Saturday, 17 August 2013

DB2 The Origins of SQL.

One of the more important successes attributed to this project is the development of SQL. But SQL’s roots are actually based in a research language called Specifying Queries As Relational Expressions (SQUARE). This language was developed in 1975 (predating the System R project) and was designed to implement relational algebra with English-style sentences.
Dr. E. F. Codd presented the relational database model to the world in 1970.
Soon after this landmark moment, organizations such as universities and research laboratories began efforts to develop a language that could be used as the foundation to a database system that supported the relational model. Initial work led to the development of several languages in the mid- to early 1970s, and later efforts resulted in the development of SQL and the SQL-based databases in use today. But just where did SQL originate? How did it evolve? What is its future? For the answers to these questions, we must begin our story at IBM’s Santa Teresa Research Laboratory in San Jose, California.
IBM began a major research project in the early 1970s called System/R. The goals of this project were to prove the viability of the relational model and to gain some experience in designing and implementing a relational database. The researchers’ initial endeavors between 1974 and 1975 proved successful, and they managed to produce a minimal prototype of a relational database.
In addition to their efforts to develop a working relational database, researchers were also working to define a database language. The work performed at this laboratory is arguably the most commercially significant of the initial efforts to define such a language. In 1974, Dr. Donald Chamberlin and his colleagues developed Structured English Query Language (SEQUEL). The language allowed users to query a relational database using clearly defined English-style sentences. Dr. Chamberlin and his staff first implemented this new language in a prototype database called SEQUEL-XRM.
The initial feedback and success of SEQUEL-XRM encouraged Dr. Chamberlin and his staff to continue their research. They completely revised SEQUEL between 1976 and 1977 and named the new version SEQUEL/2. However, they subsequently had to change the name SEQUEL to SQL (Structured Query Language or SQL Query Language) for legal reasons—someone else had already used the acronym SEQUEL. To this day, many people still pronounce SQL as sequel, although the widely accepted “official”pronunciation is es-cueel. SQL provided several new features, such as support for multi-table queries and shared data access by multiple users.
Soon after the emergence of SQL, IBM began a new and more ambitious project aimed at producing a prototype database that would further substantiate the feasibility of the relational model. They called the new prototype System R and based it on a large subset of SQL. After much of the initial development work was completed, IBM installed System R in a number of internal sites and selected client sites for testing and evaluation. Many changes were made to System R and SQL based on the experiences and feedback of users at these sites. IBM closed the project in 1979 and concluded that the relational model was indeed a viable database technology with commercial potential.

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