Chapter 7

For all that is great about the CGI module, it has its detractors. The usual com 

plaints fall along the lines of memory consumption, performance and sheer code 

size. For these reasons there are many competitors to CGI.pm on CPAN CGI::Lite,

7

CGI::Minimal,

8

 and CGI::Thin,

9

 to name a few. These modules tend to start by 

implementing just the core CGI functionality and grow slowly from there as the 

author realizes that this or that CGI.pm function is really quite useful after all. Ulti 

mately they may perform better and use less memory, but CGI.pm remains more 

popular for a good reason it does everything a CGI programmer needs and it 

does it well.

DBI

The DBI module, by Tim Bunce, provides Perl with an object oriented interface to 

virtually every relational database system under the sun (MySQL, PostgreSQL, 

Oracle, Sybase, and many more). DBI accomplishes this Olympian feat by relying 

on database driver (DBD) modules to interface with individual databases. For 

example, when you use DBI to talk to a PostgreSQL database, DBI loads the 

DBD::Pg

10

 module. If you want to connect to MySQL, the DBD::mysql

11

 module is 

loaded. Even CSV

12

 files can be accessed through the DBD::CSV

13

 module. There 

are DBD modules available for all of the commonly used databases, and many of 

the less common ones too.

Before DBI, uneven database connection libraries were the norm each 

database had its own modules and they all worked (or didn't work) differently. Perl 

was struggling to be useful for serious database software development. DBI provided a 

great platform for database interface libraries, and turned Perl into a serious 

database application programming environment.

DBI defines two interfaces a front end interface for users and a back end 

interface for DBD module programmers. Regardless of the underlying DBD 

module being used, the DBI front end interface remains the same. The benefit of 

this system is that users can learn to use the DBI module and employ those skills to 

access any database with a DBD driver. Also, code written to the DBI interface can 

be easily ported between databases.

14

7. Written by Benjamin Low

8. Written by Benjamin Franz

9. Written by R. Geoffrey Avery

10. Written by Jeffrey Baker

11. Written by Jochen Wiedmann

12. Stands for Comma Separated Values, a text format commonly used to store tabular data

13. Written by Jeff Zucker

14. This would be much easier if databases all spoke the same dialect of SQL, but unfortunately 

that is not the case.

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