NAME

       MQdb::Database - Generalized handle on an DBI database handle

DESCRIPTION

       Generalized handle on an DBI database handle. Used to provide an instance which holds
       connection information and allows a higher level get_connection/ disconnect logic that
       persists above the specific DBI connections. Also provides a real object for use with the
       rest of the toolkit.

SUMMARY

       MQdb::Database provides the foundation of the MappedQuery system.  Databases are primarily
       specified with a URL format.  The URL format includes specification of a driver so this
       single method can select among the supported DBD drivers.  Currently the system supports
       MYSQL, Oracle, and SQLite.  The URL also allows the system to provide the foundation for
       doing federation of persisted objects.  Each DBObject contains a pointer to the Database
       instance where it is stored.  With the database URL and internal database ID, each object
       is defined in a global space.

       Attributes of MQdb::Database
         driver   :  mysql, oracle, sqlite (default mysql)
         user     :  username if the database requires
         password :  password if the database requires
         host     :  hostname of the database server machine
         port     :  IP port of the database if required
                     (mysql default is 3306)
         dbname   :  database/schema name on the database server
                     for sqlite, this is the database file

       Example URLS
         mysql://<user>:<pass>@<host>:<port>/<database_name>
         mysql://<host>:<port>/<database_name>
         mysql://<user>@<host>:<port>/<database_name>
         mysql://<host>/<database_name>
         oracle://<user>:<pass>@/<database_name>
         oracle://<user>:<pass>@<host>:<port>/<database_name>
         sqlite:///<database_file>

CONTACT

       Jessica Severin <jessica.severin@gmail.com>

LICENSE

        * Software License Agreement (BSD License)
        * MappedQueryDB [MQdb] toolkit
        * copyright (c) 2006-2009 Jessica Severin
        * All rights reserved.
        * Redistribution and use in source and binary forms, with or without
        * modification, are permitted provided that the following conditions are met:
        *     * Redistributions of source code must retain the above copyright
        *       notice, this list of conditions and the following disclaimer.
        *     * Redistributions in binary form must reproduce the above copyright
        *       notice, this list of conditions and the following disclaimer in the
        *       documentation and/or other materials provided with the distribution.
        *     * Neither the name of Jessica Severin nor the
        *       names of its contributors may be used to endorse or promote products
        *       derived from this software without specific prior written permission.
        *
        * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
        * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
        * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
        * DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDERS BE LIABLE FOR ANY
        * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
        * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
        * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
        * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
        * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
        * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

APPENDIX

       The rest of the documentation details each of the object methods. Internal methods are
       usually preceded with a _

   new
         Description: instance creation method
         Parameter  : a hash reference of options same as attribute methods
         Returntype : instance of this Class (subclass)
         Exceptions : none

   new
         Description: instance creation method
         Returntype : instance of this Class (subclass)
         Exceptions : none

   init
         Description: initialization method which subclasses can extend
         Returntype : $self
         Exceptions : subclass dependent

   new_from_url
         Description: primary instance creation method
         Parameter  : a string in URL format
         Returntype : instance of MQdb::Database
         Examples   : my $db = MQdb::Database->new_from_url("mysql://<user>:<pass>@<host>:<port>/<database_name>");
                      e.g. mysql://<host>:<port>/<database_name>
                      e.g. mysql://<user>@<host>:<port>/<database_name>
                      e.g. mysql://<host>/<database_name>
                      e.g. sqlite:///<database_file>
         my $class = shift;
         Exceptions : none

   copy
         Description: makes a copy of the database configuration.
                      New instance will have its own database connection
         Returntype : instance of MQdb::Database

   dbc
         Description: connects to database and returns a DBI connection
         Returntype : DBI database handle
         Exceptions : none

   disconnect
         Description: disconnects handle from database, but retains object and
                      all information so that it can be reconnected again
                      at a later time.
         Returntype : none
         Exceptions : none

   full_url
         Description: returns the URL of this database with user and password
         Returntype : string
         Exceptions : none

   url
         Description: returns URL of this database but without user:password
                      used for global referencing and federation systems
         Returntype : string
         Exceptions : none

   xml
         Description: returns XML of this database but without user:password
                      used for global referencing and federation systems
         Returntype : string
         Exceptions : none

   execute_sql
         Description    : executes SQL statement with external parameters and placeholders
         Example        : $db->execute_sql("insert into table1(id, value) values(?,?)", $id, $value);
         Parameter[1]   : sql statement string
         Parameter[2..] : optional parameters for the SQL statement
         Returntype     : none
         Exceptions     : none

   do_sql
         Description    : executes SQL statement with "do" and no external parameters
         Example        : $db->do_sql("insert into table1(id, value) values(null,'hello world');");
         Parameter      : sql statement string with no external parameters
         Returntype     : none
         Exceptions     : none

   fetch_col_value
         Arg (1)    : $sql (string of SQL statement with place holders)
         Arg (2...) : optional parameters to map to the placehodlers within the SQL
         Example    : $value = $self->fetch_col_value($db, "select some_column from my_table where id=?", $id);
         Description: General purpose function to allow fetching of a single column from a single row.
         Returntype : scalar value
         Exceptions : none
         Caller     : within subclasses to easy development