The term database originated within the computing discipline. Although
its meaning has been broadened by popular use, even to include non-electronic
databases, this article is about computer databases.
A computer database is astructured collection of records or data that is stored
in a computer system so that a computer program or person using a
query language can consult it to answer queries href="http://en.wikipedia.org/wiki/Database#_note-0">[1].
The records retrieved in answer to queries are information that can be used to make decisions.
The computer program used to manage and query a database is known as a
database management system (DBMS). The properties and design of database
systems are included in the study of information science.
A typical query could be a question such as, How many hamburgers with two or
more beef patties were sold in the month of March in New Jersey?". To answer
such a question, the database would have to store information about hamburgers
sold, including number of patties, sales date, and the region.
The central concept of a database is that of a collection of records, or
pieces of information. Typically, for a given database, there is a structural
description of the type of facts held in that database: this description is
known as a schema. The schema describes the objects that are represented in the
database, and the relationships among them. There are a number of different ways
of organizing a schema, that is, of modeling the database structure: these are
known as database models(or data models). The model in most common use today is the
relational model, which in layman's terms represents all information in the
form of multiple related tables each consisting of rows and columns (the formal
definition uses mathematical terminology). This model represents relationships
by the use of values common to more than one table. Other models such as the
hierarchical model and the network model use a more explicit representation of relationships.
The term database refers to the collection of related records, and the
software should be referred to as the database management system or DBMS.
When the context is ambiguous, however, many database administrators and
programmers use the term database to cover both meanings.
Many professionals consider a collection of data to constitute a database
only if it has certain properties: for example, if the data is managed to ensure
its integrity and quality, if it allows shared access by a community of users,
if it has a schema, or if it supports a
query language. However, there is no definition of these properties that is
universally agreed upon.
Database management systems are usually categorized according to the data
model that they support: relational, object-relational, network, and so on. The
data model will tend to determine the query languages that are available to
access the database. A great deal of the internal engineering of a DBMS,
however, is independent of the data model, and is concerned with managing
factors such as performance, concurrency, integrity, and recovery from hardware
failures. In these areas there are large differences between products.
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