Shulou(Shulou.com)05/31 Report--

This article mainly explains "what is the concept of database". The content of the explanation is simple and clear, and it is easy to learn and understand. let's follow the editor's train of thought to study and learn "what is the concept of database"!

Data storage mode

The storage of computer data (Data) generally takes the hard disk as the data storage space resource, so as to ensure that the data in the computer can be preserved continuously. For data processing, database-related technologies are generally used to ensure the efficiency of data processing.

The use of database management mode not only improves the efficiency of data storage, but also improves the security of data at the storage level. The classified storage mode makes the data management more secure and convenient, realizes the call and comparison of the data, and facilitates the use of query and other operations.

What is a database?

Database is an effective technology of data management, which is an orderly collection of data, which is stored in a structured data table. The data tables are related to each other, reflecting the essential relationship between objective things. Database can effectively help an organization or enterprise to manage all kinds of information resources scientifically.

Data is the basic object stored in the database, and it is the physical symbols arranged and combined in a certain order. Data can be expressed in many forms, such as numbers, text, images, and even audio or video, which can be digitized and stored in the computer.

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

In daily life, people can directly use Chinese, English and other natural languages to describe objective things. In the computer, it is necessary to abstract the characteristics of interest in these things and form a record to describe them.

For example, in the student file, the student information is composed of student number, name, sex, age, place of origin, contact number and so on, so a record composed of these specific eigenvalues is a student's information data, such as "2016010102, Zhang San, male, 26, Shanxi, computer College, 185 *".

It is worth noting that the description form of the data can not fully express its content and needs to be explained. For example, for the above student record, people who understand its meaning will get the following information: Zhang San's student number is 2016010102, he is 26 years old, he is from Shanxi, he is studying in the computer school, and his contact number is 185; those who do not understand its semantics cannot understand its meaning. Therefore, the data and the interpretation of the data are inseparable, the interpretation of the data refers to the explanation of the meaning of the data, and the meaning of the data is also called the semantics of the data, so the data is inseparable from its semantics, and the data without semantics is meaningless and incomplete.

Storage structure of database

The storage structure of the database refers to the representation of physical data and logical data in the database, and the description of the mapping between physical data and logical data. In database technology, two forms can be used to describe objective data: physical data description and logical data description. The conversion between physical data and logical data is realized by database management system.

Physical data description

Physical data description refers to the way the data is stored on the storage device. Physical data is the data actually stored on the storage device, which is also known as physical records. According to the location of physical record storage, it can be divided into ordered storage and disordered storage.

In physical data description, the data description terms used include the following.

Bit (bit): a binary unit is called a bit, and the bit can only be 1 or 0.

Byte: 8 bits are called a byte and can hold a character corresponding to the ASCII code.

Word (word): several bytes make up a word. The number of binary bits contained in a word is called word length, and the word length of many computers is different. For example, the word length of a computer can be 8 bits, 16 bits, 24 bits, 32 bits, and so on.

Block: the smallest unit of information exchanged between internal and external memory, also known as physical blocks or physical records. The size of each block is usually 256bytes, 512bytes, 1024 bytes, etc.

Volume (volume): all the useful information that can be loaded by an input / output device, for example, a tape of a tape drive is a volume, and a disk group of a disk device is a volume.

Unordered storage (unordered): data records are stored in the order in which they are inserted.

Logical data description

Logical data description refers to the data form used by users or programmers to operate. Logical data is an abstract concept that reflects and records the objective real world. These data can also be called logical records.

Logical data consists of two levels, one is the description of the objective reality information world, and the other is the description of the data in the database management system.

The terms used in the description of the objective reality information world include the following.

Entity (entity): what exists in objective reality is described by entity. Entities can not only be concrete and tangible objects, but also abstract and invisible objects. For example, a book is a tangible object, and the process of borrowing a book is an invisible object.

Entity set (entities): a set of similar entities with exactly the same characteristics is called an entity set. For example, all the books in a library are a physical collection, and all the borrowing processes of the library are also a physical set.

Attribute: the property of an entity is called an attribute. Each property has a range of values that can be integer type, floating point type, character type, date type, and so on. For example, the attributes of physical books include book title, book number, publication date, page number, price, publishing house, and so on. The corresponding ranges of these attributes are character type, character type, date type, integer type, floating point type, character type and so on.

Identifier: an attribute or set of attributes that uniquely identifies each entity. For example, the book number attribute of a book is the identifier of the physical book, and the identifier of the borrowing process entity includes two attributes: the library card number and the book number.

These logical data will eventually be converted into physical data through the database management system. What are the terms that describe logical data in a database management system?

Let's take the relational database management system as an example.

Data item (data item): also known as field, marks the smallest unit of information that can be named for an entity attribute. Data items are generally named using the descriptive name of the attribute. These names can be Chinese, English or Hanyu Pinyin.

Tuple: also known as record, and the collection of data items is called tuple. A tuple represents a specific entity.

Relation: in a relational database system, a set of tuples of the same class is called a relationship. Relationships are suitable for describing a set of entities, which includes all tuples of an entity set. For example, all books can form a books relationship.

Key code (key): in a relational database system, a key code that uniquely identifies data items or combinations of data items for each tuple in a relationship.

After the description of two layers of logical data, the objective entity is finally transformed into the actual stored physical data.

The role of Database in Development

From the point of view of database system application, the common operation and application structures of database system are client / server structure and browser / server structure.

In the client / server (Client/Server,C/S) structure, database users (such as DBA, programmers) connect to the database management system through command line clients, graphical interface management tools or applications, and can query and process all kinds of data stored in the underlying database through the database management system.

Database users interact directly with command line clients, graphical interface management tools or applications, but not with the database management system.

In this structure, command line clients, graphical interface management tools or applications, such as "client" or "foreground", mainly complete the task of interacting with database users, while the database management system is called "server" or "background", which is mainly responsible for data management. This structure is often referred to as the "Cramp S" structure.

In client / server mode, the client and server can work on the same computer at the same time, which is called "stand-alone mode"; it can also be run in "network mode". That is, the server is installed and deployed on one or more hosts in the network.

For the development of client applications, the commonly used language tools are Visual C++, Delphi, .NET Framework, Visual Basic, Python and so on.

Database can effectively store data, read data, find data is more convenient, in fact, those management software is through the software interface to the internal database to add, delete, change, check the operation.

Thank you for your reading. the above is the content of "what is the concept of database". After the study of this article, I believe you have a deeper understanding of what the concept of database is, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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.