Database

Lore & Background

The concept of a database was made possible by the emergence of direct access storage media such as magnetic disks, which became widely available in the mid-1960s; earlier systems relied on sequential storage of data on magnetic tape. The Oxford English Dictionary cites a 1962 report by the System Development Corporation of California as the first to use the term "data-base" in a specific technical sense. The subsequent development of database technology can be divided into three eras based on data model or structure: navigational, SQL/relational, and post-relational. The two main early navigational data models were the hierarchical model and the CODASYL model (network model). These were characterized by the use of pointers to follow relationships from one record to another. The relational model, first proposed in 1970 by Edgar F. Codd, departed from this tradition by insisting that applications should search for data by content, rather than by following links. In the 2000s, non-relational databases became popular, collectively referred to as NoSQL, because they use different query languages. Object databases were developed in the 1980s to overcome the inconvenience of object–relational impedance mismatch, leading to hybrid object–relational databases. The next generation of post-relational databases in the late 2000s became known as NoSQL databases, introducing fast key–value stores and document-oriented databases.

Reader's Guide

Databases and their DBMSs are central to computing, enabling the organized storage and retrieval of data across applications. The relational model, dominant since the 1980s, uses tables with rows and columns and the SQL language, while NoSQL databases emerged in the 2000s with different query languages for specialized needs. The design of databases spans formal techniques and practical considerations, including data modeling, efficient data representation and storage, query languages, security and privacy of sensitive data, and distributed computing issues such as concurrent access and fault tolerance. The sizes, capabilities, and performance of databases and their respective DBMSs have grown in orders of magnitude, enabled by technology progress in processors, computer memory, computer storage, and computer networks. Database systems are categorized by the database model(s) they support, the type(s) of computer they run on, the query language(s) used, and their internal engineering, which affects performance, scalability, resilience, and security. The term "database" is often used casually to refer to both a database and the DBMS used to manipulate it, and outside professional IT, it may refer to any collection of related data such as a spreadsheet or card index.

Did You Know?

• The term "database" was first used in a 1962 report by the System Development Corporation of California.
• The relational model was first proposed in 1970 by Edgar F. Codd.
• The two main early navigational data models were the hierarchical model and the CODASYL (network) model.
• NoSQL databases became popular in the 2000s, using different query languages than SQL.