Provided by: libdbd-mysql-perl_4.033-1ubuntu0.1_amd64 
NAME
DBD::mysql - MySQL driver for the Perl5 Database Interface (DBI)
SYNOPSIS
use DBI;
$dsn = "DBI:mysql:database=$database;host=$hostname;port=$port";
$dbh = DBI->connect($dsn, $user, $password);
$drh = DBI->install_driver("mysql");
@databases = DBI->data_sources("mysql");
or
@databases = DBI->data_sources("mysql",
{"host" => $host, "port" => $port, "user" => $user, password => $pass});
$sth = $dbh->prepare("SELECT * FROM foo WHERE bla");
or
$sth = $dbh->prepare("LISTFIELDS $table");
or
$sth = $dbh->prepare("LISTINDEX $table $index");
$sth->execute;
$numRows = $sth->rows;
$numFields = $sth->{'NUM_OF_FIELDS'};
$sth->finish;
$rc = $drh->func('createdb', $database, $host, $user, $password, 'admin');
$rc = $drh->func('dropdb', $database, $host, $user, $password, 'admin');
$rc = $drh->func('shutdown', $host, $user, $password, 'admin');
$rc = $drh->func('reload', $host, $user, $password, 'admin');
$rc = $dbh->func('createdb', $database, 'admin');
$rc = $dbh->func('dropdb', $database, 'admin');
$rc = $dbh->func('shutdown', 'admin');
$rc = $dbh->func('reload', 'admin');
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);
A "database" must always be specified.
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).
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 database:
mysql_ssl=1
This means that your communication with the server will be encrypted.
If you turn mysql_ssl on, you might also wish to use the following flags:
mysql_ssl_client_key
mysql_ssl_client_cert
mysql_ssl_ca_file
mysql_ssl_ca_path
mysql_ssl_cipher
These are used to specify the respective parameters of a call to mysql_ssl_set, if mysql_ssl is
turned on.
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.
Prepared statement support (server side prepare)
As of 3.0002_1, server side prepare statements were on by default (if your server was >= 4.1.3).
As of 3.0009, they were off by default again due to issues with the prepared statement API (all
other mysql connectors are set this way until C API issues are resolved). The requirement to use
prepared statements still remains that you have a server >= 4.1.3
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 }
);
* Note: delimiter for this param is ';'
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
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");
Server Administration
admin
$rc = $drh->func("createdb", $dbname, [host, user, password,], 'admin');
$rc = $drh->func("dropdb", $dbname, [host, user, password,], 'admin');
$rc = $drh->func("shutdown", [host, user, password,], 'admin');
$rc = $drh->func("reload", [host, user, password,], 'admin');
or
$rc = $dbh->func("createdb", $dbname, 'admin');
$rc = $dbh->func("dropdb", $dbname, 'admin');
$rc = $dbh->func("shutdown", 'admin');
$rc = $dbh->func("reload", 'admin');
For server administration you need a server connection. For obtaining this connection you have two
options: Either use a driver handle (drh) and supply the appropriate arguments (host, defaults
localhost, user, defaults to '' and password, defaults to ''). A driver handle can be obtained with
$drh = DBI->install_driver('mysql');
Otherwise reuse the existing connection of a database handle (dbh).
There's only one function available for administrative purposes, comparable to the mysqladmin
programs. The command being execute depends on the first argument:
createdb
Creates the database $dbname. Equivalent to "mysqladmin create $dbname".
dropdb
Drops the database $dbname. Equivalent to "mysqladmin drop $dbname".
It should be noted that database deletion is not prompted for in any way. Nor is it undo-able
from DBI.
Once you issue the dropDB() method, the database will be gone!
These method should be used at your own risk.
shutdown
Silently shuts down the database engine. (Without prompting!) Equivalent to "mysqladmin
shutdown".
reload
Reloads the servers configuration files and/or tables. This can be particularly important if you
modify access privileges or create new users.
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 = $dhb->{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 Chapter 10 of the mysql
manual for details.
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.
This option is experimental and may change in future versions.
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;
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_insertid
MySQL has the ability to choose unique key values automatically. If this happened, the new ID will be
stored in this attribute. An alternative way for accessing this attribute is via
$dbh->{'mysql_insertid'}. (Note we are using the $dbh in this case!)
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)
For more examples, please see the eg/ directory. This is where helpful DBD::mysql code snippets will be
added in the future.
Issues with multiple result sets
Please be aware ther 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 "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 How to
make a threadsafe client in the manual.
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 is not
currently running an asynchronous query. "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
perl v5.22.1 2016-10-13 DBD::mysql(3pm)