Perl in a Nutshell

Design of DBI

If DBM is too primitive for your database requirements, you’ll have to use a more sophisticated database package. Options include the commercial products Oracle, Sybase, and Informix, and the publically-available msql and mysql.

Prior to Perl Version 5 and DBI, the problem was that with all the database packages to choose from, there was no way to universalize database support for Perl. You’d have to rebuild the Perl executable itself against libraries that included subroutines for direct access to the database package. For example, sybperl and oraperl are both packages for building Perl Version 4 with Sybase and Oracle calls embedded, respectively. An application written for sybperl would not be portable to Oracle, or vice-versa. However, since current versions of Perl support binary extension loading at runtime, database support can now be added at runtime, which simplifies adding database interfaces to Perl programs while keeping the size of the Perl binary to a minimum.

Support for binary extensions doesn’t mean that database access has been standardized. There are still many database extensions to Perl, each with a different API. However, they all share a strikingly similar set of commands: connect to the database, issue queries, fetch results, and disconnect. This consistency has made it possible to develop a standard set of methods to work with any database. DBI defines a set of functions, variables, and conventions that provide a consistent database programming ...