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DBI::FAQ(3pm)         User Contributed Perl Documentation        DBI::FAQ(3pm)



NAME
       DBI::FAQ -- The Frequently Asked Questions for the Perl5 Database
       Interface

SYNOPSIS
           perldoc DBI::FAQ

VERSION
       This document is currently at version 0.38, as of February 8th, 2000.

       That's very old. A newer FAQ can be found at
       <http://faq.dbi-support.com/>;

DESCRIPTION
       This document serves to answer the most frequently asked questions on
       both the DBI Mailing Lists and personally to members of the DBI
       development team.

Basic Information &&amp; Information Sources
       1.1 What is DBI, DBperl, Oraperl and *perl?

       To quote Tim Bunce, the architect and author of DBI:

           ``DBI is a database access Application Programming Interface (API)
             for the Perl Language. The DBI API Specification defines a set
             of functions, variables and conventions that provide a consistent
             database interface independant of the actual database being used.''

       In simple language, the DBI interface allows users to access multiple
       database types transparently. So, if you connecting to an Oracle,
       Informix, mSQL, Sybase or whatever database, you don't need to know the
       underlying mechanics of the 3GL layer. The API defined by DBI will work
       on all these database types.

       A similar benefit is gained by the ability to connect to two different
       databases of different vendor within the one perl script, ie, I want to
       read data from an Oracle database and insert it back into an Informix
       database all within one program. The DBI layer allows you to do this
       simply and powerfully.

       DBperl is the old name for the interface specification. It's usually
       now used to denote perl4 modules on database interfacing, such as,
       oraperl, isqlperl, ingperl and so on. These interfaces didn't have a
       standard API and are generally not supported.

       Here's a list of DBperl modules, their corresponding DBI counterparts
       and support information. Please note, the author's listed here
       generally do not maintain the DBI module for the same database. These
       email addresses are unverified and should only be used for queries
       concerning the perl4 modules listed below. DBI driver queries should be
       directed to the dbi-users mailing list.

           Module Name Database Required   Author          DBI
           ----------- -----------------   ------          ---
           Sybperl     Sybase              Michael Peppler DBD::Sybase
                                           <mpepplerATitf.ch>
           Oraperl     Oracle 6 & 7        Kevin Stock     DBD::Oracle
                                           <dbi-usersATperl.org>
           Ingperl     Ingres              Tim Bunce &     DBD::Ingres
                                           Ted Lemon
                                           <dbi-usersATperl.org>
           Interperl   Interbase           Buzz Moschetti  DBD::Interbase
                                           <buzzATbear.com>
           Uniperl     Unify 5.0           Rick Wargo      None
                                           <rickersATcoe.edu>
           Pgperl      Postgres            Igor Metz       DBD::Pg
                                           <metzATiam.ch>
           Btreeperl   NDBM                John Conover    SDBM?
                                           <johnATjohncon.com>
           Ctreeperl   C-Tree              John Conover    None
                                           <johnATjohncon.com>
           Cisamperl   Informix C-ISAM     Mathias Koerber None
                                           <mathiasATunicorn.sg>
           Duaperl     X.500 Directory     Eric Douglas    None
                       User Agent

       However, some DBI modules have DBperl emulation layers, so, DBD::Oracle
       comes with an Oraperl emulation layer, which allows you to run legacy
       oraperl scripts without modification. The emulation layer translates
       the oraperl API calls into DBI calls and executes them through the DBI
       switch.

       Here's a table of emulation layer information:

           Module                  Emulation Layer     Status
           ------          ---------------     ------
           DBD::Oracle     Oraperl             Complete
           DBD::Informix   Isqlperl            Under development
           DBD::Ingres     Ingperl             Complete?
           DBD::Sybase     Sybperl             Working? ( Needs verification )
           DBD::mSQL       Msqlperl            Experimentally released with
                                               DBD::mSQL-0.61

       The Msqlperl emulation is a special case. Msqlperl is a perl5 driver
       for mSQL databases, but does not conform to the DBI Specification. It's
       use is being deprecated in favour of DBD::mSQL. Msqlperl may be
       downloaded from CPAN via:

           http://www.perl.com/cgi-bin/cpan_mod?module=Msqlperl

       1.2. Where can I get it from?

       The Comprehensive Perl Archive Network resources should be used for
       retrieving up-to-date versions of the DBI and drivers. CPAN may be
       accessed via Tom Christiansen's splendid CPAN multiplexer program
       located at:

           http://www.perl.com/CPAN/

       For more specific version information and exact URLs of drivers, please
       see the DBI drivers list and the DBI module pages which can be found
       on:

           http://dbi.perl.org/
           http://www.symbolstone.org/technology/perl/DBI

       This list is automatically generated on a nightly basis from CPAN and
       should be up-to-date.

       1.3. Where can I get more information?

       There are a few information sources on DBI.

       "Programming the Perl DBI"
           "Programming the Perl DBI" is the official book on the DBI written
           by Alligator Descartes and Tim Bunce and published by O'Reilly &
           Associates.  The book was released on February 9th, 2000.

           The table of contents is:

               Preface
               1. Introduction
                   From Mainframes to Workstations
                   Perl
                   DBI in the Real World
                   A Historical Interlude and Standing Stones
               2. Basic Non-DBI Databases
                   Storage Managers and Layers
                   Query Languages and Data Functions
                   Standing Stones and the Sample Database
                   Flat-File Databases
                   Putting Complex Data into Flat Files
                   Concurrent Database Access and Locking
                   DBM Files and the Berkeley Database Manager
                   The MLDBM Module
                   Summary
               3. SQL and Relational Databases
                   The Relational Database Methodology
                   Datatypes and NULL Values
                   Querying Data
                   Modifying Data Within Tables
                   Creating and Destroying Tables
               4. Programming with the DBI
                   DBI Architecture
                   Handles
                   Data Source Names
                   Connection and Disconnection
                   Error Handling
                   Utility Methods and Functions
               5. Interacting with the Database
                   Issuing Simple Queries
                   Executing Non-SELECT Statements
                   Binding Parameters to Statements
                   Binding Output Columns
                   do() Versus prepare()
                   Atomic and Batch Fetching
               6. Advanced DBI
                   Handle Attributes and Metadata
                   Handling LONG/LOB Data
                   Transactions, Locking, and Isolation
               7. ODBC and the DBI
                   ODBC -- Embraced and Extended
                   DBI -- Thrashed and Mutated
                   The Nuts and Bolts of ODBC
                   ODBC from Perl
                   The Marriage of DBI and ODBC
                   Questions and Choices
                   Moving Between Win32::ODBC and the DBI
                   And What About ADO?
               8. DBI Shell and Database Proxying
                   dbish -- The DBI Shell
                   Database Proxying
               A. DBI Specification
               B. Driver and Database Characteristics
               C. ASLaN Sacred Site Charter
               Index

           The book should be available from all good bookshops and can be
           ordered online either <I>via</I> O'Reilly & Associates

               http://www.oreilly.com/catalog/perldbi

           or Amazon

               http://www.amazon.com/exec/obidos/ASIN/1565926994/dbi

       POD documentation
           PODs are chunks of documentation usually embedded within perl
           programs that document the code ``in place'', providing a useful
           resource for programmers and users of modules. POD for DBI and
           drivers is beginning to become more commonplace, and documentation
           for these modules can be read with the "perldoc" program included
           with Perl.

           The DBI Specification
               The POD for the DBI Specification can be read with the:

                   perldoc DBI

               command. The Specification also forms Appendix A of
               "Programming the Perl DBI".

           Oraperl
               Users of the Oraperl emulation layer bundled with DBD::Oracle,
               may read up on how to program with the Oraperl interface by
               typing:

                   perldoc Oraperl

               This will produce an updated copy of the original oraperl man
               page written by Kevin Stock for perl4. The oraperl API is fully
               listed and described there.

           Drivers
               Users of the DBD modules may read about some of the private
               functions and quirks of that driver by typing:

                   perldoc <driver>

               For example, the DBD::mSQL driver is bundled with driver-
               specific documentation that can be accessed by typing

                   perldoc DBD::mSQL

           Frequently Asked Questions
               This document, the Frequently Asked Questions is also available
               as POD documentation! You can read this on your own system by
               typing:

                   perldoc DBI::FAQ

               This may be more convenient to persons not permanently, or
               conveniently, connected to the Internet. The DBI::FAQ module
               should be downloaded and installed for the more up-to-date
               version.

               The version of DBI::FAQ shipped with the "DBI" module may be
               slightly out of date.

           POD in general
               Information on writing POD, and on the philosophy of POD in
               general, can be read by typing:

                   perldoc perlpod

               Users with the Tk module installed may be interested to learn
               there is a Tk-based POD reader available called "tkpod", which
               formats POD in a convenient and readable way. This is available
               via CPAN as the module called Tk::POD and is highly
               recommended.

       Driver and Database Characteristics
           The driver summaries that were produced for Appendix B of
           "Programming the Perl DBI" are available online at:

               http://dbi.perl.org/
               http://www.symbolstone.org/technology/perl/DBI

           in the driver information table. These summaries contain
           standardised information on each driver and database which should
           aid you in selecting a database to use. It will also inform you
           quickly of any issues within drivers or whether a driver is not
           fully compliant with the DBI Specification.

       Rambles, Tidbits and Observations
               http://dbi.perl.org/tidbits
               http://www.symbolstone.org/technology/perl/DBI/tidbits

           There are a series of occasional rambles from various people on the
           DBI mailing lists who, in an attempt to clear up a simple point,
           end up drafting fairly comprehensive documents. These are quite
           often varying in quality, but do provide some insights into the
           workings of the interfaces.

       Articles
           A list of articles discussing the DBI can be found on the DBI WWW
           page at:

               http://dbi.perl.org/
               http://www.symbolstone.org/technology/perl/DBI

           These articles are of varying quality and age, from the original
           Perl Journal article written by Alligator and Tim, to more recent
           debacles published online from about.com.

       README files
           The README files included with each driver occasionally contains
           some useful information ( no, really! ) that may be pertinent to
           the user.  Please read them. It makes our worthless existences more
           bearable. These can all be read from the main DBI WWW page at:

               http://dbi.perl.org/
               http://www.symbolstone.org/technology/perl/DBI

       Mailing Lists
           There are three mailing lists for DBI:

               dbi-announceATperl.org     -- for announcements, very low traffic
               dbi-usersATperl.org        -- general user support
               dbi-devATperl.org          -- for driver developers (no user support)

           For information on how to subscribe, set digest mode etc, and
           unsubscribe, send an email message (the content will be ignored)
           to:

               dbi-announce-helpATperl.org
               dbi-users-helpATperl.org
               dbi-dev-helpATperl.org

       Mailing List Archives
           US Mailing List Archives
                   http://outside.organic.com/mail-archives/dbi-users/

               Searchable hypermail archives of the three mailing lists, and
               some of the much older traffic have been set up for users to
               browse.

           European Mailing List Archives
                   http://www.rosat.mpe-garching.mpg.de/mailing-lists/PerlDB-Interest

               As per the US archive above.

Compilation Problems
       2.1. Compilation problems or "It fails the test!"

       First off, consult the README for that driver in case there is useful
       information about the problem. It may be a known problem for your given
       architecture and operating system or database. You can check the README
       files for each driver in advance online at:

           http://dbi.perl.org/
           http://www.symbolstone.org/technology/perl/DBI

       If it's a known problem, you'll probably have to wait till it gets
       fixed. If you're really needing it fixed, try the following:

       Attempt to fix it yourself
           This technique is generally not recommended to the faint-hearted.
           If you do think you have managed to fix it, then, send a patch file
           ( context diff ) to the author with an explanation of:

           o   What the problem was, and test cases, if possible.

           o   What you needed to do to fix it. Please make sure you mention
               everything.

           o   Platform information, database version, perl version, module
               version and DBI version.

       Email the author Do NOT whinge!
           Please email the address listed in the WWW pages for whichever
           driver you are having problems with. Do not directly email the
           author at a known address unless it corresponds with the one
           listed.

           We tend to have real jobs to do, and we do read the mailing lists
           for problems. Besides, we may not have access to <insert your
           favourite brain-damaged platform here> and couldn't be of any
           assistance anyway! Apologies for sounding harsh, but that's the way
           of it!

           However, you might catch one of these creative genii at 3am when
           we're doing this sort of stuff anyway, and get a patch within 5
           minutes. The atmosphere in the DBI circle is that we do appreciate
           the users' problems, since we work in similar environments.

           If you are planning to email the author, please furnish as much
           information as possible, ie:

           o   ALL the information asked for in the README file in the
               problematic module. And we mean ALL of it. We don't put lines
               like that in documentation for the good of our health, or to
               meet obscure README file standards of length.

           o   If you have a core dump, try the Devel::CoreStack module for
               generating a stack trace from the core dump. Send us that too.
               Devel::CoreStack can be found on CPAN at:

                   http://www.perl.com/cgi-bin/cpan_mod?module=Devel::CoreStack

           o   Module versions, perl version, test cases, operating system
               versions and any other pertinent information.

           Remember, the more information you send us, the quicker we can
           track problems down. If you send us no useful information, expect
           nothing back.

           Finally, please be aware that some authors, including Tim Bunce,
           specifically request that you do not mail them directly. Please
           respect their wishes and use the email addresses listed in the
           appropriate module "README" file.

       Email the dbi-users Mailing List
           It's usually a fairly intelligent idea to cc the mailing list
           anyway with problems. The authors all read the lists, so you lose
           nothing by mailing there.

Platform and Driver Issues
       3.1 What's the difference between ODBC and DBI?

       In terms of architecture - not much: Both define programming
       interfaces. Both allow multiple drivers to be loaded to do the actual
       work.

       In terms of ease of use - much: The DBI is a 'high level' interface
       that, like Perl itself, strives to make the simple things easy while
       still making the hard things possible. The ODBC is a 'low level'
       interface. All nuts-bolts-knobs-and-dials.

       Now there's an ODBC driver for the DBI (DBD::ODBC) the "What's the
       difference" question is more usefully rephrased as:

       Chapter 7 of "Programming the Perl DBI" covers this topic in far more
       detail and should be consulted.

       3.2 What's the difference between Win32::ODBC and DBD::ODBC?

       The DBI, and thus DBD::ODBC, has a different philosophy from the
       Win32::ODBC module:

       The Win32::ODBC module is a 'thin' layer over the low-level ODBC API.
       The DBI defines a simpler 'higher level' interface.

       The Win32::ODBC module gives you access to more of the ODBC API.  The
       DBI and DBD::ODBC give you access to only the essentials.  (But, unlike
       Win32::ODBC, the DBI and DBD::ODBC do support parameter binding and
       multiple prepared statements which reduces the load on the database
       server and can dramatically increase performance.)

       The Win32::ODBC module only works on Win32 systems.  The DBI and
       DBD::ODBC are very portable and work on Win32 and Unix.

       The DBI and DBD::ODBC modules are supplied as a standard part of the
       Perl 5.004 binary distribution for Win32 (they don't work with the
       older, non-standard, ActiveState port).

       Scripts written with the DBI and DBD::ODBC are faster than Win32::ODBC
       on Win32 and are trivially portable to other supported database types.

       The DBI offers optional automatic printing or die()ing on errors which
       makes applications simpler and more robust.

       The current DBD::ODBC driver version 0.16 is new and not yet fully
       stable.  A new release is due soon [relative to the date of the next
       TPJ issue :-] and will be much improved and offer more ODBC
       functionality.

       To summarise: The Win32::ODBC module is your best choice if you need
       access to more of the ODBC API than the DBI gives you. Otherwise, the
       DBI and DBD::ODBC combination may be your best bet.

       Chapter 7 of "Programming the Perl DBI" covers this topic in far more
       detail and should be consulted.

       3.3 Is DBI supported under Windows 95 / NT platforms?

       Finally, yes! Jeff Urlwin has been working diligently on building DBI
       and DBD::ODBC under these platforms, and, with the advent of a stabler
       perl and a port of MakeMaker, the project has come on by great leaps
       and bounds.

       The DBI and DBD::Oracle Win32 ports are now a standard part of DBI, so,
       downloading DBI of version higher than 0.81 should work fine as should
       using the most recent DBD::Oracle version.

       3.4 Can I access Microsoft Access or SQL-Server databases with DBI?

       Yes, use the DBD::ODBC driver.

       3.5 Is the a DBD for <&lt;insert favourite database here>&gt;?

       Is is listed on the DBI drivers page?

           http://dbi.perl.org/
           http://www.symbolstone.org/technology/perl/DBI

       If not, no. A complete absence of a given database driver from that
       page means that no-one has announced any intention to work on it, not
       that such a driver is impossible to write.

       A corollary of the above statement implies that if you see an
       announcement for a driver not on the above page, there's a good chance
       it's not actually a DBI driver, and may not conform to the
       specifications. Therefore, questions concerning problems with that code
       should not really be addressed to the DBI Mailing Lists.

       3.6 What's DBM? And why should I use DBI instead?

       Extracted from ``DBI - The Database Interface for Perl 5'':

           ``UNIX was originally blessed with simple file-based ``databases'', namely
           the dbm system. dbm lets you store data in files, and retrieve
           that data quickly. However, it also has serious drawbacks.

               File Locking

               The dbm systems did not allow particularly robust file locking
               capabilities, nor any capability for correcting problems arising through
               simultaneous writes [ to the database ].

               Arbitrary Data Structures

               The dbm systems only allows a single fixed data structure:
               key-value pairs. That value could be a complex object, such as a
               [ C ] struct, but the key had to be unique. This was a large
               limitation on the usefulness of dbm systems.

           However, dbm systems still provide a useful function for users with
           simple datasets and limited resources, since they are fast, robust and
           extremely well-tested. Perl modules to access dbm systems have now
           been integrated into the core Perl distribution via the
           AnyDBM_File module.''

       To sum up, DBM is a perfectly satisfactory solution for essentially
       read-only databases, or small and simple datasets. However, for more
       scaleable dataset handling, not to mention robust transactional
       locking, users are recommended to use a more powerful database engine
       via DBI.

       Chapter 2 of "Programming the Perl DBI" discusses DBM files in detail.

       3.7 What database do you recommend me using?

       This is a particularly thorny area in which an objective answer is
       difficult to come by, since each dataset, proposed usage and system
       configuration differs from person to person.

       From the current author's point of view, if the dataset is relatively
       small, being tables of less than 1 million rows, and less than 1000
       tables in a given database, then mSQL is a perfectly acceptable
       solution to your problem. This database is extremely cheap, is
       wonderfully robust and has excellent support. More information is
       available on the Hughes Technology WWW site at:

           http://www.hughes.com.au

       You may also wish to look at MySQL which is a more powerful database
       engine that has a similar feel to mSQL.

           http://www.tcx.se

       If the dataset is larger than 1 million row tables or 1000 tables, or
       if you have either more money, or larger machines, I would recommend
       Oracle RDBMS.  Oracle's WWW site is an excellent source of more
       information.

           http://www.oracle.com

       Informix is another high-end RDBMS that is worth considering. There are
       several differences between Oracle and Informix which are too complex
       for this document to detail. Information on Informix can be found on
       their WWW site at:

           http://www.informix.com

       In the case of WWW fronted applications, mSQL may be a better option
       due to slow connection times between a CGI script and the Oracle RDBMS
       and also the amount of resource each Oracle connection will consume.
       mSQL is lighter resource-wise and faster.

       These views are not necessarily representative of anyone else's
       opinions, and do not reflect any corporate sponsorship or views. They
       are provided as-is.

       3.8 Is <&lt;insert feature here>&gt; supported in DBI?

       Given that we're making the assumption that the feature you have
       requested is a non-standard database-specific feature, then the answer
       will be no.

       DBI reflects a generic API that will work for most databases, and has
       no database-specific functionality.

       However, driver authors may, if they so desire, include hooks to
       database-specific functionality through the "func()" method defined in
       the DBI API.  Script developers should note that use of functionality
       provided via the "func()" methods is very unlikely to be portable
       across databases.

Programming Questions
       4.1 Is DBI any use for CGI programming?

       In a word, yes! DBI is hugely useful for CGI programming! In fact, I
       would tentatively say that CGI programming is one of two top uses for
       DBI.

       DBI confers the ability to CGI programmers to power WWW-fronted
       databases to their users, which provides users with vast quantities of
       ordered data to play with. DBI also provides the possibility that, if a
       site is receiving far too much traffic than their database server can
       cope with, they can upgrade the database server behind the scenes with
       no alterations to the CGI scripts.

       4.2 How do I get faster connection times with DBD::Oracle and CGI?

           Contributed by John D. Groenveld

       The Apache "httpd" maintains a pool of "httpd" children to service
       client requests.

       Using the Apache mod_perl module by Doug MacEachern, the perl
       interpreter is embedded with the "httpd" children. The CGI, DBI, and
       your other favorite modules can be loaded at the startup of each child.
       These modules will not be reloaded unless changed on disk.

       For more information on Apache, see the Apache Project's WWW site:

           http://www.apache.org

       The mod_perl module can be downloaded from CPAN via:

           http://www.perl.com/cgi-bin/cpan_mod?module=Apache

       4.3 How do I get persistent connections with DBI and CGI?

           Contributed by John D. Groenveld

       Using Edmund Mergl's Apache::DBI module, database logins are stored in
       a hash with each of these "httpd" child. If your application is based
       on a single database user, this connection can be started with each
       child.  Currently, database connections cannot be shared between
       "httpd" children.

       Apache::DBI can be downloaded from CPAN via:

           http://www.perl.com/cgi-bin/cpan_mod?module=Apache::DBI

       4.4 ``When I run a perl script from the command line, it works, but,
       when I run it under the "httpd", it fails!'' Why?

       Basically, a good chance this is occurring is due to the fact that the
       user that you ran it from the command line as has a correctly
       configured set of environment variables, in the case of DBD::Oracle,
       variables like "ORACLE_HOME", "ORACLE_SID" or "TWO_TASK".

       The "httpd" process usually runs under the user id of "nobody", which
       implies there is no configured environment. Any scripts attempting to
       execute in this situation will correctly fail.

       One way to solve this problem is to set the environment for your
       database in a "BEGIN { }" block at the top of your script. Another
       technique is to configure your WWW server to pass-through certain
       environment variables to your CGI scripts.

       Similarly, you should check your "httpd" error logfile for any clues,
       as well as the ``Idiot's Guide To Solving Perl / CGI Problems'' and
       ``Perl CGI Programming FAQ'' for further information. It is unlikely
       the problem is DBI-related.

       The ``Idiot's Guide To Solving Perl / CGI Problems'' can be located at:

           http://www.perl.com/perl/faq/index.html

       as can the ``Perl CGI Programming FAQ''. Read BOTH these documents
       carefully!

       4.5 How do I get the number of rows returned from a "SELECT" statement?

       Count them. Read the DBI docs for the "rows()" method.

Miscellaneous Questions
       5.1 Can I do multi-threading with DBI?

       Perl version 5.005 and later can be built to support multi-threading.
       The DBI, as of version 1.02, does not yet support multi-threading so it
       would be unsafe to let more than one thread enter the DBI at the same
       time.

       It is expected that some future version of the DBI will at least be
       thread-safe (but not thread-hot) by automatically blocking threads
       intering the DBI while it's already in use.

       For some OCI example code for Oracle that has multi-threaded "SELECT"
       statements, see:

           http://www.symbolstone.org/technology/oracle/oci/orathreads.tar.gz

       5.2 How do I handle BLOB data with DBI?

       Handling BLOB data with the DBI is very straight-forward. BLOB columns
       are specified in a SELECT statement as per normal columns. However, you
       also need to specify a maximum BLOB size that the <I>database
       handle</I> can fetch using the "LongReadLen" attribute.

       For example:

           ### $dbh is a connected database handle
           $sth = $dbh->prepare( "SELECT blob_column FROM blobby_table" );
           $sth->execute;

       would fail.

           ### $dbh is a connected database handle
           ### Set the maximum BLOB size...
           $dbh->{LongReadLen} = 16384;        ### 16Kb...Not much of a BLOB!

           $sth = $dbh->prepare( "..." );

       would succeed <I>provided no column values were larger than the
       specified value</I>.

       If the BLOB data is longer than the value of "LongReadLen", then an
       error will occur. However, the DBI provides an additional piece of
       functionality that will automatically truncate the fetched BLOB to the
       size of "LongReadLen" if it is longer. This does not cause an error to
       occur, but may make your fetched BLOB data useless.

       This behaviour is regulated by the "LongTruncOk" attribute which is
       defaultly set to a false value ( thus making overlong BLOB fetches fail
       ).

           ### Set BLOB handling such that it's 16Kb and can be truncated
           $dbh->{LongReadLen} = 16384;
           $dbh->{LongTruncOk} = 1;

       Truncation of BLOB data may not be a big deal in cases where the BLOB
       contains run-length encoded data, but data containing checksums at the
       end, for example, a ZIP file, would be rendered useless.

       5.3 How can I invoke stored procedures with DBI?

       The DBI does not define a database-independent way of calling stored
       procedures.

       However, most database that support them also provide a way to call
       them from SQL statements - and the DBI certainly supports that.

       So, assuming that you have created a stored procedure within the target
       database, eg, an Oracle database, you can use $dbh->"do()" to
       immediately execute the procedure. For example,

           $dbh->do( "BEGIN someProcedure; END;" );   # Oracle-specific

       You should also be able to "prepare" and "execute", which is the
       recommended way if you'll be calling the procedure often.

       5.4 How can I get return values from stored procedures with DBI?

           Contributed by Jeff Urlwin

           $sth = $dbh->prepare( "BEGIN foo(:1, :2, :3); END;" );
           $sth->bind_param(1, $a);
           $sth->bind_param_inout(2, \$path, 2000);
           $sth->bind_param_inout(3, \$success, 2000);
           $sth->execute;

       Remember to perform error checking, though! ( Or use the "RaiseError"
       attribute ).

       5.5 How can I create or drop a database with DBI?

       Database creation and deletion are concepts that are entirely too
       abstract to be adequately supported by DBI. For example, Oracle does
       not support the concept of dropping a database at all! Also, in Oracle,
       the database server essentially is the database, whereas in mSQL, the
       server process runs happily without any databases created in it. The
       problem is too disparate to attack in a worthwhile way.

       Some drivers, therefore, support database creation and deletion through
       the private "func()" methods. You should check the documentation for
       the drivers you are using to see if they support this mechanism.

       5.6 How can I "commit" or "rollback" a statement with DBI?

       See the "commit()" and "rollback()" methods in the DBI Specification.

       Chapter 6 of "Programming the Perl DBI" discusses transaction handling
       within the context of DBI in more detail.

       5.7 How are "NULL" values handled by DBI?

       "NULL" values in DBI are specified to be treated as the value "undef".
       "NULL"s can be inserted into databases as "NULL", for example:

           $rv = $dbh->do( "INSERT INTO table VALUES( NULL )" );

       but when queried back, the "NULL"s should be tested against "undef".
       This is standard across all drivers.

       5.8 What are these "func()" methods all about?

       The "func()" method is defined within DBI as being an entry point for
       database-specific functionality, eg, the ability to create or drop
       databases. Invoking these driver-specific methods is simple, for
       example, to invoke a "createDatabase" method that has one argument, we
       would write:

           $rv =$dbh->func( 'argument', 'createDatabase' );

       Software developers should note that the "func()" methods are non-
       portable between databases.

       5.9 Is DBI Year 2000 Compliant?

       DBI has no knowledge of understanding of what dates are. Therefore, DBI
       itself does not have a Year 2000 problem. Individual drivers may use
       date handling code internally and therefore be potentially susceptible
       to the Year 2000 problem, but this is unlikely.

       You may also wish to read the ``Does Perl have a Year 2000 problem?''
       section of the Perl FAQ at:

           http://www.perl.com/CPAN/doc/FAQs/FAQ/PerlFAQ.html

Support and Training
       The Perl5 Database Interface is FREE software. IT COMES WITHOUT
       WARRANTY OF ANY KIND. See the DBI README for more details.

       However, some organizations are providing either technical support or
       training programs on DBI. The present author has no knowledge as to the
       quality of these services. The links are included for reference
       purposes only and should not be regarded as recommendations in any way.
       Caveat emptor.

       Commercial Support

       The Perl Clinic
           The Perl Clinic provides commercial support for Perl and Perl
           related problems, including the DBI and its drivers.  Support is
           provided by the company with whom Tim Bunce, author of DBI and
           DBD::Oracle, works and ActiveState. For more information on their
           services, please see:

               http://www.perlclinic.com

       Training

       Westlake Solutions
           A hands-on class for experienced Perl CGI developers that teaches
           how to write database-connected CGI scripts using Perl and DBI.pm.
           This course, along with four other courses on CGI scripting with
           Perl, is taught in Washington, DC; Arlington, Virginia; and on-site
           worldwide upon request.

           See:

               http://www.westlake.com/training

           for more details.

Other References
       In this section, we present some miscellaneous WWW links that may be of
       some interest to DBI users. These are not verified and may result in
       unknown sites or missing documents.

           http://www-ccs.cs.umass.edu/db.html
           http://www.odmg.org/odmg93/updates_dbarry.html
           http://www.jcc.com/sql_stnd.html

AUTHOR
       Alligator Descartes <http://www.symbolstone.org/descarte/contact.html>.
       Portions are Copyright their original stated authors.

COPYRIGHT
       This document is Copyright (c)1994-2000 Alligator Descartes, with
       portions Copyright (c)1994-2000 their original authors. This module is
       released under the 'Artistic' license which you can find in the perl
       distribution.

       This document is Copyright (c)1997-2000 Alligator Descartes. All rights
       reserved.  Permission to distribute this document, in full or in part,
       via email, Usenet, ftp archives or http is granted providing that no
       charges are involved, reasonable attempt is made to use the most
       current version and all credits and copyright notices are retained (
       the AUTHOR and COPYRIGHT sections ).  Requests for other distribution
       rights, including incorporation into commercial products, such as
       books, magazine articles or CD-ROMs should be made to Alligator
       Descartes <http://www.symbolstone.org/descarte/contact.html>.



perl v5.10.0                      2007-11-15                     DBI::FAQ(3pm)