Advanced Perl Programming

Relational Databases

Relational databases have been around for a while, and while most commercial implementations have standardized on SQL, they differ significantly in the native C API. There have been several solutions to this. Microsoft popularized the ODBC (Open DataBase Connectivity) initiative, which has become the de facto standard in the (Wintel) PC world and provides a standard frontend to a large number of relational databases. PC Perl users using the ActiveWare port can access the ODBC library using the Win32::ODBC module.

Meanwhile in the Perl/Unix world, Tim Bunce and other developers, who had been writing mutually incompatible wrapper modules for different databases, came up with the DBI (Database Interface) specification and implementation to merge their efforts. DBI is similar in spirit and interface to the ODBC specification.

The ODBC specification has recently been accepted as the basis for the SQL CLI (Call-Level Interface) ISO standard, and it is expected that all database vendors will eventually provide a compliant-client library. When that becomes common-place, you can expect the DBI implementation to be rewritten to take advantage of this interface or go away completely.

In this section, we will take a look at both DBI and Win32::ODBC.

DBI (Database Interface)

Back in the days when modules and dynamic loading were not built into Perl, the database wrappers had to be linked in to create custom Perl executables called sybperl (for Sybase), oraperl (for Oracle), ...