Database technology is a core technology of information system.It's a computerauxiliaryThe method of managing data, which studies how to organize and store data, and how to acquire and process data efficiently.
Database technologyIt is a technology to process, analyze and understand the data in the database by studying the basic theories and implementation methods of database structure, storage, design, management and application.Namely, database technology is a software science that studies, manages and applies databases.
The object of database technology research and management is data, so the specific contents involved in database technology mainly include: building corresponding databases and data warehouses according to the specified structure through the unified organization and management of data;utilizeDatabase management systemAnd data miningsystem designIt can add, modify, delete, process, analyze, understand, report and print data in the databasedata managementAnd data mining application system;Finally, the application management system is used to realize data processing, analysis and understanding.
Database technology is a core technology of information system.It is a method of computer aided data management. It studies how to organize and store data, and how to obtain and process data efficiently.Through researchdata baseThe basic theory and implementation method of the structure, storage, design, management and application of thedata baseIndataTechniques for processing, analysis, and understanding.Namely, database technology is a software science that studies, manages and applies databases.
Database technology is an important part of modern information science and technology, and is the core of computer data processing and information management system.Database technology has researched and solved the problem of effective organization and storage of large amounts of data in the process of computer information processingdatabase systemReduce data storage redundancy, realize data sharing, ensure data security, and efficiently retrieve and process data.[1]
Background
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Database technology came into being in the late 1960s and early 1970s. Its main purpose is to effectively manage and access a large number of data resources. Database technology mainly studies how to store, use and manage dataOver the years, database technology and computernetwork techniqueThe development of database technology has infiltrated and promoted each other, and has become the two major fields of rapid development and wide application in today's computer field. Database technology is not only applied to transaction processing, but also further applied to information retrieval, artificial intelligence,expert system,Computer Aided DesignEtc
Development application
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Since the late 1960s, database technology has developed for more than 30 years.In the course of more than 30 years, people have made brilliant achievements in the theoretical research and system development of database technology, and have begun to pay attention to the new generationdatabase systemIn-depth research.Database system has become an important part of modern computer system.
The database was originally used as the basis for large-scale transaction processing in large companies or organizations.Later, with the popularity of personal computers, database technology was transplanted to personal computers (PCs) for single user personal database applications.Then, because the PCWorking GroupInternally connected, the database technology will be migrated to the working group level.Today, databases areIntranetWidely used in.
In the mid-1960s, database technology was used to solve the problem of file processing system.At that time, the database processing technology was still very fragile, and applications often could not be submitted.1970srelational model The birth of the provides database experts with standard methods for constructing and processing databases, and promotes the development and application of relational databases.In 1979, Ashton Tate introduced the microcomputer product dBase II, which is calledRelational Database Management System, from this databaseTechnology migrationTo a personal computer.From the mid-1980s to the late 1980s, end users began to useLANTechnology connects independent computers into a network, and terminals share databases, forming a new type of multi-user data processing, called client/server database structure.Today, database technology is being used to combine with Internet technology toIntranet, departmental LAN and even WWW.
Database technology is an important part of modern information science and technology. It is the computer data processing andmisThe core of.Database technology studies and solves the problem of computerinformation processingThe problem of effective organization and storage of a large amount of data in the process reduces data storage redundancy, realizes data sharing, ensures data security, and efficiently retrieves and processes data in the database system.The fundamental goal of database technology is to solve the problem of data sharing.
development
Data management technology is to classify, organize and code data,inputThe development of data management technology has roughly gone through the following three stages: manual management stage;File system stage;database systemPhase
Manual management stage
Before the 1950s, computers were mainly used for numerical calculation. From the perspective of hardware at that time, there were only paper tapes, cards and tapes in external storage, and there was no direct access device;From the perspective of software (in fact, the overall concept of software was not formed at that time), there was no operating system and software for managing data;From the perspective of data, the amount of data is small, the data has no structure, is directly managed by users, and the data lacks logical organization,Data dependencyLack of independence for specific applications
File System Phase
From the late 1950s to the mid-1960s, data storage devices such as magnetic drums and disks appeareddata processing systemIt has developed rapidly. This data processing system is based ondata organization As mutually independent data files, the system can access the files according to their names, access the records in the files, and modify, insert, and delete the files. This is the file system. The file system implements the structure within the records, that is, it gives the relationship between various data within the records. However,As a whole, the file is unstructured. Its data is oriented to specific applications, so the data sharing, independence, redundancy and cost of management and maintenance are poor
In the late 1960s, data management technology such as database appeared. Database is characterized by that data is no longer only for a specific application, but for the whole organization, with overall structure, high sharing, low redundancy, certain independence between programs and data, and unified control of data
data model
⒈2.1data modelThe concept and element data model ofdatabase systemData model usually includes three elements:
⑴ Data structure. Data structure is mainly used to describe the static characteristics of data, including the structure of data and the relationship between data
(2) Data operation. Data operation refers to various data access methods that can query, modify, delete existing data or add new data in the database, and includes rules related to data access
⑶ Data integrity constraints. Data integrity constraints consist of a set of integrity rules
1. 2.2 Common data models
The most common data models in the field of database theory mainly include hierarchical model, mesh model andrelational model 3 kinds
⑴ Hierarchical Model. Use of Hierarchical Modeltree structureTo represent data and the relationship between data
⑵ Network Model. The network model uses the network structure to represent data and the relationship between data
⑶ Relational model. Relational model is the most mature in theory and widely useddata modelIn the relational model, data is stored in aLogical unitThe whole database is composed of several interrelated two-dimensional tables
1. 2.2 Common data models
At present, there are some popular and mature software products that can well support the relational data model. These products are also called relationalDatabase management system(Relational DataBase Management System, RDBMS). For example,MicrosoftMicrosoft Access andMS-SQL Server, Sybase of Sybase,OracleOracle and IBM DB2. Microsoft Access is a small and medium-sized database management system, which is suitable for general small and medium-sized enterprises;MS-SQL Server, Sybase and Oracle are basically large and medium-sized database management systems;DB2 is a large database management system, and has high and special requirements for computer hardware
technology
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Information Technology (IT) is one of the most frequently used terms nowadays. With the wide application of computer technology in industry, agriculture and daily life, it has been taken as one of the signs by more and more individuals and enterprises to catch up with the world trend.Database technology is an important support in information technology.Without database technology, people will be at a loss in the vast information world.
Database technology is an important branch of computer science and technology.Since the mid-1950s, computer applications have expanded from scientific research departments to enterprise management and government administrative departments, and people have increasingly high requirements for data processing.In 1968, the first commercializedmisIMS (Information Management System), since then, database technology has developed rapidly.Today, the Internet is increasingly accepted by people, and the importance of database technology, knowledge and skills has been fully amplified by the Internet.Today, databases have become information managementoffice automation 、Computer Aided DesignIt is one of the main software tools for applications such as to help people deal with various information data.
Development history
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data modelIt is the core and foundation of database technologydatabase systemThe division of development stages should be based on the development of data models.According to the development and evolution of data models, database technology has mainly gone through three development stages in the short 30 years from the beginning to the present: the first generation is the mesh and hierarchical database system, and the second generation is theRelational database systemThe third generation is a database system characterized by object-oriented data model.Database technology and network communication technology, artificial intelligence technologyObject-oriented programmingTechnologyParallel computingInterpenetration and organic combination of technologies have become an important feature of the development of contemporary database technology.
system
first generationdatabase systemIt is the level of research and development in the 1970sMesh databaseSystem.The typical representative of hierarchical database system is 1969IBMDevelopedhierarchical model OfDatabase management systemIMS. In the late 1960s and early 1970s, DBTG (Data Base Task Group), a database task group affiliated to CODASYL (Conference on Data System Language), put forward several reports, known as DBTG reports.DBTG report determines and establishes many concepts, methods and technologies of mesh database system, and is a typical representative of mesh database system.Under the guidance of DBTG ideas and methods, the implementation technology of database system has been maturing, and many commercial database systems have been developed, all of which are based onhierarchical model andMesh modelOf.
so to speak,Hierarchical databaseIs the pioneer of database systems, andMesh databaseIt is the founder of database concept, method and technology.
database system
Second generationdatabase systemyesRelational database system。1970IBMEdgar F. Codd, a researcher in the San Jose Research Laboratory ofrelational model 》And put forward the relationshipdata model, created the relational database method and relational database theory, and laid a theoretical foundation for relational database technology.Edgar F. Codd was awarded ACM in 1981Turing Award, in recognition of his outstanding contributions to relational database research.
The 1970s was the era of theoretical research and prototype development of relational databases, with System R developed by San Jose Research Laboratory of IBM and Ingres developed by Berkeley University as typical representatives.A large number of theoretical achievements and practical experience have finally made relational databases move from laboratory to society. Therefore, people call the 1970s the database era.In the 1980s, almost all newly developed systems were relational, and many commercialization with excellent performance emergedRelational Database Management System, such as DB2, IngresOracle、Informix、SybaseEtc.These are commercially availabledatabase systemThe application of database technology has increasingly been widely applied to enterprise management, information retrieval, and assistancepolicy decisionIt has become the basic technology to realize and optimize the information system.
Third generation database system
Since the 1980s, the great commercial success of database technology has stimulated the rapid growth of demand for database technology in other fields.These new fields have opened up a new world for database applications, and put forward some newdata managementThe demand of database technology promotes the research and development of database technology.
In 1990, the Advanced DBMS Function Committee published the Third Generationdatabase systemDeclaration, proposing the third generationDatabase management systemIt should have three basic characteristics:
It shall support data management, object management and knowledge management.The technology of the second generation database system must be maintained or inherited.It must be open to other systems.
Four directions
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The scale will develop to both ends - the big ones will become bigger and bigger, and the small ones will become smaller and smaller.The so-called large refers to the scale of enterprise level databases.In the first 10 years, most of the data stored in the database was measured by GB, and dozens of GB were already huge.Today, the amount of data added by Guangdong Mobile every month has been measured in terabytes. Within three years, many enterprises will store petabytes of data.With the increasing amount of data, it needs a larger database as support, which is one of the development directions of database.On the other hand, the database will become smaller and smaller.Today,SybaseThe database of has been installed in high-end Casio watches, which record weather conditions, air pressure, wearer's blood pressure, heartbeat and other data.This kind of database does not require a large amount of data storage, but requires fast response in the case of low computational load, and can adapt to changes in the external environment.Change of storage mode from row to column.Previously, databases were stored in the form of rows for the simple reason that users need to read and store single data.Today, simple data recording is not enough to support the development of enterprises. What enterprises need more is data analysis andpolicy decisionsupport.Then, it is meaningless to simply look at a record. Instead, it is necessary to count a certain item of all data for analysis. This is the concept of column.withChina MobileFor example, hundreds of millions of users, monthly terabytes of data, which are Ⅵ P users, how to provide exclusive services according to their needs, and what preferential policies should be formulated for those users in the M-Zone. In addition to looking at the phone charges, can we also tap into their consumption characteristics and carry out more targeted business promotion activities?These are not the problems of looking at a piece of data, but need to operate on the columns frequently.It is expected that within half a year, all major database manufacturers will launch databases listed as storage mode.Unstructured dataStill cannot be included in the database.Speaking of this, we may all think that I am going against the tide. Now many database vendors can accept unstructured data such as images and videos,SybaseWhy should we stick to structured data?In fact, I think that unstructured data still needs to be structured if it wants to enter the database, but this structured method is different for different manufacturers, and has made great progress and improvement compared with the past.Previously, we recorded the file name of an image. If a person's name is mentioned in the file name, the image can be found when querying the entire database.This is very unscientific, because many unstructured data files cannot be named completely.Now, when we change unstructured data into structured data, we are actually describing the image with structured data, such as using points and positions to record each pixel of the image.Once a query is required, it can be compared according to the combined records of pixels to filter out all the data that meet the comparison requirements.That's itUnstructured dataIt is included in the database in a structured way, and can accept queriesretrievalAnd so on.Database and data warehouse will be separated.Many database manufacturers believe that one database is good, and it can be used for real-time transactions and data analysis.However, many users now need the database to provide real-time transaction function in the foreground, and need a fast response speed. In the background, they need to set up some rules for data analysis and business intelligence analysis.SybaseIt is believed that these two databases should be in two formats. After all, their functions are different.Therefore, in terms of product settings, Sybase has two types: transactional database and analytical database.
Development trend
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Development Mainstream of Next Generation Database Technology
In view of the existing limitations of relational database technology, there are three main views in the theoretical circle:
object-orientedSome scholars believe that the existing relational databases cannot describe the entities in the real world, while object-orienteddata modelBy absorbing the core concepts and basic ideas of the mature object-oriented programming methodology, it conforms to the general method of human understanding of the world and is more suitable for describing the real world.Some even predict that the future of database will be an object-oriented era.
Object-oriented relational database technologydatabase systemHowever, its concise modeling ability, limited data types, and restrictions on data structures in programming have become the bottleneck of the role of relational databases.Object oriented methodOriginated from programming language, it uses real world entity objects as basic elements to describe the complex objective world, but its function is not as flexible as database.Therefore, some scholars believe thatobject-orientedIt is a developing direction of database technology to combine the modeling ability of database and the function of relational database.
Object oriented database technology The advantage of object-oriented database is that it can represent complexdata modelHowever, because there is no unified data model and formal theory, there is a lack of strict data logic foundation.andDeductive databaseAlthough it has a strong mathematical logic foundation, it can only deal with plane data types.Therefore, some scholars put forward a new database technology deductive object-oriented database by combining the two, and pointed out that this technology may become the mainstream of the next generation database technology.
New Development Direction of Database Technology
Unstructured database is a new database theory based on Internet application, which is proposed by some researchers from the perspective of data model in view of the limitations of relational database model, such as too simple to express complex nesting needs and limited support data types.It supports duplicate fields, subfields, and variable length fields, and realizes the processing of variable length data and duplicate fields and variable length storage management of data items. It has advantages that traditional relational databases cannot match in processing continuous information (including full-text information) and unstructured information (duplicate data and variable length data).However, researchers believe that this database technology will not completely replace the current popular relational database, but it is a useful supplement to them.
Another Trend of Database Technology Development
Some scholars pointed out that the combination of database and subject technology will establish a series of new databases, such as distributed database, parallel database, knowledge base, multimedia database, etc. This will be an important development direction of database technology.Among them, many researchers focus on multimedia database and believe thatmultimedia technologyThe introduction of multimedia database and visualization technology will be a hot and difficult point in the development of database technology in the future.
Two directions of future database technology and market developmentdata warehouse On the basis of analyzing the development direction of various database manufacturers and the expanding status of application needs, some scholars in e-commerce put forward the view that database technology and market are developing in two directions: data warehouse and e-commerce.They pointed out that since last year, many industries such as telecommunications, finance, taxation, etc. have gradually realized the huge economic benefits of data warehouse technology for the macro development of enterprises, and have established data warehouse systems.The major vendors that provide large-scale data warehouse solutions in China areOracle、IBM、Sybase, CA, Informix and other manufacturers. The projects that have been successfully constructed and have recovered their investment mainly includeChina Merchants BankSystem and Guosen Securities System, etc.At present, scholars at home and abroad are continuing to deepen the research on data warehouse.At the same time, some scholars aim at the field of e-commerce from the perspective of database technology and market development. They believe that today'sinformation systemIt is gradually required to establish an application framework in a customer-centric way, so it is bound to require database applications to contact customers more widely. The Internet provides us with a very convenient connection way. Through the Internet, we can realize the so-called One One Marketing and One One business, and then realize E business.Therefore, e-commerce will become another direction of database technology development in the future.
Database technology for special application fieldsMany researchers have studied database technology from the perspective of practice and proposed database technologies suitable for application fields, such as engineering database, statistical database, scientific database, spatial database, geographical database, etc.Such databases do not change much in principle, but they are combined with certain applications, thus strengthening the system's ability to support relevant applicationsdata model, language and query.Some researchers believe that with the further research work and the application of database technology in practical work, database technology will develop more towards specialized application fields.
Basic concepts
Data and data processing
Data is a symbol used to describe various concrete things or abstract concepts in the real world, which can be stored and has a clear meaning, including numbers, words, graphics and sounds. Data processing refers to the sum of a series of activities to collect, store, process and disseminate various forms of data. One of its purposes is to extract from a large number of original data,Derive valuable information for people as the basis for actions and decisions;The second purpose is to use computer technology to scientifically store and manage complex and large amounts of data, so that people can easily and fully use these valuable information resources
data base
Database (DB) is stored on the computerAuxiliary memoryThe database has the following characteristics
⑴ Database is a data set with logical relationship and definite meaning
⑵ The database is designed, built and loaded for specific application goals. Each database has a group of users and serves the application needs of these users
⑶ A database reflects some aspects of objective things and needs to be consistent with the state of objective things
The Database Management System (DBMS) manages the databasesystems softwareIts function is to effectively organize and store data, acquire and manage data, accept and complete various data access requests proposed by users. It can support relationaldata modelRDBMS (Relational Database Management System)
The basic functions of an RDBMS include the following four aspects:
⑴ Data definition function: RDBMS providesData definition language(Data Definition Language, DDL). Using DDL, you can easily define the relevant content in the database. For example, you can define the database, table, field andIndexesDefine, create, and modify
⑵ Data manipulation function: RDBMS providesData manipulation language(Data Manipulation Language, DML). With DML, basic operations such as inserting, modifying, and deleting data can be realized in the database
⑶ Data query function: RDBMS provides Data Query Language (DQL), which can be used to query data in the database
⑷ Data control function: RDBMS providesData Control Language(Data Control Language, DCL). Using DCL, you can complete the database operation control functions, including concurrency control (that is, processing problems that may occur when multiple users use some data at the same time), security check, check and execution of integrity constraints, and internal database maintenance (such as automatic index maintenance)Many of the above functions of RDBMS can be accessed throughStructured Query Language(Structured Query Language, SQL)relational databaseThe basic syntax of SQL is the same in different RDBMS products. In addition, DDL, DML, DQL and DCL also belong to SQL
Database application system is also calleddatabase system, refers to a computer system with database technology support, which can realize the organized and dynamic storage of large amounts of relevant data, provide data processing andinformation resources sharing Functions of the service
All kinds of personnel mainly participate in the database application systemrequirement analysis, design, development, use, management and maintenance. They play different roles in the development, operation and maintenance of database application systems. Various personnel mainly include the following
In terms of its application mode, database technology mainly plays two roles
⑴ The role of information system development. Using database technology and Internet technology, combined with specific programming language, an information system can be developed to solve the problem of business data input and management. In the development of information system, the basic functions of RDBMS are mainly used, namely data definition function, data manipulation function, data query function and data control function
⑵ Data analysis and presentation. Use the data query function of RDBMS to conduct association, combination or level by level summary and analysis of data in the database, and display the analysis results in the form of tables, graphs or reports, so as to solve the problem of comprehensive utilization of business data
