/**
  * Execute the given SQL query.
  * This abstract function must be defined by subclasses as part of the actual implementation.
  * It should return a subclass of SS_Query as the result.
  *
  * @param string $sql The SQL query to execute
  * @param int $errorLevel The level of error reporting to enable for the query
  * @return Query
  */
 public function query($sql, $errorLevel = E_USER_ERROR)
 {
     return $this->database->query($sql, $errorLevel);
 }