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Collections of information records in digital form. A database will probably contain more than one type of record, with information on the linkages or relationships between different types, since the term \'file\' implies a simpler collection of only one type of record. To qualify as a database, there is often some degree of \'transparency\', a term implying that access to the records does not require detailed knowledge of how they are stored. Transparency is provided by a Database Management System (DBMS), which contains the necessary information on formats and coding schemes and handles requests expressed by the user in convenient terms.
Databases are used to store data and to respond to various kinds of requests from users. For example, an airline maintains a database containing its reservations, information on each of its flights, on its crews and employees, on its aircraft, and many more types of records. The database is accessed whenever information must be updated, and also whenever information is needed in response to a query, such as \'when does my flight arrive?\' Databases form one of the fundamental components of most geographic information systems (GIS), in which they are used to store records about the attributes and locations of the different kinds of features on the Earth\'s surface, and the connections that may exist between them. For example, a GIS database might store information on the street network of a city, including its links, intersections, directions of traffic, state of repair, traffic lights, levels of congestion etc.
Many DBMS have adopted the common query language SQL (Structured or Standard Query Language) which allows the user to formulate queries in a simple English-like syntax, and to switch freely from one manufacturer\'s DBMS to another without the need to learn a new command language. Some widely known DBMS include Oracle, INGRES, INFO, DBase, Access and FileMaker. The database approach is being used increasingly to handle, distribute and access the large collections of social and economic data maintained by national census and other agencies, and to make them available to researchers. (MG) |
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