The history of SQL (pronounced English spelling in the letters that compose it, ie "this-cu-L" and not "siquel" as is often heard ) begins in 1974 with the definition, by Donald Chamberlin and others working in the IBM research labs, a language for specifying the characteristics of databases that adopted the relational model. This language called SEQUEL (Inglés Structured Query Language) and implemented in a prototype called SEQUEL-XRM between 1974 and 1975. Experiments with this prototype led, between 1976 and 1977, a revision of the language (SEQUEL / 2), which thereafter changed its name for legal reasons, becoming SQL . The prototype (System R), based on this language was adopted and used internally at IBM and adopted some of their chosen customers. With the success of this system, which was not yet sold, but other companies began to develop products based relational SQL. Since 1981, IBM began delivering its products and in 1983 relational began to sell DB2. During the eighties, many companies (eg Oracle and Sybase, to name a few) marketed products based on SQL, which becomes the de facto industry standard with respect to relational databases.
In 1986, adopted ANSI SQL (SQL dialect adopted substantially IBM) as a standard for relational languages \u200b\u200band in 1987 transfomer in ISO standard. This version of the standard goes by the name of SQL/86. In subsequent years, it has undergone several revisions have led SQL/89 first version and then the current SQL/92 .
Having defined a standard language for relational databases potentially opens the way to intercommunicability among all products based on it. From a practical standpoint, unfortunately things were otherwise. Indeed, in general, each manufacturer adopts and implements in-house database only the heart of the SQL language (the so-called Entry level or at most the Intermediate level), extending individually according to his own vision that everyone has the world's databases.
Currently, there is an ongoing review process of language by the ANSI committees and ISO, which should culminate in the definition of what now is known as SQL3 . The main features of this new incarnation of SQL should be its transformation into a stand-alone language (as language is now used as hosted in other languages) and the introduction of new complex data types that allow, for example, treatment of multimedia data.
Fernando A. More
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