Programming the Perl DBI

Chapter 3. SQL and Relational Databases

The Structured Query Language, or SQL,^[19] is a language designed for the purpose of manipulating data within databases.

In 1970, E. F. Codd, working for IBM, published a now classic paper, “A Relational Model of Data for Large Shared Data Banks,” in which he laid down a set of abstract principles for data management that became known as the relational model. The entire field of relational database technology has its roots in that paper.

One of the many research projects sparked by that paper was the design and implementation of a language that could make interacting with relational databases simple. And it didn’t make the programmer write horrendously complex sections of code to interact with the database.^[20]

This chapter serves to give the complete database neophyte a very limited overview of what SQL is and how you can do some simple tasks with it. Many of the more complex details of SQL’s design and operation have been omitted or greatly simplified to allow the neophyte to learn enough to use the DBI in a simple, but effective, way. Section “Resources " in the Preface lists other books and web sites dedicated to SQL and relational database technologies.

^[19] Officially pronounced ``ess-que-ell,'' although ``sequel'' is also popular. We have also heard the term ``squeal,'' but that’s usually only heard when people first see the syntax or when they’ve just deleted all their data!

^[20] Chapter 2 shows many examples of how long-winded and inflexible ...