Magento : Create an external database connection

Add the following code  to your config.xml under global tag

Consider Bd_test module

<global>

        <resources>

            <test_write>

                <connection>

                    <use>test_database</use>

                </connection>

            </test_write>

            <test_read>

                <connection>

                    <use>test_database</use>

                </connection>

            </test_read>

            <test_setup>

                <connection>

                    <use>core_setup</use>

                </connection>

            </test_setup>

            <test_database>

                <connection>

                    <host><![CDATA[localhost]]></host>

                    <username><![CDATA[db_username]]></username>

                    <password><![CDATA[db_password]]></password>

                    <dbname><![CDATA[db_name]]></dbname>

                    <model>mysql4</model>

                    <type>pdo_mysql</type>

                    <active>1</active>

                </connection>

            </test_database>

        </resources>

    </global>


Get data

    $resource   = Mage::getSingleton('core/resource');

    $conn       = $resource->getConnection('test_read');

    $results    = $conn->query('SELECT * FROM TableName');

    print_r($results)