SQL

In the early 1970s, the computer research team at IBM led by Edgar F. Codd undertook to realise concretely the relational model he had presented in 1970 in his foundational paper "A Relational Model of Data for Large Shared Data Banks." The relational model broke with prior approaches to data management — the hierarchical model and the network model — by proposing to organise data as tables composed of rows and columns, where each element could be queried using rigorous mathematical algebra. In 1974, Donald Chamberlin and Raymond Boyce, researchers at IBM in San Jose, developed the SEQUEL language (Structured English Query Language) designed to provide a more intuitive and natural interface to the relational model than pure mathematical notation. SEQUEL allowed a non-mathematician user to formulate complex queries on relational databases through phrases resembling structured English. The language incorporated the fundamental operators of relational algebra — projection, selection, join — while rendering them accessible and elegant. IBM created in 1975 the first functional prototype of the system, named System/R, deployed experimentally in universities and with IBM customers, whose practical success validated the concept with the wider industry. The language was renamed SQL (Structured Query Language) from 1977 onwards due to trademark issues. A first international standardisation occurred in 1986 when ANSI (American National Standards Institute) adopted the SQL standard, followed in 1987 by ISO (International Organization for Standardization). This drive toward standardisation accompanied the emergence of dozens of commercial and open-source relational database management systems: Informix, Sybase, PostgreSQL, MySQL and many others implemented SQL while enriching it with proprietary features. Since 1974, SQL has become the de facto query language for nearly all applications using a database, whether small (SQLite) or massive (Oracle, SQL Server). Beyond the specific domain of relational databases, SQL has influenced the design of later languages for querying and transforming structured data, from XQuery for XML to distributed computing with Spark SQL. Its combination of a natural-language-like syntax, mathematical power and rigorous standardisation made it the dominant paradigm for data access, fifty years after its design by Chamberlin and Boyce.