Magento. The right way to alter table (add column) via upgrade script

mage_right_way_to_alter_table_via_upgrade_script.md

Right way to alter table (add column) via upgrade script

Add new text column(if it not existed) with name yt_id in table with alias aboutus/aboutus defined in config.xml

/* @var $installer Mage_Core_Model_Resource_Setup */
$installer    = $this;
$aboutusTable = $installer->getTable('aboutus/aboutus');
$connection   = $installer->getConnection();

$installer->startSetup();

$exists = $connection->tableColumnExists($aboutusTable, 'yt_id');

if(!$exists){
    $connection->addColumn(
        $aboutusTable,
        'yt_id',
        array(
            'type'     => Varien_Db_Ddl_Table::TYPE_TEXT,
            'comment'  => 'Youtube video identifier',
            'nullable'  => true
        )
    );
}

$installer->endSetup();