Structured Query Language - IBM Mainframe

The name SQL pronounced as 'ess-cue-ell' or 'sequel is the abbreviation for Structured Query Language. The SQL consists of a set of facilities for defining, accessing and managing relational databases. In order to understand why SQL has become so popular and important, it is helpful to have an idea of the major developments in database technology over the past 20 to 30 years. Some of these are already covered in the earlier chapters, but we are repeating them again not to lose the flow of events.

  • In 1970 E.F Codd, member of IBM Lab in San Jose, California, published the classic paper, A Relational Model of Data for Large Shared Data Banks, in which he laid down a set of abstract principles of Database Management, the so called relational model. The entire field of relational database management system has its origins in that paper.
  • The Codd's paper triggered of a great deal of research and experimentation and led to the design and prototype implementation of a variety of relational languages. A relational language is a language that realizes, in some concrete syntactic form, some or all of the features of the abstract relational model. Several such languages were created in the early and mid 70s. One such language was Structured English Query Language (SEQUEL), defined by Donald Chambedin and others at the IBM San Jose Lab in 1974, and was implemented in the IBM prototype called SEQLEL-XRM in 1974-75.
  • As a result of the experience with SEQUEL-XRM, a revised and refined version of SEQUEL was released in 1976-77 called SEQUEL/2. This name was later changed to SQL. Based on the SEQUEL/2 or SQL another prototype was developed by IBM called System R. System R, an implementation of a large subset of the SQL, became operational in 1977 and was installed in a number of user sites. Based on user, feedback, the System R and the SQL underwent a lot of changes.
  • Getting inspiration from the success of system R, software companies other than IBM also began developing products that implemented SQL, and the first product that came out was ORACLE from Relational Software Inc. (now Oracle Corporation). In 1981, IBM announced its SQL product, SQL/DS, for the VSE environment, which was followed by a VM version in 1982. In 1983 IBM announced another product for the MVS environment called DB2, which was compatible with the SQL/DS.
  • Over the next several years, numerous other vendors announced their products. Some of them are DG/SQL from Data General Corporation (1984), SYBASE from Sybase Inc. (1986). In addition to this SQL interfaces were developed for existing products such as INGRESS and IDM. Now there are more than 100 products that support some dialect of SQL running on machines ranging from small PCs to the largest mainframes. SQL has become the de facto standard in the Relational Database world.
  • In 1982 the American Nation Standards Institute (ANSI) charted its database committee to develop a proposal for a standard relational language. The proposal of the committee was ratified by ANSI in 1986 and was accepted as the international standard in 1987 by the International Organization for Standardization (ISO). From then onwards the SQL standard has undergone various transformations and modifications over the years, and now the latest version is known as SQL2 or SQL/92 which was introduced in 1992.

Now that we have seen the history of the SQL, we will look briefly into some of the major facilities offered by standard SQL. The primary function of the SQL is to support the definition, manipulation and control of data in relational databases. A relational database as defined earlier, is a collection of tables, where a table is an un ordered collection of rows. SQL statements can be invoked either interactively in a terminal session or by embedding them in application programs.

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