Basic concepts of MySQL + database system structure + extended application + basic command learning

Chapter one ： Database system overview

One . Basic concepts of database system ：

1. Data and information ; Data is a symbolic record of things , Storage 、 User operation object . Presentation ： graphics 、 written words 、 Animation 、 voice 、 video .（ Data is the symbolic representation of signals ）

2. data —“ type ”“ value ”, data “ type ” Refers to the structure of data , value ： The specific value of data .

1. Qualitative 、 Quantitative expression .
2. Data is constrained by data type and value range .
3. Data has carriers and various forms .

1. Information has a certain meaning 、 After processing 、 Valuable data for decision making .

3 The relationship between information and data is summarized ： Data is the carrier of information , Information is the meaning of data . Data is the symbolic representation of signals , Information is described by data , It is also the interpretation of data semantics .

4. Data processing ：— Information processing — It refers to the collection of various forms of data 、 Storage 、 The whole process of dissemination and processing until new information output is generated .

1. The purpose of information processing ：

1. With the help of computer science to save and manage a large amount of responsible data , To make full use of information resources .
2. Starting from a large number of known raw data representing some information 、 extract 、 Export is of value to people 、 New information .

5. database

1. characteristic ： Permanent storage 、 Organized 、 Can share
2. The data in the database is structured —— Data model to organize .
3. storage medium ： Hard disk （ Commonly used ）、 Compact disc 、U disc — Can be a lot 、 Long term storage and efficient use of data .
4. Database is an organic data integration .（ Organic notes ： Dynamic change ）
5. database ： User database + System database （ The data dictionary , Description of the database structure ） Two parts .

6. Database management system

Definition ： management 、 System software that controls various database objects in a database .

interpretation DBMS：

1. Operating system ：DBMS It's the user , Built on the operating system , Need the operating system to provide services .（ process 、 Reading and writing 、 call 、 Memory ）
2. Count databases ：DBMS It's the manager , Between the operating system and the user （ It is software ）
3. DBMS It is the product of database .
4. function ： Data definition 、 Data manipulation （ Additions and deletions ）、 Database operation management 、 Establishment and maintenance of database

7. Database system （DateBase System,DBS）

Dbs= Computer system （ Software and hardware platform 、 people ）+DBMS+DB

The database system includes ： database 、DBMS、 Software platform and hardware support environment all kinds of personnel ;DBMS Supported by the operating system , Manage and maintain the database , Provide the user's operation interface to the database system .

   8. The information system ： By computer hardware 、 Network and communication equipment 、 Computer software 、 information resources 、 A man-machine integrated system composed of information users for the purpose of processing information flow .

Basic functions of information system ： Information input 、 Output and control 、 Storage 、 Handle .

9. The characteristics of database ：

1. Data structure
2. High data sharing 、 Low redundancy 、 Easy to expand
3. High independence
4. Data from DBMS Unified management and control

The database system consists of ： Hardware platform and database 、 Software 、（DBMS）、 personnel

Two 、 Database system structure

Adopt three-level mode structure ： External mode 、 Pattern 、 Internal mode composition

(01 Original picture )

（02 Comments ）

1. The relationship between three modules ：（ External mode 、 Pattern 、 Internal mode ） 

The database has only one internal schema 、 Internal mode is transparent to users .（ transparent ： The user is not visible ）

• 3、 ... and 、 Expand and extend ：

DB、DBMS and DBS What is the relationship between the three ？

DB： Refer to datebase（ database ）
DBS: Refer to datebase systerm ( Database system ）
DBMS: Refer to datebase mangement systerm（ Database management system ）
A database is a warehouse for storing data , Database management system is used to manage database . among , Database system is a general term , Include database 、 Database management system 、 Database administrator, etc , Is the largest category .
The database system is generally composed of 4 Component composition ：

（1） database （database,DB）
Database refers to the long-term storage in the computer , Organized , A collection of shareable data . The data in the database is organized according to a certain mathematical model 、 Description and storage , With less redundancy , High data independence and scalability , And can be shared for a variety of users .
（2） Hardware
The various physical devices that make up a computer system , Including external devices required for storage . The hardware configuration shall meet the needs of the whole database system .

（3） Software
Including the operating system 、 Database management system and application program .
Database management system （database management system,DBMS） It is the core software of database system , It works with the support of the operating system , Solve how to organize and store data scientifically , How to efficiently acquire and maintain data system software .

（4） personnel
There are mainly 4 class . The first category is system analysts and database designers , The second category is application programmers ; The third category is end users ; The fourth type of users are database administrators .
DBA The specific responsibilities of include ： The information content and structure in the specific database , Determine the storage structure and access strategy of the database , Define the security requirements and integrity constraints of the database , Monitor the use and operation of the database , Responsible for database performance improvement 、 The reorganization and reconstruction of database , To improve the performance of the system .

Four 、 Basic code command practice

（ Basic commands ）