SQLserver principle database (Database System Overview)

Copyright Notice: Copyright: @@ individual all https://blog.csdn.net/y20_20/article/details/90896157

Database System Overview

table of Contents

First, the history of database technology development

1. Data processing technology
2. Three stages of development of database technology

Second, the database system components

1. database
2. Database Management Systems
3. Database Application System
4. Database Users

Third, the architecture of the database

1. Three mode structure of the database
2. Two image database

Fourth, the Progress database technology

1. Distributed database
2. Object-Oriented Database
3. Multimedia Database
4. database
5. Data Mining
6. Big Data

Content section

First, the history of database technology development

1, data processing techniques

• Data: Symbol recorded description of things, manifested in the form of various types of information. For example: text, graphics, sound, etc.
• Data processing: refers to the information collection, collation, storage and use
• The purpose of data processing: analysis, induction, reasoning the link between the data and the data itself has a law in advance of the effective resources

2, database technology three stages of development:

• The reason three stages: With the development of computer hardware and software, database technology is also developing, from data management perspective, is divided into three stages
• The first stage : Artificial management phase (mainly for scientific computing)
  divided a reason : From a hardware point of view, there was no hard drives and other storage devices made direct deposit; From a software perspective, there was no operating system, no software to manage data, data processing using the batch
  is divided for two reasons : applications and data are not independent, the data processing carried by its own application

Correspondence between the applications and data: one correspondence, the following

Application 1 <-> data set 1
Application 2 <-> 2 data set
Application 3 <-> Data Group 3

• The second stage : the file system stage (at the scientific computing also used extensively for management)
  division One reason : the hardware, the disk become a major external memory; software, operating system and the emergence of high-level language, not only on the batch file handling leveling process can also be real-time processing
  division for two reasons : organized and stored as files, data and applications stored separately, both have a certain independence

The relationship between applications and file system data:

Phase III : Phase database system
division One reason : With the development of computers, high-capacity disk, the file system has been unable to meet human needs for management of large amounts of data, so there is a database system features: the ability to unify management and sharing data
characteristics database system:
1, structured data: the fundamental difference between the data and the file system is structured. DBMS for data that is not in an application, but for the entire application system
2, the higher data sharing: Because the structured data, the data may be a plurality of users, multiple applications concurrently shared
3, higher data independence: the application does not change with data storage structure, independent of each other and the data application that it does not exist between the interdependencies
4, there DBMS unified data management and control:
i.e. a plurality of concurrent users as shared, can simultaneously access the data in the database, even while accessing the same data in the database, so the DBMS must decency control data;
DBMS security mechanisms: (1) illegal authorization to prevent unauthorized access to data; ( 2), data integrity and consistency protection; (3), data backup and recovery

Applications and data correspondence database system diagram:

Composed Second, the database system

1, the database

• Database Definition: an organized long-term storage in the computer, a set of data that can be shared
• Database: contains data describing things not only itself, but also contact the relevant things
• 数据库中的数据已文件的形式存储在存储介质上

2、数据库管理系统（DBMS）：

• 是数据库系统的核心，是为了数据库的建立、使用和维护而配置的软件，建立在操作系统上
• 为用户和应用程序提供访问数据的方法，包括增删改查和各种数据控制等。总之对数据库的所有操作基本都是在DBMS中完成
• 数据库系统的功能主要包括：
  1、数据定义和操纵功能：对数据库中的对象进行定义，操纵数据库中的数据
  2、数据库运行控制功能：对数据库的运行进行管理是数据库管理系统运行时的核心部分，包括并发控制、安全性检查、完整性约束条件的检查和执行、数据库的内部维护等。所有访问操作都要在控制功能下进行
  3、数据库的组织、存储和管理：如何组织、存储和管理数据字典、用户数据、存取路径等多种数据，能提高效率
  4、建立和维护数据库：数据库的备份和恢复、数据库的重组值和重构造、性能的监视与分析等

3、数据库应用系统： 但凡使用数据库技术管理其数据的系统，都称之为数据库应用系统
4、数据库用户：

• 终端用户：数据库使用者，是通过应用程序使用数据库，不需要懂数据库的那群人
• 应用程序员：在数据库的基础上开发应用程序给终端用户使用的人
• 数据库管理员：专门管理数据库，让数据库正常运行的那群人

三、数据库的体系结构

1、数据库的三级模式结构： 保障数据和程序的独立性，因而DBMS将DB的体系结构划分为三级模式

1. 模式（概念模式或者逻辑模式）：对数据库中全部数据的逻辑结构和特征的描述，是所有用户的公共数据视图。一个数据库只有一个模式
2. 内模式（存储模式或者物理模式）：对数据物理结构和存储方式的描述，一个数据库只有一个内模式
3. 外模式（子模式或者用户模式）：局部数据的逻辑结构和特征的描述，模式的子集。一个数据库可以有多个外模式

三级模式结构图：

2, two image databases: three abstract pattern is made by the DBMS, for the realization of contact and converted three levels of abstraction, requiring two modes

1. External mode / image mode: a correspondence relationship defined outside of the patterns and pattern. Mode and external mode-to-many relationship. The image data and programs to ensure the independence of the logic, referred to as logical data independence
2. Mode / the image mode: a correspondence relationship with the logical structure defined global database storage structure. Because the model is unique within the model, so the model / model within only one image, when the data storage structure is changed simply by changing the appropriate mode can guarantee constant mode, the application does not need to be changed, so to ensure that the data and programs physical independence between, referred to as physical data independence
3. The core of the two images is to ensure that the external mode unchanged

Fourth, the Progress database technology

1, a distributed database: computer distribution has a complete copy of the DBMS, distributed over the network these computers are connected together to form a complete, global large database
main features of distributed databases:

1. Data are distributed: each computer interconnected by a network
2. Logically related data: data on multiple computers belong to a database system, there is a correlation between correlation data
3. Autonomy node: Each node is a stand-alone computer

2, object-oriented database: database technology and the combination of object-oriented. First, a database, database system, the basic functions, followed by an object-oriented system
** 3, the multimedia database: ** database and multimedia product of the combination.
** 4 Data Warehouse: ** subject-oriented design of
5, Data Mining: Data mining is to extract from the large amount of data or "mining" knowledge
6, Big Data: the definition of mass data.