Query language is crucial to the construction and manipulation of the repositories of computerized data. The design of query languages allows the user to, in effect, ask a question of the data, and then to examine only a selected data point or larger portions of the data to attempt to answer the question. An important feature of query languages is the utility with multiple databases that have been constructed using the same platform. In the age of the Internet, with the multitude of databases, the ability to retrieve and compare data from a wide variety of sources is extremely useful and productive.

One of the most important of these database building blocks is the Structured Query Language, or SQL. It is used to navigate through the so-called relational databases, where data can be spread across multiple tables. It is a flexible query language, and so enjoys...