mysql.pm

Astercon2 开源软交换 2.2.0

Similar to mysql, but type names and not numbers are returned.
Whenever possible, the ANSI SQL name is preferred.

=item mysql_warning_count

The number of warnings generated during execution of the SQL statement.

=back

=head1 TRANSACTION SUPPORT

Beginning with DBD::mysql 2.0416, transactions are supported.
The transaction support works as follows:

=over

=item *

By default AutoCommit mode is on, following the DBI specifications.

=item *

If you execute

    $dbh->{'AutoCommit'} = 0;

or

    $dbh->{'AutoCommit'} = 1;

then the driver will set the MySQL server variable autocommit to 0 or
1, respectively. Switching from 0 to 1 will also issue a COMMIT,
following the DBI specifications.

=item *

The methods

    $dbh->rollback();
    $dbh->commit();

will issue the commands COMMIT and ROLLBACK, respectively. A
ROLLBACK will also be issued if AutoCommit mode is off and the
database handles DESTROY method is called. Again, this is following
the DBI specifications.

=back

Given the above, you should note the following:

=over

=item *

You should never change the server variable autocommit manually,
unless you are ignoring DBI's transaction support.

=item *

Switching AutoCommit mode from on to off or vice versa may fail.
You should always check for errors, when changing AutoCommit mode.
The suggested way of doing so is using the DBI flag RaiseError.
If you don't like RaiseError, you have to use code like the
following:

  $dbh->{'AutoCommit'} = 0;
  if ($dbh->{'AutoCommit'}) {
    # An error occurred!
  }

=item *

If you detect an error while changing the AutoCommit mode, you
should no longer use the database handle. In other words, you
should disconnect and reconnect again, because the transaction
mode is unpredictable. Alternatively you may verify the transaction
mode by checking the value of the server variable autocommit.
However, such behaviour isn't portable.

=item *

DBD::mysql has a "reconnect" feature that handles the so-called
MySQL "morning bug": If the server has disconnected, most probably
due to a timeout, then by default the driver will reconnect and
attempt to execute the same SQL statement again. However, this
behaviour is disabled when AutoCommit is off: Otherwise the
transaction state would be completely unpredictable after a
reconnect.  

=item *

The "reconnect" feature of DBD::mysql can be toggled by using the
L<mysql_auto_reconnect> attribute. This behaviour should be turned off
in code that uses LOCK TABLE because if the database server time out
and DBD::mysql reconnect, table locks will be lost without any 
indication of such loss.

=back

=over

=head1 MULTIPLE RESULT SETS

As of version 3.0002_5, DBD::mysql supports multiple result sets (Thanks
to Guy Harrison!). This is the first release of this functionality, so 
there may be issues. Please report bugs if you run into them!

The basic usage of multiple result sets is

  do 
  {
    while (@row= $sth->fetchrow_array())
    {
      do stuff;
    }
  } while ($sth->more_results)

An example would be:

  $dbh->do("drop procedure if exists someproc") or print $DBI::errstr;

  $dbh->do("create procedure somproc() deterministic
   begin
   declare a,b,c,d int;
   set a=1;
   set b=2;
   set c=3;
   set d=4;
   select a, b, c, d;
   select d, c, b, a;
   select b, a, c, d;
   select c, b, d, a;
  end") or print $DBI::errstr;

  $sth=$dbh->prepare('call someproc()') || 
  die $DBI::err.": ".$DBI::errstr;

  $sth->execute || die DBI::err.": ".$DBI::errstr; $rowset=0;
  do {
    print "\nRowset ".++$i."\n---------------------------------------\n\n";
    foreach $colno (0..$sth->{NUM_OF_FIELDS}) {
      print $sth->{NAME}->[$colno]."\t";
    }
    print "\n";
    while (@row= $sth->fetchrow_array())  {
      foreach $field (0..$#row) {
        print $row[$field]."\t";
      }
      print "\n";
    }
  } until (!$sth->more_results)
 
For more examples, please see the eg/ directory. This is where helpful
DBD::mysql code snippits will be added in the future.

=head2 Issues with Multiple result sets

So far, the main issue is if your result sets are "jagged", meaning, the
number of columns of your results vary. Varying numbers of columns could
result in your script crashing. This is something that will be fixed soon.


=head1 MULTITHREADING

The multithreading capabilities of DBD::mysql depend completely
on the underlying C libraries: The modules are working with handle data
only, no global variables are accessed or (to the best of my knowledge)
thread unsafe functions are called. Thus DBD::mysql is believed
to be completely thread safe, if the C libraries are thread safe
and you don't share handles among threads.

The obvious question is: Are the C libraries thread safe?
In the case of MySQL the answer is "mostly" and, in theory, you should
be able to get a "yes", if the C library is compiled for being thread
safe (By default it isn't.) by passing the option -with-thread-safe-client
to configure. See the section on I<How to make a threadsafe client> in
the manual.


=head1 INSTALLATION

Windows users may skip this section and pass over to L<WIN32
INSTALLATION> below. Others, go on reading.

First of all, you do not need an installed MySQL server for installing
DBD::mysql. However, you need at least the client
libraries and possibly the header files, if you are compiling DBD::mysql
from source. In the case of MySQL you can create a
client-only version by using the configure option --without-server.
If you are using precompiled binaries, then it may be possible to
use just selected RPM's like MySQL-client and MySQL-devel or something
similar, depending on the distribution.

First you need to install the DBI module. For using I<dbimon>, a
simple DBI shell it is recommended to install Data::ShowTable another
Perl module.

I recommend trying automatic installation via the CPAN module. Try

  perl -MCPAN -e shell

If you are using the CPAN module for the first time, it will prompt
you a lot of questions. If you finally receive the CPAN prompt, enter

  install Bundle::DBD::mysql

If this fails (which may be the case for a number of reasons, for
example because you are behind a firewall or don't have network
access), you need to do a manual installation. First of all you
need to fetch the modules from CPAN search

   http://search.cpan.org/ 

The following modules are required

  DBI
  Data::ShowTable
  DBD::mysql

Then enter the following commands (note - versions are just examples):

  gzip -cd DBI-(version).tar.gz | tar xf -
  cd DBI-(version)
  perl Makefile.PL
  make
  make test
  make install

  cd ..
  gzip -cd Data-ShowTable-(version).tar.gz | tar xf -
  cd Data-ShowTable-3.3
  perl Makefile.PL
  make
  make install

  cd ..
  gzip -cd DBD-mysql-(version)-tar.gz | tar xf -
  cd DBD-mysql-(version)
  perl Makefile.PL
  make
  make test
  make install

During "perl Makefile.PL" you will be prompted some questions.
Other questions are the directories with header files and libraries.
For example, of your file F<mysql.h> is in F</usr/include/mysql/mysql.h>,
then enter the header directory F</usr>, likewise for
F</usr/lib/mysql/libmysqlclient.a> or F</usr/lib/libmysqlclient.so>.


=head1 WIN32 INSTALLATION

If you are using ActivePerl, you may use ppm to install DBD-mysql.
For Perl 5.6, upgrade to Build 623 or later, then it is sufficient
to run

  ppm install DBI
  ppm install DBD::mysql

If you need an HTTP proxy, you might need to set the environment
variable http_proxy, for example like this:

  set http_proxy=http://myproxy.com:8080/

As of this writing, DBD::mysql is missing in the ActivePerl 5.8.0
repository. However, Randy Kobes has kindly donated an own
distribution and the following might succeed:

  ppm install http://theoryx5.uwinnipeg.ca/ppms/DBD-mysql.ppd

Otherwise you definitely *need* a C compiler. And it *must* be the same
compiler that was being used for compiling Perl itself. If you don't
have a C compiler, the file README.win32 from the Perl source
distribution tells you where to obtain freely distributable C compilers
like egcs or gcc. The Perl sources are available via CPAN search

  http://search.cpan.org

I recommend using the win32clients package for installing DBD::mysql
under Win32, available for download on www.tcx.se. The following steps
have been required for me:

=over

=item -

The current Perl versions (5.6, as of this writing) do have a problem
with detecting the C libraries. I recommend to apply the following
patch:

  *** c:\Perl\lib\ExtUtils\Liblist.pm.orig Sat Apr 15 20:03:40 2000
  --- c:\Perl\lib\ExtUtils\Liblist.pm      Sat Apr 15 20:03:45 2000
  ***************
  *** 230,235 ****
  --- 230,239 ----
      # add "$Config{installarchlib}/CORE" to default search path
      push @libpath, "$Config{installarchlib}/CORE";

  +     if ($VC  and  exists($ENV{LIB})  and  defined($ENV{LIB})) {
  +       push(@libpath, split(/;/, $ENV{LIB}));
  +     }
  +
      foreach (Text::ParseWords::quotewords('\s+', 0, $potential_libs)){

        $thislib = $_;
                                                                       
=item -

Extract sources into F<C:\>. This will create a directory F<C:\mysql>
with subdirectories include and lib.

IMPORTANT: Make sure this subdirectory is not shared by other TCX
files! In particular do *not* store the MySQL server in the same
directory. If the server is already installed in F<C:\mysql>,
choose a location like F<C:\tmp>, extract the win32clients there.
Note that you can remove this directory entirely once you have
installed DBD::mysql.

=item -

Extract the DBD::mysql sources into another directory, for
example F<C:\src\siteperl>

=item -

Open a DOS shell and change directory to F<C:\src\siteperl>.

=item -

The next step is only required if you repeat building the modules: Make
sure that you have a clean build tree by running

  nmake realclean

If you don't have VC++, replace nmake with your flavour of make. If
error messages are reported in this step, you may safely ignore them.

=item -

Run

  perl Makefile.PL

which will prompt you for some settings. The really important ones are:

  Which DBMS do you want to use?

enter a 1 here (MySQL only), and

  Where is your mysql installed? Please tell me the directory that
  contains the subdir include.

where you have to enter the win32clients directory, for example
F<C:\mysql> or F<C:\tmp\mysql>.

=item -

Continued in the usual way:

  nmake
  nmake install

=back

If you want to create a PPM package for the ActiveState Perl version, then
modify the above steps as follows: Run

  perl Makefile.PL NAME=DBD-mysql BINARY_LOCATION=DBD-mysql.tar.gz
  nmake ppd
  nmake

Once that is done, use tar and gzip (for example those from the CygWin32
distribution) to create an archive:

  mkdir x86
  tar cf x86/DBD-mysql.tar blib
  gzip x86/DBD-mysql.tar

Put the files x86/DBD-mysql.tar.gz and DBD-mysql.ppd onto some WWW server
and install them by typing

  install http://your.server.name/your/directory/DBD-mysql.ppd

in the PPM program.


=head1 AUTHORS

The current version of B<DBD::mysql> is almost completely written
by Jochen Wiedmann, and is now being maintained by
Patrick Galbraith (I<[e-mail]>). 
The first version's author was Alligator Descartes, who was aided
and abetted by Gary Shea, Andreas K鰊ig and Tim Bunce amongst others.

The B<Mysql> module was originally written by Andreas K鰊ig
<[e-mail]>. The current version, mainly an emulation
layer, is from Jochen Wiedmann.


=head1 COPYRIGHT


This module is 
Large Portions Copyright (c) 2004-2006 MySQL Patrick Galbraith, Alexey Stroganov,
Large Portions Copyright (c) 2003-2005 Rudolf Lippan; Large Portions 
Copyright (c) 1997-2003 Jochen Wiedmann, with code portions 
Copyright (c)1994-1997 their original authors This module is
released under the same license as Perl itself. See the Perl README
for details.


=head1 MAILING LIST SUPPORT

This module is maintained and supported on a mailing list,

    [e-mail]

To subscribe to this list, go to

http://lists.mysql.com/perl?sub=1

Mailing list archives are available at

http://lists.mysql.com/perl

Additionally you might try the dbi-user mailing list for questions about
DBI and its modules in general. Subscribe via

[e-mail]

Mailing list archives are at

http://groups.google.com/group/perl.dbi.users?hl=en&lr=

Also, the main DBI site is at

http://dbi.perl.org/

=head1 ADDITIONAL DBI INFORMATION

Additional information on the DBI project can be found on the World
Wide Web at the following URL:

    http://dbi.perl.org

where documentation, pointers to the mailing lists and mailing list
archives and pointers to the most current versions of the modules can
be used.

Information on the DBI interface itself can be gained by typing:

    perldoc DBI

right now!


=head1 BUG REPORTING, ENHANCEMENT/FEATURE REQUESTS

Please report bugs, including all the information needed
such as DBD::mysql version, MySQL version, OS type/version, etc
to this link:

http://bugs.mysql.com/


=cut