public function orderBy(array $columns_and_direction) {
		// for each given parameter
		foreach($columns_and_direction as $column => $direction) {
			// if the direction is not valid force ASC
			$direction == 'ASC' || $direction == 'DESC' ?: $direction = 'ASC';
			// secure the column name
			list($column) = Query\Convert::columnToPlaceholder($this->Quote ,$column);
			// push it
			$this->Order[] = "{$column} $direction";
		}
		// return self to the next method
		return $this;
	}