The rest of the chapter focuses on SQL. A full coverage of SQL would require a large book itself, so many advanced features of the language are omitted. The treatment assumes familiarity with relational schemas and the main operations of relational algebra, as discussed earlier. This section provides a brief history and structural overview of SQL.

After the publication of Dr. Codd s classic paper on the relational model of data (Codd 1970), some early prototypes were developed to provide a relational DBMS, including a language for querying and updating relational databases. In 1974, Don Chamberlin and Raymond Boyce published a paper on a language called SEQUEL (Structured English Query Language) being implemented by a team at the IBM San Jose Research Laboratory as an interface to its System R relational prototype, within a project also called System R. By 1977, a revised version of this language (SEQUEL/2) had been defined and largely implemented by IBM. In the late 1970s it was discovered that Sequel was an existing trademark, so the language was renamed SQL . Although SQL is often pronounced Sequel , officially it is pronounced simply ess-cue-ell .

The System R project ran from 1971 through 1979, and later evolved into a distributed database project (System R*). Using the experience gained from its System R project, IBM built its first commercial relational DBMS, known as SQL/DS, which it released in 1981. Its second and highly influential SQL product, known as DB2, was released in 1983. As the...