文档介绍：外文原文
Database Management
Database (sometimes spelled database) is also called an electronic database, referring to any collections of data, or information, that is anized for rapid search and retrieval by puter. Databases are structured to facilitate the storage, retrieval modification and deletion of data in conjunction with various data-processing operations. Database can be stored on ic disk or tape, optical disk, or some other secondary storage device.
A database consists of a file or a set of files. The information in the these files may be broken down into records, each of which consists of one or more fields are the basic units of data storage, and each field typically contains information pertaining to one aspect or attribute of the entity described by the database. Using keywords and various mands, users can rapidly search, rearrange, group, and select the fields in many records to retrieve or create reports on particular aggregates of data.
Database records and files must anized to allow retrieval of the information. Early system were arranged sequentially (., alphabetically, numerically, or chronologically); the development of direct-access storage devices made possible random access to data via indexes. Queries are the main way users retrieve database information. Typically the user provides a string of characters, and puter searches the database for a corresponding sequence and provides the source materials in which those characters appear. A user can request, for example, all records in which the content of the field for a person’s last name is the word many users of a large database must be able to manipulate the information within it quickly at any given time. Moreover, large business and anizations tend to build up many independent files containing related and even overlapping data, and their data, processing activities often require the linking of data from several files. Several different types of database management systems have