Provided by: libdbd-mysql-perl_4.050-5_amd64 
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
Enables (TRUE value) or disables (FALSE value) the flag CLIENT_FOUND_ROWS while
connecting to the MySQL server. This has a somewhat funny effect: Without
mysql_client_found_rows, if you perform a query like
UPDATE $table SET id = 1 WHERE id = 1;
then the MySQL engine will always return 0, because no rows have changed. With
mysql_client_found_rows however, it will return the number of rows that have an id
1, as some people are expecting. (At least for compatibility to other engines.)
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