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DBI::FAQ(3pm) - phpMan

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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/>

       Neither this document nor that web site are actively maintained.  Volunteers are welcome.

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 & 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 independent 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
                                           <mpeppler AT itf.ch>
           Oraperl     Oracle 6 & 7        Kevin Stock     DBD::Oracle
                                           <dbi-users AT perl.org>
           Ingperl     Ingres              Tim Bunce &     DBD::Ingres
                                           Ted Lemon
                                           <dbi-users AT perl.org>
           Interperl   Interbase           Buzz Moschetti  DBD::Interbase
                                           <buzz AT bear.com>
           Uniperl     Unify 5.0           Rick Wargo      None
                                           <rickers AT coe.edu>
           Pgperl      Postgres            Igor Metz       DBD::Pg
                                           <metz AT iam.ch>
           Btreeperl   NDBM                John Conover    SDBM?
                                           <john AT johncon.com>
           Ctreeperl   C-Tree              John Conover    None
                                           <john AT johncon.com>
           Cisamperl   Informix C-ISAM     Mathias Koerber None
                                           <mathias AT unicorn.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/

       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/

           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

           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/

           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/

       Mailing Lists
           There are three mailing lists for DBI:

               dbi-announce AT perl.org     -- for announcements, very low traffic
               dbi-users AT perl.org        -- general user support
               dbi-dev AT perl.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-help AT perl.org
               dbi-users-help AT perl.org
               dbi-dev-help AT perl.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/

       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:

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

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

           ·   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:

           ·   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.

           ·   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

           ·   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 there a DBD for <insert favourite database here>?
       First check if a driver is available on CPAN by searching for the name of the database
       (including common abbreviations and aliases).

       Here's a general query that'll match all distributions:

           http://search.cpan.org/search?query=DBD&mode=dist

       If you can't find a driver that way, you could check if the database supports ODBC
       drivers. If so then you could probably use the DBD::ODBC driver:

           http://search.cpan.org/dist/DBD-ODBC/

       If not, then try asking on the dbi-users mailing list.

   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 scalable 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 <insert feature here> 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 entering the DBI while it's already in use.

   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 set to a false value
       by default ( 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.  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.



perl v5.20.0                                2013-06-24                              DBI::FAQ(3pm)


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