A Database is an integrated collection of logically related records or files that is stored in a computer system which consolidates records previously stored in separate files into a common pool of data records that provides data for many applications. A Database is a collection of information that is organized so that it can easily be accessed, managed, and updated according to the structure of an Information. In one view, databases can be classified according to types of content: bibliographic, full-text, numeric, and images. The structure is achieved by organizing the data according to a database model. The model that is most commonly used today is the relational model. Other models such as the hierarchical model and the network model use a more explicit representation of relationships.
Depending on the intended use, there are a number of database architectures in use. Many databases use a combination of strategies. On-line Transaction Processing systems (OLTP) often use a row-oriented datastore architecture, while data-warehouse and other retrieval-focused applications like Google's BigTable, or bibliographic database (library catalogue) systems may use a Column-oriented DBMS architecture.
Document-Oriented, XML, knowledgebases, as well as frame databases and RDF-stores (aka triple-stores), may also use a combination of these architectures in their implementation.
Finally, it should be noted that not all databases have or need a database schema (so called schema-less databases).
Over many years the database industry has been dominated by General Purpose database systems, which offer a wide range of functions that are applicable to many, if not most circumstances in modern data processing. These have been enhanced with extensible datatypes, pioneered in the PostgreSQL project, to allow a very wide range of applications to be developed. There are also other types of database which cannot be classified as relational databases.
A Database Management System (DBMS) is a set of computer programs that controls the creation, maintenance, and the use of the database of an organization and its end users. It allows organizations to place control of organizationwide database development in the hands of Database Administrators (DBAs) and other specialist. DBMSes may use any of a variety of database models, such as the network model or relational model. In large systems, a DBMS allows users and other software to store and retrieve data in a structured way.
A computer database relies on software to organize the storage of data. This software is known as a database management system (DBMS). Database management systems are categorized according to the database model that they support. The model tends 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.
A Relational Database Management System (RDBMS) implements the features of the relational model outlined above. In this context, Date's "Information Principle" states: "the entire information content of the database is represented in one and only one way. Namely as explicit values in column positions (attributes) and rows in relations (tuples). Therefore, there are no explicit pointers between related tables."
Operational Databases. These databases store detailed data needed to support the operations of the entire organization. They are also called Subject Area Databases (SADB), Transaction Databases, and Production Databases. These are all examples:
- Customer Databases
- Personal Databases
- Inventory Databases
Analytical Databases. These databases stores data and information extracted from selected operational and external databases. They consist of summarized data and information most needed by an organizations manager and other end user. They may also be called multidimensional database, Management database, and Information database.
Data Warehouse Databases. It stores data from current and previous years that has been extracted from the various operational databases of an organization. It is the central source of data that has been screened, edited, standardized and integrated so that it can be used by managers and other end user professionals throughout an organization
Distributed Databases. These are databases of local work groups and departments at regional offices, branch offices, manufacturing plants and other work sites. These databases can include segments of both common operational and common user databases, as well as data generated and used only at a user’s own site.
End-User Databases. These databases consist of a variety of data files developed by end-users at their workstations. Examples of these are collection of documents in spreadsheets, word processing and even downloaded files.
External Databases. These databases where access to external, privately owned online databases or data banks is available for a fee to end users and organizations from commercial services. Access to a wealth of information from external database is available for a fee from commercial online services and with or without charge from many sources in the internet.
Hypermedia Databases. These are set of interconnected multimedia pages at a web-site. It consists of home page and other hyperlinked pages of multimedia or mixed media such as text, graphic, photographic images, video clips, audio etc.
Navigational databases. Type of database characterized by the fact that objects in it are found primarily by following references from other objects. Traditionally navigational interfaces are procedural, though one could characterize some modern systems like XPath as being simultaneously navigational and declarative.
Database security denotes the system, processes, and procedures that protect a database from unintended activity.
Security is usually enforced through access control, auditing, and encryption.
- Access control ensures and restricts who can connect and what can be done to the database.
- Auditing logs what action or change has been performed, when and by whom.
- Encryption: Since security has become a major issue in recent years, many commercial database vendors provide built-in encryption mechanisms. Data is encoded natively into the tables and deciphered "on the fly" when a query comes in. Connections can also be secured and encrypted if required using DSA, MD5, SSL or legacy encryption standard.
Enforcing security is one of the major tasks of the DBA.
In the United Kingdom, legislation protecting the public from unauthorized disclosure of personal information held on databases falls under the Office of the Information Commissioner. United Kingdom based organizations holding personal data in electronic format (databases for example) are required to register with the Data Commissioner.
