/**
* Start a SQL transaction
*
* Some examples of different ways to use transactions:
*
*
*
* // 1) Example using the xdatabase Query class
* try
* {
* Query::begin();
* Query::sql($sql)->execute();
* // ... more code/queries
* Query::commit();
* }
* catch (Exception $e)
* {
* Query::rollback();
* }
*
* // 2) Example using existing Kohana style
* try
* {
* $db = Database::instance();
* $db->begin();
* DB::query(Database::INSERT, $sql)->execute($db);
* // ... more code/queries
* $db->commit();
* }
* catch (Exception $e)
* {
* $db->rollback();
* }
*
* // 3) Example using the Query class without the default database
* $db = Database::instance('alternate');
* Query::begin($db);
* Query::sql($sql)->execute($db);
* // ... more code/queries
* // If some conditions met:
* Query::commit($db);
* // Else
* Query::rollback($db);
*
* @return boolean
*/
public static function begin($db = NULL)
{
$query = new Database_Query(NULL, NULL);
return $query->begin($db);
}