Matthew Simon Cavalletto


DBIx::SQLEngine::Docs::ReadMe - Welcome to DBIx::SQLEngine


The DBIx::SQLEngine class provides an extended interface for the DBI database framework. Each SQLEngine object is a wrapper around a DBI database handle, adding methods that support ad-hoc SQL generation and query execution in a single call. Dynamic subclassing based on database server type enables cross-platform portability.


DBIx::SQLEngine is the latest generation of a toolkit used by the authors for several years to develop business data applications and object-relational mapping toolkits. Its goal is to simplify dynamic query execution with the following capabilities:

  • Data-driven SQL: Ad-hoc generation of SQL statements from Perl data structures in a variety of formats; simple hash and array references are flexibly converted to form clauses in standard SQL query syntax.

  • High-Level Interface: Standard query operations are handled by a single method call each. Error handling is standardized, and routine annoyances like timed-out connections are retried automatically.

  • Full DBI Access: Accepts arbitrary SQL queries with placeholder parameters to be passed through, and delegates all other method calls to a wrapped database handle, allowing access to the entire DBI API for cases when high-level interfaces are insufficient

  • Portability Subclasses: Uses dynamic subclassing (via DBIx::AnyDBD) to allow platform-specific support for driver idiosyncrasies and DBMS workarounds. This release includes subclasses for connections to MySQL, PostgreSQL, Oracle, and Microsoft SQL servers, as well as for the standalone SQLite, AnyData, and CSV packages.

Data-driven SQL

Several methods are responsible for converting their arguments into commands and placeholder parameters in SQL, the Structured Query Language.

The various methods whose names being with sql_, like sql_select and sql_insert, each accept a hash of arguments and combines then to return a SQL statement and corresponding parameters. Data for each clause of the statement is accepted in multiple formats to facilitate query abstraction, often including various strings, array refs, and hash refs. Each method also supports passing arbitrary queries through using a sql parameter.

High-Level Interface

The combined query interface provides a useful high-level idiom to perform the typical cycle of SQL generation, query execution, and results fetching, all through a single method call.

The various fetch_*, visit_* and do_* methods that don't end in _sql, like fetch_select and do_insert, are wrappers that combine a SQL-generation and a SQL-execution method to provide a simple ways to perform a query in one call.

Full DBI Access

Each DBIx::SQLEngine object is implemented as a wrapper around a database handle provided by DBI, the Perl Database Interface.

Arbitrary queries can be executed, bypassing the SQL generation capabilities. The methods whose names end in _sql, like fetch_sql and do_sql, each accept a SQL statement and parameters, pass it to the DBI data source, and return information about the results of the query.

Portability Subclasses

Behind the scenes, different subclasses of SQLEngine are instantiated depending on the type of server to which you connect, thanks to DBIx::AnyData. As a result, some range of SQL dialect ideosyncracies can be compensated for.

For example, the sql_limit method controls the syntax for select statements with limit and offset clauses, and both MySQL and Oracle override this method to use their local syntax.

The only method that's actually provided by the DBIx::SQLEngine class itself is the new() constructor. All of the other methods are defined in DBIx::SQLEngine::Driver::Default, or in one of its automatically-loaded subclasses.

The public interface of DBIx::SQLEngine is shared by all of its subclasses. The superclass methods aim to produce and perform generic queries in an database-independent fashion, using standard SQL syntax. Subclasses may override these methods to compensate for idiosyncrasies of their database server or mechanism. To facilitate cross-platform subclassing, many of these methods are implemented by calling combinations of other methods, which may individually be overridden by subclasses.



This version is a routine release of DBIx::SQLEngine intended for public use.

This module's proposed CPAN registration should read:

  Name            DSLIP  Description
  --------------  -----  ---------------------------------------------
  ::SQLEngine     Rdpop  Extends DBI with high-level operations


This package requires these other modules and libraries:

  DBI                           1.0
  DBIx::AnyDBD                  2.0
  Class::MakeMethods            1.003

You must also have at least one working DBD module installed.

If you run into trouble, check that your DBI and DBD modules are up-to-date; in particular, if you are using DBD::CSV or DBD::AnyData, make sure you have upgraded to SQL::Statement 1.0 or later.


You should be able to install this module using the CPAN shell interface:

  perl -MCPAN -e 'install DBIx::SQLEngine'

In order for the test to succeed, you must also have at least one working DBD module installed, and must provide a DSN to which the script can connect with permissions to create tables.

Alternately, you may retrieve this package from CPAN or from the author's site:




After downloading the distribution, follow the normal procedure to unpack and install it, using the commands shown below or their local equivalents on your system:

  tar xzf DBIx-SQLEngine-*.tar.gz
  cd DBIx-SQLEngine-*
  perl Makefile.PL
  make test && sudo make install

Furthermore, thanks to the kind generosity of other members of the Perl community, this distribution is also available repackaged in the FreeBSD "ports" and Linux RPM formats. This may simplify installation for some users, but be aware that these alternate distributions may lag a few versions behind the latest release on CPAN.



Tested Platforms

This release has been tested succesfully on the following platforms:

  5.6.1 on darwin

You may also review the current test results from CPAN-Testers:



Known Problems

Many types of database servers are not yet supported.

Database driver/server combinations that do not support placeholders will fail. (

See DBIx::SQLEngine::ToDo for additional bugs and missing features.

Release Status

This module has been used in a variety of production systems and has been available on CPAN for over a year, with several other distributions dependant on it, so it would be fair to say that it is fully released.

However, while the commonly-used portions are well tested, some of the more obscure combinations of options are less so, and new bug reports do trickle in occasionally. If you do encounter any problems, please inform the author and I'll endeavor to patch them promptly.

Additional features have been outlined for future development, but the intent is support these by adding more options to the declaration interface, while maintaining backward compatibility.


If you have questions or feedback about this module, please feel free to contact the author at the below address. Although there is no formal support program, I do attempt to answer email promptly.

I would be particularly interested in any suggestions towards improving the documentation, correcting any Perl-version or platform dependencies, as well as general feedback and suggested additions.

Bug reports that contain a failing test case are greatly appreciated, and suggested patches will be promptly considered for inclusion in future releases.

To report bugs via the CPAN web tracking system, go to or send mail to, replacing the # with @.


If you've found this module useful or have feedback about your experience with it, consider sharing your opinion with other Perl users by posting your comment to CPAN's ratings system:


For more general discussion, you may wish to post a message on PerlMonks or the comp.lang.perl.misc newsgroup:



There have been a few small discussions of this module on PerlMonks and Usenet in the past:




See DBIx::SQLEngine for interface documentation.

See DBIx::SQLEngine::Docs::Changes for revision history.

See DBIx::SQLEngine::Docs::Related for notes on related modules.



Developed by Matthew Simon Cavalletto at Evolution Softworks.

You may contact the author directly at or More free Perl software is available at


Many thanks to the kind people who have contributed code and other feedback:

  Eric Schneider, Evolution Online Systems
  E. J. Evans, Evolution Online Systems
  Matthew Sheahan, Evolution Online Systems
  Eduardo Iturrate, Evolution Online Systems
  Ron Savage
  Christian Glahn, Innsbruck University
  Michael Kroll, Innsbruck University

Copyright 2001, 2002, 2003, 2004 Matthew Cavalletto.

Portions copyright 1998, 1999, 2000, 2001 Evolution Online Systems, Inc.

Portions copyright 2002 ZID, Innsbruck University (Austria).

Portions of the documentation are copyright 2003 Ron Savage.


You may use, modify, and distribute this software under the same terms as Perl.