沒有所有者的網絡數據模型中，不存在成員。

• In the network database terminology, a relationship is a set. Each set comprises two types of record an owner record and a member record.

  在網絡數據庫術語中，關系是一個集合。 每組包括兩種類型的記錄：所有者記錄和成員記錄。

(iii) Hierarchical data model

(iii)分層數據模型

In the hierarchical data, model data are represented by collections of records. Relationships among data are represented by links. In this model, tree data structure is used. There are two concepts associated with the hierarchical model segments types and parent-child relationships.

在分層數據中，模型數據由記錄的集合表示。 數據之間的關系由鏈接表示。 在此模型中，使用樹數據結構。 有兩個與層次模型段類型和父子關系相關的概念。

Advantages of Hierarchical data model

分層數據模型的優點

• Since the database is based on the hierarchical structure the relationships between the various layers are logically simple.

  由于數據庫基于層次結構，因此各層之間的關系在邏輯上很簡單。

• The hierarchical data model was the first database that offered the data security that is provided by DBMS.

  分層數據模型是第一個提供DBMS提供的數據安全性的數據庫。

• The Hierarchical database model is based on the parent-child relationships.

  分層數據庫模型基于父子關系。

• It is very efficient one when the database contains a large number of one-to-many relationships.

  當數據庫包含大量的一對多關系時，這是一種非常有效的方法。

2)基于對象的數據模型 (2) Object based data model)

In the object-based data model, the database is organized in real-world objects of several types. A number of fields or attributes are defined in each object. The two most popular object-based data models are:

在基于對象的數據模型中，數據庫以幾種類型的實際對象進行組織。 每個對象中定義了許多字段或屬性。 兩種最流行的基于對象的數據模型是：

(i) Object oriented model

(i)面向對象模型

The object-oriented model is based on a collection of objects. An object contains values stored in instances variable within the object. An object contains bodies of code that operate on the object.

面向對象的模型基于對象的集合。 對象包含存儲在對象內的實例變量中的值。 對象包含對對象進行操作的代碼主體。

Advantages of object oriented data model

面向對象數據模型的優點

• It represents relationships explicitly supporting both navigated and associative access to information.

  它表示明確支持導航和關聯信息訪問的關系。

• Object-oriented database systems are not suited for all applications.

  面向對象的數據庫系統并不適合所有應用程序。

• It is difficult to maintain when organizational information changes.

  組織信息發生變化時很難維護。

(ii) ER (Entity Relational model)

(ii)ER(實體關系模型)

The entity relational data model based on the perception of the real world that consist of a collection of basics objects and relationships between them. It is an object-based logical model. It is also high-level data model.

實體關系數據模型基于對現實世界的感知，該模型由一組基礎對象及其之間的關系組成。 它是一個基于對象的邏輯模型。 它也是高級數據模型。

翻譯自: https://www.includehelp.com/dbms/different-types-of-data-model-in-dbms.aspx

dbms支持哪幾種數據模型

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