Programming the Perl DBI

Chapter 2. Basic Non-DBI Databases

There are several ways in which databases organize the data contained within them. The most common of these is the relational database methodology. Databases that use a relational model are called Relational Database Management Systems , or RDBMSs. The most popular database systems nowadays (such as Oracle, Informix, and Sybase) are all relational in design.

But what does “relational” actually mean? A relational database is a database that is perceived by the user as a collection of tables, where a table is an unordered collection of rows. (Loosely speaking, a relation is a just a mathematical term for such a table.) Each row has a fixed number of fields, and each field can store a predefined type of data value, such as an integer, date, or string.

Another type of methodology that is growing in popularity is the object-oriented methodology, or OODBMS. With an object-oriented model, everything within the database is treated as an object of a certain class that has rules defined within itself for manipulating the data it encapsulates. This methodology closely follows that of object-oriented programming languages such as Smalltalk, C++, and Java. However, the DBI does not support any real OODBMS, so for the moment this methodology will not be discussed further.

Finally, there are several simplistic database packages that exist on various operating systems. These simple database packages generally do not feature the more sophisticated functionality ...