作业帮急! 来一篇关于数据库概述的英语作文
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急! 来一篇关于数据库概述的英语作文
急! 来一篇关于数据库概述的英语作文
急! 来一篇关于数据库概述的英语作文
请google scholar 谷歌学术 -- database
或wikipedia 维基百科 -- database
以下为部分节选
A database consists of an organized collection of data for one or more uses,typically in digital form.One way of classifying databases involves the type of their contents,for example:bibliographic,document-text,statistical.Digital databases are managed using database management systems,which store database contents,allowing data creation and maintenance,and search and other access.
Database architecture consists of three levels,external,conceptual and internal.Clearly separating the three levels was a major feature of the relational database model that dominates 21st century databases.
The external level defines how users understand the organization of the data.A single database can have any number of views at the external level.The internal level defines how the data is physically stored and processed by the computing system.Internal architecture is concerned with cost,performance,scalability and other operational matters.The conceptual is a level of indirection between internal and external.It provides a common view of the database that is uncomplicated by details of how the data is stored or managed,and that can unify the various external views into a coherent whole.