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This article mainly introduces "what are the basic characteristics of the database". In the daily operation, I believe that many people have doubts about the basic characteristics of the database. The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful for you to answer the doubts about "what are the basic characteristics of the database?" Next, please follow the editor to study!

Database has three basic characteristics: (1) data structure, which is the fundamental difference between database and file system; (2) high sharing of data, low redundancy and easy expansion; (3) high independence of data, including physical independence and logical independence of data.

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

Data structure

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

two。 The data has high sharing, low redundancy and easy expansion.

The database system describes the data from an overall point of view, and the data is no longer for an application but for the whole system, so the data 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 incompatibility and inconsistency between data. The so-called data inconsistency means that different copies of the same data have different values. When using manual management or file system management, because the data is stored repeatedly, it is easy to cause data inconsistency when different applications use and modify different copies. Data sharing in the database reduces the inconsistencies caused by data redundancy. Because the data faces the whole system, it is structured data, which can not only be shared by multiple applications, but also easy to add new applications, which makes the database system flexible, easy to expand, and can adapt to a variety of user requirements. Various subsets of the overall data can be taken into different application systems, when the application requirements change or increase, as long as re-select a different subset or add a part of the data to meet the new requirements.

3. High independence of data

The independence of data is a common 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 stored in the database on disk. In other words, the storage of data in the database on disk is managed by DBMS, the user program does not need to understand, and the application only deals with the logical structure of the data, so that when the physical storage of the data changes, but the application does not need to change. Logical independence means that the logical structure of the user's application and the database are independent of each other, that is to say, the logical structure of the data has changed, and the user program can remain unchanged. The independence of data and program separates the definition of data from the program, and DBMS is responsible for the access of data, which simplifies the programming of the application and greatly reduces the maintenance and modification of the application.

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Data is uniformly managed and controlled by DBMS

Database sharing is concurrent sharing, that is, multiple users can access the data in the database at the same time, or even access the same data in the database at the same time. To do this, DBMS must also provide the following data control functions:

(1) data security (Security) protection

The security of data refers to the protection of data to prevent illegal use of data from leaking and destroying. So that each user can only use and process some data in certain ways according to the regulations.

(2) data integrity (Integrity) check

The integrity of data refers to the correctness, validity and compatibility of the data. Integrity check controls the data within a valid range, or ensures a certain relationship between the data.

(3) Concurrency control

When the concurrent processes of multiple users access and modify the database at the same time, they may interfere with each other and get wrong results, or the integrity of the database may be destroyed, so the concurrent operations of multiple users must be controlled and coordinated.

(4) Database recovery (Recovery)

The hardware failure, software failure, operator error and intentional destruction of the computer system will affect the correctness of the data in the database, and even cause the loss of some or all of the data in the database. DBMS must have the ability to restore a database from an error state to a known correct state (also known as a full state or consistent state), which is the recovery function of a database. The correspondence between the application and the database in the database management phase can be represented by the structure shown in figure 1-3. See the book. A database is a collection of organized, large and shared data stored in a computer for a long time. It can be shared by all kinds of users with minimum redundancy and high data independence. DBMS uniformly controls the database during the establishment, application and maintenance of the database to ensure the integrity and security of the data, and carries out concurrency control when multiple users use the database at the same time, and recovers the system after failure. The emergence of the database system makes the information system shift from the program centered on processing data to the new stage centered around the shared database. This is not only convenient for the centralized management of data, but also conducive to the development and maintenance of application programs, improving the utilization and compatibility of data, and improving the reliability of decision-making. At present, database has become an important and inseparable part of modern information system. Databases with millions or even billions of bytes of information have been ubiquitous in the information systems of science and technology, industry, agriculture, commerce, services and government departments.

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