文档介绍：Database Management Systems( 3th Edition ),Wiley ,2004, 5-12
A introduction to Database Management System
Raghu Ramakrishnan
A database (sometimes spelled data base) is also called an electronic database , referring to any collection 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 .Databases 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 these files may be broken down into records, each of which consists of one or more fields. 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 aggregate of data.
Complex data relationships and linkages may be found in all but the simplest databases .The system software package that handles the difficult tasks associated with creating ,accessing, and maintaining database records is called a database management system(DBMS).The programs in a DBMS package establish an interface