magento: insert query for a custom table

$connection = Mage::getSingleton('core/resource')->getConnection('core_write');
    $connection->beginTransaction();

    $sql = 'INSERT INTO tableName (`field1`, `field2`) VALUES (?, ?)';
    $bind = array('value1', 'value2');
    $connection->query($sql, $bind);
    $connection->commit();