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Structured query language, more widely recognized as SQL, is a special purpose programming language and a standard language for relational database management systems. SQL is effective in communicating with and managing data held in a relational database. A majority of database products available are based on SQL programming language, although customization of the standard language using proprietary extensions is common. Oracle, Sybase, Microsoft SQL Server, Access and many other leading databases use SQL.

SQL is primarily a declarative language, a non-imperative programming approach where appropriate results are identified as opposed to explicit commands that must be conducted. However, SQL does also include some procedural elements. SQL incorporates three different language varieties, data definition, data manipulation and data control all contribute to SQL outcomes.  

Donald D Chamberlin and Raymond F Boyce are credited with the development of SQL in the early 1970s. Experts in relational algebra and tuple relational calculus, the pair created the programming type to communicate with, retrieve and manipulate data from IBM's original database. They termed the language SEQUEL originally, referring to structured English query language, although a trademark conflict with a UK company saw it later changed to SQL.

Oracle, at the time named Relational Software, observed the concepts of Chamberlin and Boyce and saw a widespread application for the programming language. They developed their alternate version of SQL holding aspirations of securing business with US Government agencies. They began selling SQL RDBMS in June 1979.

The American National Standards Institute (ANSI) and International Organization for Standardisation (ISO) confirmed SQL as a standard in 1986 and 1987 respectively. Since then SQL has continued to evolve to include a larger set of features.

SQL programming language includes several language elements. Clauses are integral components of statements and queries. Expressions combine values operators and SQL functions. Predicates are used to limit the effect of statements and queries or change program flow. A query is an inquiry into the database using the SELECT statement. Statements control transactions, connections, sessions, perform diagnostics and more.

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