SQL is a standard language for storing, manipulating and retrieving data in relational databases.
Introduction
Impedance mismatch is a term commonly used to describe the problem of an object-oriented (OO) application housing its data in legacy relational databases (RDBMS). C++ programmers have dealt with it for years, and it is now a familiar problem to Java and other OO programmers.
Impedance mismatch arises from the inherent lack of affinity between the object and relational models.
Introduction
With the maturation and wide acceptance of Java, object-oriented programming has moved to the foreground of the application development landscape. Because of their rich data models and support for productivity-enhancing concepts such as encapsulation, inheritance, and polymorphism, object technologies like Java, C++, and COM, are favored by today's application developers.
However, much of the world's data still resides in relational databases.