Data base
also called electronic database
any collection of data, or information,
that is specially organized for rapid search and retrieval by a computer.
Databases are structured to facilitate the storage, retrieval, modification,
and deletion of data in conjunction with various data-processing operations. A database management system (DBMS) extracts information
from the database in response to queries.
A brief treatment of databases follows. For full treatment, see
computer science: Information systems and databases; information processing.
A database is stored as a file or a
set of files on magnetic disk or tape, optical disk, or some other secondary
storage device. 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. Records are also organized into tables
that include information about relationships between its various fields.
Although database is applied loosely to any collection of information in
computer files, a database in the strict sense provides cross-referencing
capabilities. Using keywords and various sorting commands, 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 be organized to allow
retrieval of the information. Queries are the main way
users retrieve database information. The power of a DBMS comes from its ability
to define new relationships from the basic ones given by the tables and to use
them to get responses to queries. Typically, the user provides a string of
characters, and the computer 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 contents of the field for a
person's last name is the word Smith.
The many users of a large database must be able to
manipulate the information within it quickly at any given time. Moreover, large
business and other organizations 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 DBMS have been developed to support these requirements:
flat, hierarchical, network, relational, and object-oriented.
Early systems were arranged sequentially (i.e.,
alphabetically, numerically, or chronologically); the development of
direct-access storage devices made possible random access to data via indexes.
In flat databases, records are organized according to a
simple list of entities; many simple databases for personal computers are flat
in structure. The records in hierarchical databases are
organized in a treelike structure, with each level of records branching off
into a set of smaller categories. Unlike hierarchical databases, which provide
single links between sets of records at different levels, network
databases create multiple linkages between sets by placing links, or
pointers, to one set of records in another; the speed and versatility of
network databases have led to their wide use within businesses and in
e-commerce. Relational databases are used where
associations between files or records cannot be expressed by links; a simple
flat list becomes one row of a table, or “relation,” and multiple relations can
be mathematically associated to yield desired information. Various iterations
of SQL (Structured Query Language) are widely employed in DBMS for relational databases. Object-oriented databases
store and manipulate more complex data structures, called “objects,” which are
organized into hierarchical classes that may inherit properties from classes
higher in the chain; this database structure is the most flexible and
adaptable.
The information in many databases consists of
natural-language texts of documents; number-oriented databases primarily
contain information such as statistics, tables, financial data, and raw
scientific and technical data. Small databases can be maintained on
personal-computer systems and may be used by individuals at home. These and
larger databases have become increasingly important in business life, in part
because they are now commonly designed to be integrated with other office
software, including spreadsheet programs.
Typical commercial database applications include airline
reservations, production management functions, medical records in hospitals,
and legal records of insurance companies. The largest databases are usually maintained
by governmental agencies, business organizations, and universities. These
databases may contain texts of such materials as abstracts, reports, legal
statutes, wire services, newspapers and journals, encyclopaedias, and catalogs
of various kinds. Reference databases contain bibliographies or indexes that
serve as guides to the location of information in books, periodicals, and other
published literature. Thousands of these publicly accessible databases now
exist, covering topics ranging from law, medicine, and engineering to news and
current events, games, classified advertisements, and instructional courses.
Increasingly, formerly separate databases are being
combined electronically into larger collections known as data
warehouses. Businesses and government agencies then employ “data mining” software to analyze multiple aspects of the
data for various patterns. For example, a government agency might flag for
human investigation a company or individual that purchased a suspicious
quantity of certain equipment or materials, even though the purchases were
spread around the country or through various subsidiaries.
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