/ 
Msql-Mysql-modules-1.1833
River stage zero No dependents
/ DBD::mysql

NAME

DBD::mSQL / DBD::mysql - mSQL and mysql drivers for the Perl5 Database Interface (DBI)

SYNOPSIS

    use DBI;

    $dbh = DBI->connect("DBI:mSQL:$database:$hostname:$port",
			undef, undef);

        or

    $dsn = "DBI:mysql:$database:$hostname:$port";
    if ($compression) { $dsn .= ";mysql_compression=1"; }
    $dbh = DBI->connect($dsn, $user, $password);

    @databases = DBD::mysql::dr->func( $hostname, '_ListDBs' );
    @tables = $dbh->func( '_ListTables' );

    $sth = $dbh->prepare("LISTFIELDS $table");
    $sth->execute;
    $sth->finish;

    $sth = $dbh->prepare("SELECT * FROM foo WHERE bla");
    $sth->execute;
    $numRows = $sth->rows;
    $numFields = $sth->{'NUM_OF_FIELDS'};
    $sth->finish;

    $rc = $drh->func( $database, '_CreateDB' );
    $rc = $drh->func( $host, $database, '_CreateDB' );
    $rc = $drh->func( $database, '_DropDB' );
    $rc = $drh->func( $host, $database, '_DropDB' );

DESCRIPTION

<DBD::mysql> and <DBD::mSQL> are the Perl5 Database Interface drivers for the mysql, mSQL 1.x and mSQL 2.x databases. The drivers are part of the mysql-modules and Msql-modules packages, respectively.

Class Methods

connect
    use DBI;

    $dbh = DBI->connect("DBI:mSQL:$database", undef, undef);
    $dbh = DBI->connect("DBI:mSQL:$database:$hostname", undef, undef);
    $dbh = DBI->connect("DBI:mSQL:$database:$hostname:$port",
			undef, undef);

        or

    use DBI;

    $dsn = "DBI:mysql:$database";
    $dsn = "DBI:mysql:$database:$hostname";
    $dsn = "DBI:mysql:$database:$hostname:$port";
    $dsn = "DBI:mysql:$database:$hostname:$port;mysql_compression=1";

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

A database must always be specified.

The hostname, if not specified or specified as '', will default to an mysql or mSQL daemon running on the local machine on the default port for the UNIX socket.

Should the mysql or mSQL daemon 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.

As of MySQL 3.22.3, a new feature is supported: If you finish your DSN with ";mysql_compression=1", then the communication between client and server will be compressed.

Private MetaData Methods

ListDBs
@dbs = $dbh->func("$hostname:$port", '_ListDBs');

Returns a list of all databases managed by the mysql daemon or mSQL daemon running on $hostname, port $port. This method is rarely needed for databases running on localhost: You should use the portable method

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

    or

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

whenever possible. It is a design problem of this method, that there's no way of supplying a host name or port number to data_sources, that's the only reason why we still support ListDBs. :-(

ListTables
@tables = $dbh->func('_ListTables');

Once connected to the desired database on the desired mysql or mSQL mSQL daemon with the DBI-connect()> method, we may extract a list of the tables that have been created within that database.

ListTables returns an array containing the names of all the tables present within the selected database. If no tables have been created, an empty list is returned.

@tables = $dbh->func( '_ListTables' );
foreach $table ( @tables ) {
    print "Table: $table\n";
  }
ListFields

Deprecated, see "COMPATIBILITY ALERT" below.

ListSelectedFields

Deprecated, see "COMPATIBILITY ALERT" below.

Database Manipulation

CreateDB
DropDB
$rc = $drh->func( $database, '_CreateDB' );
$rc = $drh->func( $database, '_DropDB' );

  or

$rc = $drh->func( $host, $database, '_CreateDB' );
$rc = $drh->func( $host, $database, '_DropDB' );

These two methods allow programmers to create and drop databases from DBI scripts. Since mSQL disallows the creation and deletion of databases over the network, these methods explicitly connect to the mSQL daemon running on the machine localhost and execute these operations there.

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 methods should be used at your own risk.

DATABASE HANDLES

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

$infoString = $dbh->{'info'};
$threadId = $dbh->{'thread_id'};

These correspond to mysql_info() and mysql_tread_id(), respectively.

STATEMENT HANDLES

The statement handles of DBD::mysql and DBD::mSQL 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 successfull execute. An undef value will returned in that case. The most important exception is the mysql_use_result attribute: This 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("QUERY");
$sth->{"mysql_use_result"} = 1;

Of course it doesn't make sense to set this attribute before calling the execute method.

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 $table");
  if (!$sth) {
      die "Error:" . $dbh->errstr . "\n";
  }
  if (!$sth->execute) {
      die "Error:" . $sth->errstr . "\n";
  }
  my $names = $sth->{'NAME'};
  my $numFields = $sth->{'NUM_OF_FIELDS'};
  for (my $i = 0;  $i < $numFields;  $i++) {
      printf("%s%s", $$names[$i], $i ? "," : "");
  }
  print "\n";
  while (my $ref = $sth->fetchrow_arrayref) {
      for (my $i = 0;  $i < $numFields;  $i++) {
	  printf("%s%s", $$ref[$i], $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::mSQL and 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.

insertid

MySQL has the ability to choose unique key values automatically. If this happened, the new ID will be stored in this attribute. This attribute is not valid for DBD::mSQL.

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.

is_key

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

is_num

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

is_pri_key

Reference to an array of boolean values; TRUE indicates, that the respective column is a primary key. This is only valid for MySQL and mSQL 1.0.x: mSQL 2.x uses indices.

is_not_null

A reference to an array of boolean values; FALSE indicates that this column may contain NULL's. You should better use the NULLABLE attribute above which is a DBI standard.

length
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.

table

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

type

A reference to an array of column types. It depends on the DBMS, which values are returned, even for identical types. mSQL will return types like &DBD::mSQL::INT_TYPE, &DBD::msql::TEXT_TYPE etc., MySQL uses &DBD::mysql::FIELD_TYPE_SHORT, &DBD::mysql::FIELD_TYPE_STRING etc.

COMPATIBILITY ALERT

As of version 0.70 DBD::mSQL has a new maintainer. Even more, the sources have been completely rewritten in August 1997, so it seemed apropriate to bump the version number: Incompatibilities are more than likely.

Recent changes:

New connect method

DBD::mSQL and DBD::mysql now use the new connect method as introduced with DBI 0.83 or so. For compatibility reasons the old method still works, but the driver issues a warning when he detects use of the old version. There's no workaround, you must update your sources. (Sorry, but the change was in DBI, not in DBD::mysql and DBD::mSQL.)

_ListFields returning statement handle

As of Msql-modules 1.1805, the private functions

$dbh->func($table, "_ListFields");

and

$sth->func("_ListSelectedFields");

no longer return a simple hash, but a statement handle. (_ListSelectedFields is a stub now which just returns $self.) This should usually not be visible, when your statement handle gets out of scope. However, if your database handle ($dbh in the above example) disconnects, either because you explicitly disconnect or because he gets out of scope, and the statement handle is still active, DBI will issue a warning for active cursors being destroyed.

The simple workaround is to execute $sth->finish or to ensure that $sth gets out of scope before $dbh. Sorry, but it was obvious nonsense to support two different things for accessing the basically same thing: A M(y)SQL result.

The drivers do not conform to the current DBI specification in some minor points. For example, the private attributes is_num or is_blob have been written IS_NUM and IS_BLOB. For historical reasons we continue supporting the capitalized names, although the DBI specification now reserves capitalized names for standard names, mixed case for DBI and lower case for private attributes and methods.

We currently consider anything not conforming to the DBI as deprecated. It is quite possible that we remove support of these deprecated names and methods in the future. In particular these includes:

$sth->func($table, '_ListSelectedFields')

highly deprecated, all attributes are directly accessible via the statement handle. For example instead of

$ref = $sth->func($table, '_ListSelectedFields')
my @names = $ref->{'NAME'}

you just do a

my @names = @{$sth->{'NAME'}};
Capitalized attribute names

Deprecated, should be replaced by the respective lower case names.

MULTITHREADING

The multithreading capabilities of the Msql-Mysql-modules 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::mSQL and DBD::mysql are completely thread safe, if the C libraries thread safe and you don't share handles among threads.

The obvious questions is: Are the C libraries thread safe? In the case of mSQL the answer is definitely "no". The C library has a concept of one single active connection at a time and that is not what threads like.

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.

BUGS

The port part of the first argument to the connect call is implemented in an unsafe way when using mSQL. In fact it is just stting the environment variable MSQL_TCP_PORT during the connect call. If another connect call uses another port and the handles are used simultaneously, they will interfere. I doubt that this will ever change.

Please speak up now (June 1997) if you encounter additional bugs. I'm still learning about the DBI API and can neither judge the quality of the code presented here nor the DBI compliancy. But I'm intending to resolve things quickly as I'd really like to get rid of the multitude of implementations ASAP.

When running "make test", you will notice that some test scripts fail. This is due to bugs in the respective databases, not in the DBI drivers:

Nulls

mSQL seems to have problems with NULL's: The following fails with mSQL 2.0.1 running on a Linux 2.0.30 machine:

[joe@laptop Msql-modules-1.18]$ msql test
Welcome to the miniSQL monitor.  Type \h for help.
mSQL > CREATE TABLE foo (id INTEGER, name CHAR(6))\g
Query OK.  1 row(s) modified or retrieved.
mSQL > INSERT INTO foo VALUES (NULL, 'joe')\g
Query OK.  1 row(s) modified or retrieved.
mSQL > SELECT * FROM foo WHERE id = NULL\g
Query OK.  0 row(s) modified or retrieved.
+----------+------+
| id       | name |
+----------+------+
+----------+------+
mSQL >
Blanks

mysql has problems with Blanks on the right side of string fields: They get chopped of. (Tested with mysql 3.20.25 on a Linux 2.0.30 machine.)

[joe@laptop Msql-modules-1.18]$ mysql test
Welcome to the mysql monitor.  Commands ends with ; or \g.
Type 'help' for help.
mysql> CREATE TABLE foo (id INTEGER, bar CHAR(8));
Query OK, 0 rows affected (0.10 sec)
mysql> INSERT INTO foo VALUES (1, ' a b c ');
Query OK, 1 rows affected (0.00 sec)
mysql> SELECT * FROM foo;
1 rows in set (0.19 sec)
+------+--------+
| id   | bar    |
+------+--------+
|    1 |  a b c |
+------+--------+
mysql> quit;
[joe@laptop Msql-modules-1.18]$ mysqldump test foo

[deleted]

INSERT INTO foo VALUES (1,' a b c');

AUTHOR

DBD::mSQL has been primarily written by Alligator Descartes (descarte@hermetica.com), who has been aided and abetted by Gary Shea, Andreas Koenig and Tim Bunce amongst others. Apologies if your name isn't listed, it probably is in the file called 'Acknowledgments'. As of version 0.80 the maintainer is Andreas König. Version 2.00 is an almost complete rewrite by Jochen Wiedmann.

COPYRIGHT

This module is Copyright (c)1997 Jochen Wiedmann, with code portions Copyright (c)1994-1997 their original authors. This module is released under the 'Artistic' license which you can find in the perl distribution.

This document is Copyright (c)1997 Alligator Descartes. All rights reserved. Permission to distribute this document, in full or in part, via email, Usenet, ftp archives or http is granted providing that no charges are involved, reasonable attempt is made to use the most current version and all credits and copyright notices are retained ( the AUTHOR and COPYRIGHT sections ). Requests for other distribution rights, including incorporation into commercial products, such as books, magazine articles or CD-ROMs should be made to Alligator Descartes <descarte@hermetica.com>.

MAILING LIST SUPPORT

This module is maintained and supported on a mailing list,

msql-mysql-modules@tcx.se

To subscribe to this list, send a mail with the words

subscribe msql-mysql-modules

or

subscribe msql-mysql-modules-digest

in the first line of the body to mdomo@tcx.se. A mailing list archive is in preparation.

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

http://www.fugue.com/dbi

Mailing list archives are at

http://www.rosat.mpe-garching.mpg.de/mailing-lists/PerlDB-Interest/
http://outside.organic.com/mail-archives/dbi-users/
http://www.coe.missouri.edu/~faq/lists/dbi.html

ADDITIONAL DBI INFORMATION

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

http://www.hermetica.com/technologia/perl/DBI

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

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

perldoc DBI

right now!

1 POD Error

The following errors were encountered while parsing the POD:

Around line 676:

Non-ASCII character seen before =encoding in 'König.'. Assuming CP1252