Shulou(Shulou.com)06/01 Report--

What the editor shares with you today is the introduction of the database management system. I believe many people do not know much about it. In order to let you know more about the database management system, I have summarized the following contents for you. Let's look down together. I'm sure you'll get something.

Six Properties of Database relationship

(1) columns are homogeneous, that is, the components in each column are of the same type of data and come from the same domain.

(2) different columns can come from the same field, each of which is said to be an attribute, and different attributes should be given different attribute names.

(3) the order of the columns does not matter, that is, the order of the columns can be exchanged at will.

(4) any two tuples cannot be exactly the same.

(5) the order of rows does not matter, that is, the order of rows can be exchanged at will.

(6) components must take atomic values, that is, each component must be an inseparable database.

Basic Concepts of Database system

Data: it is actually a symbolic record that describes things.

The characteristics of the data: there is a certain structure, there are types and values, such as integer, real, character and so on. The value of the data gives a stereotyped value, such as an integer value of 15.

Database: a collection of data, with a unified structure and stored in a unified storage medium, is the integration of a variety of application data, and can be shared by various applications.

The data stored in the database is stored according to the data mode provided by the data, which has the characteristics of integration and sharing.

Database management system: a system software that is responsible for data organization, data manipulation, data maintenance, control and protection and data services in the database, is the core of the database.

Database management system functions:

(1) data schema definition: building its data framework for the database

(2) physical construction of data access: to provide effective access methods and means for the physical access and construction of data patterns.

(3) data manipulation: provide convenience for users to use the data of the database, such as query, insertion, modification, deletion, as well as simple arithmetic operations and statistics.

(4) definition and inspection of data integrity and well-being

(5) concurrency control and fault recovery of database

(6) data services: such as copy, rollover, reorganization, performance monitoring, analysis, etc.

In order to accomplish the above six functions, the database management system provides the following data languages:

(1) data definition language: responsible for data schema definition and data physical access construction

(2) data manipulation language: responsible for data manipulation, such as query and add, delete, change, etc.

(3) data control language: responsible for data integrity, security definition and check, concurrency control, fault recovery and so on.

Data languages have two structural forms according to the way they are used: interactive commands (also known as self-contained or autonomous languages) host languages (which can generally be embedded in some host languages).

Database administrator: a professional manager who plans, designs, maintains and monitors the database.

Database system: a running entity composed of database (data), database management system (software), database administrator (personnel), hardware platform (hardware) and software platform (software).

Database application system: it is composed of database system, application software and application interface.

File system phase: provides simple data sharing and data management capabilities, but it does not provide complete, unified, management and data sharing capabilities.

Hierarchical database and mesh database system stage: provides a strong support for unifying and sharing data.

Relational database system phase

The basic characteristics of database system: data integration, high data sharing and low redundancy, data independence (physical independence and logical independence), unified data management and control.

The three-tier mode of the database system:

(1) Conceptual schema: description of global data logical structure in database system, common data view of all users.

(2) external mode: also known as submode and user mode. Is the user's data view, that is, the data pattern that the user sees

(3) Internal mode: also known as physical mode, it gives the physical storage structure and physical access method of database.

Two-level mapping of the database system:

(1) Mapping from conceptual schema to internal schema.

(2) the mapping from external schema to conceptual schema.

On the introduction of the database management system is shared here, I hope that the above content can have a certain reference value for everyone, you can learn to apply. If you like this article, you might as well share it for more people to see.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.