Oracle SQL: the Essential Reference

The Evolution of SQL: the 1990s and Beyond

If the 1970s was the decade of SQL invention, and the 1980s was the decade of SQL commercialization, then the 1990s was the decade of SQL evolution. During this period, the various vendors with SQL products raced to bring to market the features needed to support new and demanding applications. Commercial SQL products and the SQL standards have both been extended, in recent years, with new features to support object-oriented programming languages and multimedia data, integration with Java and XML, and the requirements of data warehouse applications. SQL is clearly a living language, with new capabilities developed in response to market demands.

In the early 1990s, the object-oriented programming paradigm became popular for commercial application development, because programmers found they could write complex applications more quickly and reliably using the object approach. An object-oriented language permits the programmer to define types (or classes) that describe not only the structure of data, but its behavior as well. Types can have complex structures and can include procedures (methods) as part of their definition. Types can be derived from other types, inheriting attributes from parent types. A fundamental concept of the object paradigm is that every object has a distinct identifier, and one object can refer directly to another via its object identifier.

Although it was not until the late 1990s that object technology had an influence ...