What are the three basic characteristics of a database?

The three basic characteristics of a database are: 1. Data structuring. Data structuring is the fundamental difference between databases and file systems; 2. Data has high sharing, low redundancy, and is easy to expand; 3. , High data independence, including physical independence of data and logical independence of data.

The operating environment of this tutorial: windows7 system, mysql8 version, Dell G3 computer.

Data structuring

Data structuring is the fundamental difference between database and file system. In a file system, the records of independent files are internally structured. The simplest form of a traditional file is a collection of records of equal length and format. For example: a student's personnel record file, each record has a record format as shown in Figure 1.

2. Data has high sharing, low redundancy, and is easy to expand

The database system describes the data from an overall perspective. The data is no longer oriented to a certain application but to the entire system. Therefore, the data It can be shared by multiple users and multiple applications. Data sharing can greatly reduce data redundancy and save storage space. Data sharing can also avoid incompatibilities and inconsistencies between data. The so-called data inconsistency refers to the different values ​​of different copies of the same data. When using manual management or file system management, since data is stored repeatedly, it is easy to cause data inconsistencies when different applications use and modify different copies. Data sharing in the database reduces inconsistencies caused by data redundancy. Since the data is oriented to the entire system and is structured data, it can not only be shared and used by multiple applications, but also easily add new applications. This makes the database system highly flexible, easy to expand, and can adapt to various user requirements. Various subsets of the overall data can be used in different application systems. When application requirements change or increase, new requirements can be met by re-selecting different subsets or adding part of the data.

3. High data independence

Data independence is a commonly used term in the database field, including the physical independence of data and the logical independence of data. Physical independence means that the user's application is independent of the data in the database stored on disk. In other words, the storage of data in the database on the disk is managed by the DBMS. The user program does not need to understand it. All the application program has to deal with is the logical structure of the data. In this way, when the physical storage of the data changes, the application program does not need to Change. Logical independence means that the user's application program and the logical structure of the database are independent of each other. That is to say, if the logical structure of the data changes, the user program can also remain unchanged. The independence of data and programs separates the definition of data from the program, and the DBMS is responsible for data access, thus simplifying the preparation of application programs and greatly reducing the maintenance and modification of application programs.

Supplement:

Data is managed and controlled by the DBMS.

The sharing of the database is concurrent sharing, that is, multiple users can simultaneously Access data in the database, and even access the same data in the database at the same time. To this end, DBMS must also provide the following data control functions:

(1) Data security (Security) protection

Data security refers to protecting data to prevent illegal The use results in data leakage and destruction. Each user can only use and process certain data in certain ways according to regulations.

(2) Data integrity (Integrity) check

Data integrity refers to the correctness, validity and compatibility of the data. Integrity checking controls the data within a valid range or ensures that certain relationships between data are met.

(3) Concurrency control

When concurrent processes of multiple users access and modify the database at the same time, mutual interference may occur and incorrect results may occur, or the database may be damaged. Integrity is compromised, so concurrent operations by multiple users must be controlled and coordinated.

(4)Database Recovery(Recovery)

Hardware failure, software failure, operator error, and intentional damage of the computer system will affect the accuracy of the data in the database, and even cause the loss of part or all of the data in the database. The DBMS must have the function of recovering the database from an error state to a known correct state (also known as a complete state or a consistent state). This is the recovery function of the database. The corresponding relationship between the application and the database during the database management phase can be represented by the structure shown in Figure 1-3. See the book. A database is an organized, large-scale, shared collection of data stored in a computer for a long time. It can be shared by various users with minimal redundancy and high data independence. DBMS performs unified control on the database during database establishment, operation and maintenance to ensure data integrity and security. It also performs concurrency control when multiple users use the database at the same time, and recovers the system after a failure. The emergence of database systems has shifted information systems from being centered on programs that process data to a new stage centered around shared databases. This not only facilitates the centralized management of data, but also facilitates the development and maintenance of applications, improves data utilization and compatibility, and improves the reliability of decision-making. At present, databases have become an inseparable and important part of modern information systems. Databases with millions or even billions of bytes of information have become ubiquitous in information systems in science and technology, industry, agriculture, commerce, service and government departments

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