IOS _ database 2 _ basic knowledge, basic knowledge of ios

IOS _ database 2 _ basic knowledge, basic knowledge of ios









































Basic Database knowledge

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Basic Database knowledge

Chapter 1 basic database knowledge
This chapter focuses on concepts, including basic concepts of databases, development of database technology, data models, and relational data.

Section 1: information, data and data processing

I. Information and Data:
1. Information: reflects the existence or motion of things in the real world. Or, the information is a type of data that has been processed as a specific form.
The main characteristics of information are: information transmission requires a material carrier, and information acquisition and transmission consumes energy; information can be perceived; information can be stored, compressed, processed, transmitted, shared, disseminated, regenerated, and added-value
2. Data: data is the carrier and specific manifestation of information, and information does not change with changes in data forms. Data is represented by text, numbers, images, and sounds.
3. Relationship between data and information: Generally, data and information are regarded as a concept without distinction.
Ii. data processing and data management technology:
1. Data Processing: data processing is a general term for various forms of data collection, storage, processing and transmission activities.
2. Data management: data collection, classification, organization, encoding, storage, retrieval, transmission, and maintenance are the basic operations for data processing. Data management is the core issue of data processing.
3. The question of database technology is not how to scientifically manage data.
4. Three Phases of Data Management Technology: manual management, file management, and database systems.

Section 2: Development of database technology

I. development of databases: the development of databases has gone through three stages:
1. hierarchical and mesh:
The representative product is the level model database management system IMS developed by IBM in 1969.
2. Relational Database:
Currently, most databases use relational databases. In 1970, E. F. Codd, a researcher at IBM, proposed a relational model. The products are sysem R and Inges.
3. Third-generation databases will feature richer data models and more powerful data management functions, and provide new applications that are difficult to support by traditional database systems. It must support object-oriented, open, and can be used on multiple platforms.
Ii. Development Trend of database technology:
1. Impact of object-oriented methods and technologies on database development:
Database researchers drew on and absorbed the object-oriented methods and technologies and proposed an Object-oriented Data Model.
2. The combination of database technology and multidisciplinary technology:
3. Database Technology for specialized application fields
Iii. Composition of database systems:
Database System (DBS) is a computer system that uses database technology and provides database management functions. It consists of hardware, software, databases, and various personnel.
1. Database (DB ):
A database is a set of data associated with external memory of a computer. It is the core and management object of the database system, and its data is integrated, shared, and redundant.
2. Database Management System (DBMS ):
The database management system is the software used to maintain and manage databases. It is the interface between databases and users. As the core software of the database, it provides commands and methods for establishing, operating, and maintaining the database.
3. Applications:
You can write programs that process data in the database.
4. Computer Software:
5. Computer Hardware:
Including CPU, memory, and disk. Requires sufficient memory to store core modules of the operating system and database management system as well as database buffering; large enough disks can directly access and back up data; Master channel capability; supports networking for data sharing.
6. Various personnel.
Iv. Features of the database system:
1. Data Sharing:
2. Data structuring for the entire Organization:
Data no longer belongs to a specific application, but is organized into a structured whole according to a certain model. It describes the characteristics of data and the relationships between data.
3. Data independence:
4. controllable data redundancy:
5. Unified Data Control:
Data security control: it refers to taking certain security and confidentiality measures to ensure that data in the database is not accessed by illegal users, resulting in Data leaks and damages;
Data Integrity Control: it is the correctness, validity, and compatibility of the index data.
Concurrency Control: when multiple users access data, take necessary measures for data protection;
Data Recovery: system... the remaining full text>