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DBI::FAQ(3) User Contributed Perl Documentation DBI::FAQ(3)
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.
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 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 what-
ever 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
Oraperl Oracle 6 & 7 Kevin Stock DBD::Oracle
Ingperl Ingres Tim Bunce & DBD::Ingres
Ted Lemon
Interperl Interbase Buzz Moschetti DBD::Interbase
Uniperl Unify 5.0 Rick Wargo None
Pgperl Postgres Igor Metz DBD::Pg
Btreeperl NDBM John Conover SDBM?
Ctreeperl C-Tree John Conover None
Cisamperl Informix C-ISAM Mathias Koerber None
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 mod-
ule 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 via 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 documenta-
tion 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
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 perma-
nently, or conveniently, connected to the Inter-
net. 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 inter-
ested 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 con-
tain 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 com-
pliant 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 com-
prehensive documents. These are quite often varying in
quality, but do provide some insights into the work-
ings 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 occasion-
ally 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:
-- for announcements, very low traffic
-- general user support
-- for driver developers (no user support)
For information on how to subscribe, set digest mode
etc, and unsubscribe, send an email message (the con-
tent will be ignored) to:
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:
· 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 ver-
sion, 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 plat-
form 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 fur-
nish 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, operat-
ing system versions and any other pertinent infor-
mation.
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 mail-
ing 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 program-
ming 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 sim-
ple things easy while still making the hard things possi-
ble. 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 pre-
pared 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 insert favourite database here>?
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 inten-
tion 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, ques-
tions 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, pro-
posed 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 power-
ful 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 consider-
ing. 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 sponsor-
ship 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 vari-
ables, in the case of DBD::Oracle, variables like "ORA-
CLE_HOME", "ORACLE_SID" or "TWO_TASK".
The "httpd" process usually runs under the user id of
"nobody", which implies there is no configured environ-
ment. 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 fur-
ther 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 maxi-
mum BLOB size that the database handle 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 provided no column values were larger
than the specified value.
If the BLOB data is longer than the value of "Lon-
gReadLen", then an error will occur. However, the DBI pro-
vides an additional piece of functionality that will auto-
matically truncate the fetched BLOB to the size of "Lon-
gReadLen" 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 cer-
tainly 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 drop-
ping 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 worth-
while 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 transac-
tion 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 docu-
ments.
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.symbol-
stone.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 distri-
bution.
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 cur-
rent 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>.
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