Provided by: libdbd-mysql-perl_4.052-1ubuntu3_amd64 bug

NAME

       DBD::mysql - MySQL driver for the Perl5 Database Interface (DBI)

SYNOPSIS

           use DBI;

           my $dsn = "DBI:mysql:database=$database;host=$hostname;port=$port";
           my $dbh = DBI->connect($dsn, $user, $password);

           my $sth = $dbh->prepare(
               'SELECT id, first_name, last_name FROM authors WHERE last_name = ?')
               or die "prepare statement failed: $dbh->errstr()";
           $sth->execute('Eggers') or die "execution failed: $dbh->errstr()";
           print $sth->rows . " rows found.\n";
           while (my $ref = $sth->fetchrow_hashref()) {
               print "Found a row: id = $ref->{'id'}, fn = $ref->{'first_name'}\n";
           }
           $sth->finish;

EXAMPLE

         #!/usr/bin/perl

         use strict;
         use warnings;
         use DBI;

         # Connect to the database.
         my $dbh = DBI->connect("DBI:mysql:database=test;host=localhost",
                                "joe", "joe's password",
                                {'RaiseError' => 1});

         # Drop table 'foo'. This may fail, if 'foo' doesn't exist
         # Thus we put an eval around it.
         eval { $dbh->do("DROP TABLE foo") };
         print "Dropping foo failed: $@\n" if $@;

         # Create a new table 'foo'. This must not fail, thus we don't
         # catch errors.
         $dbh->do("CREATE TABLE foo (id INTEGER, name VARCHAR(20))");

         # INSERT some data into 'foo'. We are using $dbh->quote() for
         # quoting the name.
         $dbh->do("INSERT INTO foo VALUES (1, " . $dbh->quote("Tim") . ")");

         # same thing, but using placeholders (recommended!)
         $dbh->do("INSERT INTO foo VALUES (?, ?)", undef, 2, "Jochen");

         # now retrieve data from the table.
         my $sth = $dbh->prepare("SELECT * FROM foo");
         $sth->execute();
         while (my $ref = $sth->fetchrow_hashref()) {
           print "Found a row: id = $ref->{'id'}, name = $ref->{'name'}\n";
         }
         $sth->finish();

         # Disconnect from the database.
         $dbh->disconnect();

DESCRIPTION

       DBD::mysql is the Perl5 Database Interface driver for the MySQL database. In other words:
       DBD::mysql is an interface between the Perl programming language and the MySQL programming
       API that comes with the MySQL relational database management system. Most functions
       provided by this programming API are supported. Some rarely used functions are missing,
       mainly because no-one ever requested them. :-)

       In what follows we first discuss the use of DBD::mysql, because this is what you will need
       the most. For installation, see the separate document DBD::mysql::INSTALL.  See "EXAMPLE"
       for a simple example above.

       From perl you activate the interface with the statement

         use DBI;

       After that you can connect to multiple MySQL database servers and send multiple queries to
       any of them via a simple object oriented interface. Two types of objects are available:
       database handles and statement handles. Perl returns a database handle to the connect
       method like so:

         $dbh = DBI->connect("DBI:mysql:database=$db;host=$host",
           $user, $password, {RaiseError => 1});

       Once you have connected to a database, you can execute SQL statements with:

         my $query = sprintf("INSERT INTO foo VALUES (%d, %s)",
                             $number, $dbh->quote("name"));
         $dbh->do($query);

       See DBI for details on the quote and do methods. An alternative approach is

         $dbh->do("INSERT INTO foo VALUES (?, ?)", undef,
                  $number, $name);

       in which case the quote method is executed automatically. See also the bind_param method
       in DBI. See "DATABASE HANDLES" below for more details on database handles.

       If you want to retrieve results, you need to create a so-called statement handle with:

         $sth = $dbh->prepare("SELECT * FROM $table");
         $sth->execute();

       This statement handle can be used for multiple things. First of all you can retrieve a row
       of data:

         my $row = $sth->fetchrow_hashref();

       If your table has columns ID and NAME, then $row will be hash ref with keys ID and NAME.
       See "STATEMENT HANDLES" below for more details on statement handles.

       But now for a more formal approach:

   Class Methods
       connect
               use DBI;

               $dsn = "DBI:mysql:$database";
               $dsn = "DBI:mysql:database=$database;host=$hostname";
               $dsn = "DBI:mysql:database=$database;host=$hostname;port=$port";

               $dbh = DBI->connect($dsn, $user, $password);

           The "database" is not a required attribute, but please note that MySQL has no such
           thing as a default database. If you don't specify the database at connection time your
           active database will be null and you'd need to prefix your tables with the database
           name; i.e. 'SELECT * FROM mydb.mytable'.

           This is similar to the behavior of the mysql command line client. Also, 'SELECT
           DATABASE()' will return the current database active for the handle.

           host
           port
               The hostname, if not specified or specified as '' or 'localhost', will default to
               a MySQL server running on the local machine using the default for the UNIX socket.
               To connect to a MySQL server on the local machine via TCP, you must specify the
               loopback IP address (127.0.0.1) as the host.

               Should the MySQL server be running on a non-standard port number, you may
               explicitly state the port number to connect to in the "hostname" argument, by
               concatenating the hostname and port number together separated by a colon ( ":" )
               character or by using the  "port" argument.

               To connect to a MySQL server on localhost using TCP/IP, you must specify the
               hostname as 127.0.0.1 (with the optional port).

               When connecting to a MySQL Server with IPv6, a bracketed IPv6 address should be
               used.  Example DSN:

                 my $dsn = "DBI:mysql:;host=[1a12:2800:6f2:85::f20:8cf];port=3306";

           mysql_client_found_rows
               If TRUE (Default), sets the CLIENT_FOUND_ROWS flag when connecting to MySQL.  This
               causes UPDATE statements to return the number of rows *matched*, not the number of
               rows actually changed.

               If you want the number of rows changed in response to an UPDATE statement, specify
               "mysql_client_found_rows=0" in the DSN.

           mysql_compression
               If your DSN contains the option "mysql_compression=1", then the communication
               between client and server will be compressed.

           mysql_connect_timeout
               If your DSN contains the option "mysql_connect_timeout=##", the connect request to
               the server will timeout if it has not been successful after the given number of
               seconds.

           mysql_write_timeout
               If your DSN contains the option "mysql_write_timeout=##", the write operation to
               the server will timeout if it has not been successful after the given number of
               seconds.

           mysql_read_timeout
               If your DSN contains the option "mysql_read_timeout=##", the read operation to the
               server will timeout if it has not been successful after the given number of
               seconds.

           mysql_init_command
               If your DSN contains the option "mysql_init_command=##", then this SQL statement
               is executed when connecting to the MySQL server.  It is automatically re-executed
               if reconnection occurs.

           mysql_skip_secure_auth
               This option is for older mysql databases that don't have secure auth set.

           mysql_read_default_file
           mysql_read_default_group
               These options can be used to read a config file like /etc/my.cnf or ~/.my.cnf. By
               default MySQL's C client library doesn't use any config files unlike the client
               programs (mysql, mysqladmin, ...) that do, but outside of the C client library.
               Thus you need to explicitly request reading a config file, as in

                   $dsn = "DBI:mysql:test;mysql_read_default_file=/home/joe/my.cnf";
                   $dbh = DBI->connect($dsn, $user, $password)

               The option mysql_read_default_group can be used to specify the default group in
               the config file: Usually this is the client group, but see the following example:

                   [client]
                   host=localhost

                   [perl]
                   host=perlhost

               (Note the order of the entries! The example won't work, if you reverse the
               [client] and [perl] sections!)

               If you read this config file, then you'll be typically connected to localhost.
               However, by using

                   $dsn = "DBI:mysql:test;mysql_read_default_group=perl;"
                       . "mysql_read_default_file=/home/joe/my.cnf";
                   $dbh = DBI->connect($dsn, $user, $password);

               you'll be connected to perlhost. Note that if you specify a default group and do
               not specify a file, then the default config files will all be read.  See the
               documentation of the C function mysql_options() for details.

           mysql_socket
               It is possible to choose the Unix socket that is used for connecting to the
               server. This is done, for example, with

                   mysql_socket=/dev/mysql

               Usually there's no need for this option, unless you are using another location for
               the socket than that built into the client.

           mysql_ssl
               A true value turns on the CLIENT_SSL flag when connecting to the MySQL server and
               enforce SSL encryption.  A false value (which is default) disable SSL encryption
               with the MySQL server.

               When enabling SSL encryption you should set also other SSL options, at least
               mysql_ssl_ca_file or mysql_ssl_ca_path.

                 mysql_ssl=1 mysql_ssl_verify_server_cert=1 mysql_ssl_ca_file=/path/to/ca_cert.pem

               This means that your communication with the server will be encrypted.

               Please note that this can only work if you enabled SSL when compiling DBD::mysql;
               this is the default starting version 4.034.  See DBD::mysql::INSTALL for more
               details.

           mysql_ssl_ca_file
               The path to a file in PEM format that contains a list of trusted SSL certificate
               authorities.

               When set MySQL server certificate is checked that it is signed by some CA
               certificate in the list.  Common Name value is not verified unless
               "mysql_ssl_verify_server_cert" is enabled.

           mysql_ssl_ca_path
               The path to a directory that contains trusted SSL certificate authority
               certificates in PEM format.

               When set MySQL server certificate is checked that it is signed by some CA
               certificate in the list.  Common Name value is not verified unless
               "mysql_ssl_verify_server_cert" is enabled.

               Please note that this option is supported only if your MySQL client was compiled
               with OpenSSL library, and not with default yaSSL library.

           mysql_ssl_verify_server_cert
               Checks the server's Common Name value in the certificate that the server sends to
               the client.  The client verifies that name against the host name the client uses
               for connecting to the server, and the connection fails if there is a mismatch.
               For encrypted connections, this option helps prevent man-in-the-middle attacks.

               Verification of the host name is disabled by default.

           mysql_ssl_client_key
               The name of the SSL key file in PEM format to use for establishing a secure
               connection.

           mysql_ssl_client_cert
               The name of the SSL certificate file in PEM format to use for establishing a
               secure connection.

           mysql_ssl_cipher
               A list of permissible ciphers to use for connection encryption.  If no cipher in
               the list is supported, encrypted connections will not work.

                 mysql_ssl_cipher=AES128-SHA
                 mysql_ssl_cipher=DHE-RSA-AES256-SHA:AES128-SHA

           mysql_ssl_optional
               Setting "mysql_ssl_optional" to true disables strict SSL enforcement and makes SSL
               connection optional.  This option opens security hole for man-in-the-middle
               attacks.  Default value is false which means that "mysql_ssl" set to true enforce
               SSL encryption.

               This option was introduced in 4.043 version of DBD::mysql.  Due to The BACKRONYM
               <http://backronym.fail/> and The Riddle <http://riddle.link/> vulnerabilities in
               libmysqlclient library, enforcement of SSL encryption was not possbile and
               therefore "mysql_ssl_optional=1" was effectively set for all DBD::mysql versions
               prior to 4.043.  Starting with 4.043, DBD::mysql with "mysql_ssl=1" could refuse
               connection to MySQL server if underlaying libmysqlclient library is vulnerable.
               Option "mysql_ssl_optional" can be used to make SSL connection vulnerable.

           mysql_server_pubkey
               Path to the RSA public key of the server. This is used for the sha256_password and
               caching_sha2_password authentication plugins.

           mysql_get_server_pubkey
               Setting "mysql_get_server_pubkey" to true requests the public RSA key of the
               server.

           mysql_local_infile
               The LOCAL capability for LOAD DATA may be disabled in the MySQL client library by
               default. If your DSN contains the option "mysql_local_infile=1", LOAD DATA LOCAL
               will be enabled.  (However, this option is *ineffective* if the server has also
               been configured to disallow LOCAL.)

           mysql_multi_statements
               Support for multiple statements separated by a semicolon (;) may be enabled by
               using this option. Enabling this option may cause problems if server-side prepared
               statements are also enabled.

           mysql_server_prepare
               This option is used to enable server side prepared statements.

               To use server side prepared statements, all you need to do is set the variable
               mysql_server_prepare in the connect:

                 $dbh = DBI->connect(
                   "DBI:mysql:database=test;host=localhost;mysql_server_prepare=1",
                   "",
                   "",
                   { RaiseError => 1, AutoCommit => 1 }
                 );

               or:

                 $dbh = DBI->connect(
                   "DBI:mysql:database=test;host=localhost",
                   "",
                   "",
                   { RaiseError => 1, AutoCommit => 1, mysql_server_prepare => 1 }
                 );

               There are many benefits to using server side prepare statements, mostly if you are
               performing many inserts because of that fact that a single statement is prepared
               to accept multiple insert values.

               To make sure that the 'make test' step tests whether server prepare works, you
               just need to export the env variable MYSQL_SERVER_PREPARE:

                 export MYSQL_SERVER_PREPARE=1

               Please note that mysql server cannot prepare or execute some prepared statements.
               In this case DBD::mysql fallbacks to normal non-prepared statement and tries
               again.

           mysql_server_prepare_disable_fallback
               This option disable fallback to normal non-prepared statement when mysql server
               does not support execution of current statement as prepared.

               Useful when you want to be sure that statement is going to be executed as server
               side prepared. Error message and code in case of failure is propagated back to
               DBI.

           mysql_embedded_options
               The option <mysql_embedded_options> can be used to pass 'command-line' options to
               embedded server.

               Example:

                 use DBI;
                 $testdsn="DBI:mysqlEmb:database=test;mysql_embedded_options=--help,--verbose";
                 $dbh = DBI->connect($testdsn,"a","b");

               This would cause the command line help to the embedded MySQL server library to be
               printed.

           mysql_embedded_groups
               The option <mysql_embedded_groups> can be used to specify the groups in the config
               file(my.cnf) which will be used to get options for embedded server.  If not
               specified [server] and [embedded] groups will be used.

               Example:

                 $testdsn="DBI:mysqlEmb:database=test;mysql_embedded_groups=embedded_server,common";

           mysql_conn_attrs
               The option <mysql_conn_attrs> is a hash of attribute names and values which can be
               used to send custom connection attributes to the server. Some attributes like
               '_os', '_platform', '_client_name' and '_client_version' are added by
               libmysqlclient and 'program_name' is added by DBD::mysql.

               You can then later read these attributes from the performance schema tables which
               can be quite helpful for profiling your database or creating statistics.  You'll
               have to use a MySQL 5.6 server and libmysqlclient or newer to leverage this
               feature.

                 my $dbh= DBI->connect($dsn, $user, $password,
                   { AutoCommit => 0,
                     mysql_conn_attrs => {
                       foo => 'bar',
                       wiz => 'bang'
                     },
                   });

               Now you can select the results from the performance schema tables. You can do this
               in the same session, but also afterwards. It can be very useful to answer
               questions like 'which script sent this query?'.

                 my $results = $dbh->selectall_hashref(
                   'SELECT * FROM performance_schema.session_connect_attrs',
                   'ATTR_NAME'
                 );

               This returns:

                 $result = {
                   'foo' => {
                       'ATTR_VALUE'       => 'bar',
                       'PROCESSLIST_ID'   => '3',
                       'ATTR_NAME'        => 'foo',
                       'ORDINAL_POSITION' => '6'
                   },
                   'wiz' => {
                       'ATTR_VALUE'       => 'bang',
                       'PROCESSLIST_ID'   => '3',
                       'ATTR_NAME'        => 'wiz',
                       'ORDINAL_POSITION' => '3'
                   },
                   'program_name' => {
                       'ATTR_VALUE'       => './foo.pl',
                       'PROCESSLIST_ID'   => '3',
                       'ATTR_NAME'        => 'program_name',
                       'ORDINAL_POSITION' => '5'
                   },
                   '_client_name' => {
                       'ATTR_VALUE'       => 'libmysql',
                       'PROCESSLIST_ID'   => '3',
                       'ATTR_NAME'        => '_client_name',
                       'ORDINAL_POSITION' => '1'
                   },
                   '_client_version' => {
                       'ATTR_VALUE'       => '5.6.24',
                       'PROCESSLIST_ID'   => '3',
                       'ATTR_NAME'        => '_client_version',
                       'ORDINAL_POSITION' => '7'
                   },
                   '_os' => {
                       'ATTR_VALUE'       => 'osx10.8',
                       'PROCESSLIST_ID'   => '3',
                       'ATTR_NAME'        => '_os',
                       'ORDINAL_POSITION' => '0'
                   },
                   '_pid' => {
                       'ATTR_VALUE'       => '59860',
                       'PROCESSLIST_ID'   => '3',
                       'ATTR_NAME'        => '_pid',
                       'ORDINAL_POSITION' => '2'
                   },
                   '_platform' => {
                       'ATTR_VALUE'       => 'x86_64',
                       'PROCESSLIST_ID'   => '3',
                       'ATTR_NAME'        => '_platform',
                       'ORDINAL_POSITION' => '4'
                   }
                 };

   Private MetaData Methods
       ListDBs
               my $drh = DBI->install_driver("mysql");
               @dbs = $drh->func("$hostname:$port", '_ListDBs');
               @dbs = $drh->func($hostname, $port, '_ListDBs');
               @dbs = $dbh->func('_ListDBs');

           Returns a list of all databases managed by the MySQL server running on $hostname, port
           $port. This is a legacy method.  Instead, you should use the portable method

               @dbs = DBI->data_sources("mysql");

DATABASE HANDLES

       The DBD::mysql driver supports the following attributes of database handles (read only):

         $errno = $dbh->{'mysql_errno'};
         $error = $dbh->{'mysql_error'};
         $info = $dbh->{'mysql_hostinfo'};
         $info = $dbh->{'mysql_info'};
         $insertid = $dbh->{'mysql_insertid'};
         $info = $dbh->{'mysql_protoinfo'};
         $info = $dbh->{'mysql_serverinfo'};
         $info = $dbh->{'mysql_stat'};
         $threadId = $dbh->{'mysql_thread_id'};

       These correspond to mysql_errno(), mysql_error(), mysql_get_host_info(), mysql_info(),
       mysql_insert_id(), mysql_get_proto_info(), mysql_get_server_info(), mysql_stat() and
       mysql_thread_id(), respectively.

       mysql_clientinfo
         List information of the MySQL client library that DBD::mysql was built against:

           print "$dbh->{mysql_clientinfo}\n";

           5.2.0-MariaDB

       mysql_clientversion
           print "$dbh->{mysql_clientversion}\n";

           50200

       mysql_serverversion
           print "$dbh->{mysql_serverversion}\n";

           50200

       mysql_dbd_stats
           $info_hashref = $dbh->{mysql_dbd_stats};

         DBD::mysql keeps track of some statistics in the mysql_dbd_stats attribute.  The
         following stats are being maintained:

         auto_reconnects_ok
                 The number of times that DBD::mysql successfully reconnected to the mysql
                 server.

         auto_reconnects_failed
                 The number of times that DBD::mysql tried to reconnect to mysql but failed.

       The DBD::mysql driver also supports the following attributes of database handles
       (read/write):

       mysql_auto_reconnect
           This attribute determines whether DBD::mysql will automatically reconnect to mysql if
           the connection be lost. This feature defaults to off; however, if either the
           GATEWAY_INTERFACE or MOD_PERL environment variable is set, DBD::mysql will turn
           mysql_auto_reconnect on.  Setting mysql_auto_reconnect to on is not advised if 'lock
           tables' is used because if DBD::mysql reconnect to mysql all table locks will be lost.
           This attribute is ignored when AutoCommit is turned off, and when AutoCommit is turned
           off, DBD::mysql will not automatically reconnect to the server.

           It is also possible to set the default value of the "mysql_auto_reconnect" attribute
           for the $dbh by passing it in the "\%attr" hash for "DBI-"connect>.

             $dbh->{mysql_auto_reconnect} = 1;

           or

             my $dbh = DBI->connect($dsn, $user, $password, {
                mysql_auto_reconnect => 1,
             });

           Note that if you are using a module or framework that performs reconnections for you
           (for example DBIx::Connector in fixup mode), this value must be set to 0.

       mysql_use_result
           This attribute forces the driver to use mysql_use_result rather than
           mysql_store_result.  The former is faster and less memory consuming, but tends to
           block other processes.  mysql_store_result is the default due to that fact storing the
           result is expected behavior with most applications.

           It is possible to set the default value of the "mysql_use_result" attribute for the
           $dbh via the DSN:

             $dbh = DBI->connect("DBI:mysql:test;mysql_use_result=1", "root", "");

           You can also set it after creation of the database handle:

              $dbh->{mysql_use_result} = 0; # disable
              $dbh->{mysql_use_result} = 1; # enable

           You can also set or unset the "mysql_use_result" setting on your statement handle,
           when creating the statement handle or after it has been created.  See "STATEMENT
           HANDLES".

       mysql_enable_utf8
           This attribute determines whether DBD::mysql should assume strings stored in the
           database are utf8.  This feature defaults to off.

           When set, a data retrieved from a textual column type (char, varchar, etc) will have
           the UTF-8 flag turned on if necessary.  This enables character semantics on that
           string.  You will also need to ensure that your database / table / column is
           configured to use UTF8. See for more information the chapter on character set support
           in the MySQL manual: <http://dev.mysql.com/doc/refman/5.7/en/charset.html>

           Additionally, turning on this flag tells MySQL that incoming data should be treated as
           UTF-8.  This will only take effect if used as part of the call to connect().  If you
           turn the flag on after connecting, you will need to issue the command "SET NAMES utf8"
           to get the same effect.

       mysql_enable_utf8mb4
           This is similar to mysql_enable_utf8, but is capable of handling 4-byte UTF-8
           characters.

       mysql_bind_type_guessing
           This attribute causes the driver (emulated prepare statements) to attempt to guess if
           a value being bound is a numeric value, and if so, doesn't quote the value.  This was
           created by Dragonchild and is one way to deal with the performance issue of using
           quotes in a statement that is inserting or updating a large numeric value. This was
           previously called "unsafe_bind_type_guessing" because it is experimental. I have
           successfully run the full test suite with this option turned on, the name can now be
           simply "mysql_bind_type_guessing".

           CAVEAT: Even though you can insert an integer value into a character column, if this
           column is indexed, if you query that column with the integer value not being quoted,
           it will not use the index:

               MariaDB [test]> explain select * from test where value0 = '3' \G
               *************************** 1. row ***************************
                          id: 1
                 select_type: SIMPLE
                       table: test
                        type: ref
               possible_keys: value0
                         key: value0
                     key_len: 13
                         ref: const
                        rows: 1
                       Extra: Using index condition
               1 row in set (0.00 sec)

               MariaDB [test]> explain select * from test where value0 = 3
                   -> \G
               *************************** 1. row ***************************
                          id: 1
                 select_type: SIMPLE
                       table: test
                        type: ALL
               possible_keys: value0
                         key: NULL
                     key_len: NULL
                         ref: NULL
                        rows: 6
                       Extra: Using where
               1 row in set (0.00 sec)

           See bug: https://rt.cpan.org/Ticket/Display.html?id=43822

           "mysql_bind_type_guessing" can be turned on via

            - through DSN

             my $dbh= DBI->connect('DBI:mysql:test', 'username', 'pass',
             { mysql_bind_type_guessing => 1})

             - OR after handle creation

             $dbh->{mysql_bind_type_guessing} = 1;

       mysql_bind_comment_placeholders
           This attribute causes the driver (emulated prepare statements) will cause any
           placeholders in comments to be bound. This is not correct prepared statement behavior,
           but some developers have come to depend on this behavior, so I have made it available
           in 4.015

       mysql_no_autocommit_cmd
           This attribute causes the driver to not issue 'set autocommit' either through explicit
           or using mysql_autocommit(). This is particularly useful in the case of using MySQL
           Proxy.

           See the bug report:

           https://rt.cpan.org/Public/Bug/Display.html?id=46308

           "mysql_no_autocommit_cmd" can be turned on when creating the database handle:

             my $dbh = DBI->connect('DBI:mysql:test', 'username', 'pass',
             { mysql_no_autocommit_cmd => 1});

           or using an existing database handle:

             $dbh->{mysql_no_autocommit_cmd} = 1;

       ping
           This can be used to send a ping to the server.

             $rc = $dbh->ping();

STATEMENT HANDLES

       The statement handles of DBD::mysql support a number of attributes. You access these by
       using, for example,

         my $numFields = $sth->{NUM_OF_FIELDS};

       Note, that most attributes are valid only after a successful execute.  An "undef" value
       will returned otherwise. The most important exception is the "mysql_use_result" attribute,
       which forces the driver to use mysql_use_result rather than mysql_store_result. The former
       is faster and less memory consuming, but tends to block other processes. (That's why
       mysql_store_result is the default.)

       To set the "mysql_use_result" attribute, use either of the following:

         my $sth = $dbh->prepare("QUERY", { mysql_use_result => 1});

       or

         my $sth = $dbh->prepare($sql);
         $sth->{mysql_use_result} = 1;

       Column dependent attributes, for example NAME, the column names, are returned as a
       reference to an array. The array indices are corresponding to the indices of the arrays
       returned by fetchrow and similar methods. For example the following code will print a
       header of table names together with all rows:

         my $sth = $dbh->prepare("SELECT * FROM $table") ||
           die "Error:" . $dbh->errstr . "\n";

         $sth->execute ||  die "Error:" . $sth->errstr . "\n";

         my $names = $sth->{NAME};
         my $numFields = $sth->{'NUM_OF_FIELDS'} - 1;
         for my $i ( 0..$numFields ) {
             printf("%s%s", $i ? "," : "", $$names[$i]);
         }
         print "\n";
         while (my $ref = $sth->fetchrow_arrayref) {
             for my $i ( 0..$numFields ) {
             printf("%s%s", $i ? "," : "", $$ref[$i]);
             }
             print "\n";
         }

       For portable applications you should restrict yourself to attributes with capitalized or
       mixed case names. Lower case attribute names are private to DBD::mysql. The attribute list
       includes:

       ChopBlanks
           this attribute determines whether a fetchrow will chop preceding and trailing blanks
           off the column values. Chopping blanks does not have impact on the max_length
           attribute.

       mysql_gtids
           Returns GTID(s) if GTID session tracking is ensabled in the server via
           session_track_gtids.

       mysql_insertid
           If the statement you executed performs an INSERT, and there is an AUTO_INCREMENT
           column in the table you inserted in, this attribute holds the value stored into the
           AUTO_INCREMENT column, if that value is automatically generated, by storing NULL or 0
           or was specified as an explicit value.

           Typically, you'd access the value via $sth->{mysql_insertid}. The value can also be
           accessed via $dbh->{mysql_insertid} but this can easily produce incorrect results in
           case one database handle is shared.

       mysql_is_blob
           Reference to an array of boolean values; TRUE indicates, that the respective column is
           a blob. This attribute is valid for MySQL only.

       mysql_is_key
           Reference to an array of boolean values; TRUE indicates, that the respective column is
           a key. This is valid for MySQL only.

       mysql_is_num
           Reference to an array of boolean values; TRUE indicates, that the respective column
           contains numeric values.

       mysql_is_pri_key
           Reference to an array of boolean values; TRUE indicates, that the respective column is
           a primary key.

       mysql_is_auto_increment
           Reference to an array of boolean values; TRUE indicates that the respective column is
           an AUTO_INCREMENT column.  This is only valid for MySQL.

       mysql_length
       mysql_max_length
           A reference to an array of maximum column sizes. The max_length is the maximum
           physically present in the result table, length gives the theoretically possible
           maximum. max_length is valid for MySQL only.

       NAME
           A reference to an array of column names.

       NULLABLE
           A reference to an array of boolean values; TRUE indicates that this column may contain
           NULL's.

       NUM_OF_FIELDS
           Number of fields returned by a SELECT or LISTFIELDS statement.  You may use this for
           checking whether a statement returned a result: A zero value indicates a non-SELECT
           statement like INSERT, DELETE or UPDATE.

       mysql_table
           A reference to an array of table names, useful in a JOIN result.

       TYPE
           A reference to an array of column types. The engine's native column types are mapped
           to portable types like DBI::SQL_INTEGER() or DBI::SQL_VARCHAR(), as good as possible.
           Not all native types have a meaningful equivalent, for example
           DBD::mysql::FIELD_TYPE_INTERVAL is mapped to DBI::SQL_VARCHAR().  If you need the
           native column types, use mysql_type. See below.

       mysql_type
           A reference to an array of MySQL's native column types, for example
           DBD::mysql::FIELD_TYPE_SHORT() or DBD::mysql::FIELD_TYPE_STRING().  Use the TYPE
           attribute, if you want portable types like DBI::SQL_SMALLINT() or DBI::SQL_VARCHAR().

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

       mysql_warning_count
           The number of warnings generated during execution of the SQL statement.  This
           attribute is available on both statement handles and database handles.

TRANSACTION SUPPORT

       The transaction support works as follows:

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

       •   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.

       •   The methods

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

           will issue the commands ROLLBACK and COMMIT, 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.

       Given the above, you should note the following:

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

       •   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!
             }

       •   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.

       •   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.

       •   The "reconnect" feature of DBD::mysql can be toggled by using the 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.

MULTIPLE RESULT SETS

       DBD::mysql supports multiple result sets, thanks to Guy Harrison!

       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 someproc() 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}-1) {
             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)

   Issues with multiple result sets
       Please be aware there could be issues 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.

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 yes, since MySQL 5.5 it is.

ASYNCHRONOUS QUERIES

       You can make a single asynchronous query per MySQL connection; this allows you to submit a
       long-running query to the server and have an event loop inform you when it's ready.  An
       asynchronous query is started by either setting the 'async' attribute to a true value in
       the "do" in DBI method, or in the "prepare" in DBI method.  Statements created with
       'async' set to true in prepare always run their queries asynchronously when "execute" in
       DBI is called.  The driver also offers three additional methods: "mysql_async_result",
       "mysql_async_ready", and "mysql_fd".  "mysql_async_result" returns what do or execute
       would have; that is, the number of rows affected.  "mysql_async_ready" returns true if
       "mysql_async_result" will not block, and zero otherwise.  They both return "undef" if that
       handle was not created with 'async' set to true or if an asynchronous query was not
       started yet.  "mysql_fd" returns the file descriptor number for the MySQL connection; you
       can use this in an event loop.

       Here's an example of how to use the asynchronous query interface:

         use feature 'say';
         $dbh->do('SELECT SLEEP(10)', { async => 1 });
         until($dbh->mysql_async_ready) {
           say 'not ready yet!';
           sleep 1;
         }
         my $rows = $dbh->mysql_async_result;

INSTALLATION

       See DBD::mysql::INSTALL.

AUTHORS

       Originally, there was a non-DBI driver, Mysql, which was much like PHP drivers such as
       mysql and mysqli. The Mysql module was originally written by Andreas König
       <koenig@kulturbox.de> who still, to this day, contributes patches to DBD::mysql. An
       emulated version of Mysql was provided to DBD::mysql from Jochen Wiedmann, but eventually
       deprecated as it was another bundle of code to maintain.

       The first incarnation of DBD::mysql was developed by Alligator Descartes, who was also
       aided and abetted by Gary Shea, Andreas König and Tim Bunce.

       The current incarnation of DBD::mysql was written by Jochen Wiedmann, then numerous
       changes and bug-fixes were added by Rudy Lippan. Next, prepared statement support was
       added by Patrick Galbraith and Alexy Stroganov (who also solely added embedded server
       support).

       For the past nine years DBD::mysql has been maintained by Patrick Galbraith
       (patg@patg.net), and recently with the great help of Michiel Beijen
       (michiel.beijen@gmail.com),  along with the entire community of Perl developers who keep
       sending patches to help continue improving DBD::mysql

CONTRIBUTIONS

       Anyone who desires to contribute to this project is encouraged to do so.  Currently, the
       source code for this project can be found at Github:

       <https://github.com/perl5-dbi/DBD-mysql/>

       Either fork this repository and produce a branch with your changeset that the maintainer
       can merge to his tree, or create a diff with git. The maintainer is more than glad to take
       contributions from the community as many features and fixes from DBD::mysql have come from
       the community.

COPYRIGHT

       This module is

       •   Large Portions Copyright (c) 2004-2013 Patrick Galbraith

       •   Large Portions Copyright (c) 2004-2006 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

LICENSE

       This module is released under the same license as Perl itself. See
       <http://www.perl.com/perl/misc/Artistic.html> for details.

MAILING LIST SUPPORT

       This module is maintained and supported on a mailing list, dbi-users.

       To subscribe to this list, send an email to

       dbi-users-subscribe@perl.org

       Mailing list archives are at

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

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

       Information on DBD::mysql specifically can be gained by typing:

           perldoc DBD::mysql

       (this will display the document you're currently reading)

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:

       <https://rt.cpan.org/Dist/Display.html?Name=DBD-mysql>

       Note: until recently, MySQL/Sun/Oracle responded to bugs and assisted in fixing bugs which
       many thanks should be given for their help!  This driver is outside the realm of the
       numerous components they support, and the maintainer and community solely support
       DBD::mysql