next()) {
			if($column) {
				$result[] = $record[$column];
			} else {
				$result[] = $record[key($record)];
			}
		}
		return $result;
	}
	/**
	 * Return an array containing all values in the leftmost column, where the 
	 * keys are the same as the values.
	 *
	 * @return array
	 */
	public function keyedColumn() {
		$column = array();
		foreach($this as $record) {
			$val = $record[key($record)];
			$column[$val] = $val;
		}
		return $column;
	}
	/**
	 * Return a map from the first column to the second column.
	 *
	 * @return array
	 */
	public function map() {
		$column = array();
		foreach($this as $record) {
			$key = reset($record);
			$val = next($record);
			$column[$key] = $val;
		}
		return $column;
	}
	/**
	 * Returns the next record in the iterator.
	 *
	 * @return array
	 */
	public function record() {
		return $this->next();
	}
	/**
	 * Returns the first column of the first record.
	 *
	 * @return string
	 */
	public function value() {
		$record = $this->next();
		if($record) {
			return $record[key($record)];
		}
	}
	/**
	 * Return an HTML table containing the full result-set.
	 */
	public function table() {
		$first = true;
		$result = "
\n";
		
		foreach($this as $record) {
			if($first) {
				$result .= "";
				foreach($record as $k => $v) {
					$result .= "| " . Convert::raw2xml($k) . "";
				}
				$result .= " | 
 \n";
			}
			$result .= "";
			foreach($record as $k => $v) {
				$result .= "| " . Convert::raw2xml($v) . "";
			}
			$result .= " | 
 \n";
			
			$first = false;
		}
		$result .= "
\n";
		
		if($first) return "No records found";
		return $result;
	}
	
	/**
	 * Iterator function implementation. Rewind the iterator to the first item 
	 * and return it.
	 *
	 * Makes use of {@link seek()} and {@link numRecords()}, takes care of the 
	 * plumbing.
	 *
	 * @return array
	 */
	public function rewind() {
		if($this->queryHasBegun && $this->numRecords() > 0) {
			$this->queryHasBegun = false;
			return $this->seek(0);
		}
	}
	/**
	 * Iterator function implementation. Return the current item of the 
	 * iterator.
	 *
	 * @return array
	 */
	public function current() {
		if(!$this->currentRecord) {
			return $this->next();
		} else {
			return $this->currentRecord;
		}
	}
	/**
	 * Iterator function implementation. Return the first item of this iterator.
	 * @return array
	 */
	public function first() {
		$this->rewind();
		return $this->current();
	}
	/**
	 * Iterator function implementation. Return the row number of the current 
	 * item.
	 *
	 * @return int
	 */
	public function key() {
		return $this->rowNum;
	}
	/**
	 * Iterator function implementation. Return the next record in the iterator.
	 *
	 * Makes use of {@link nextRecord()}, takes care of the plumbing.
	 *
	 * @return array
	 */
	public function next() {
		$this->queryHasBegun = true;
		$this->currentRecord = $this->nextRecord();
		$this->rowNum++;
		return $this->currentRecord;
	}
	/**
	 * Iterator function implementation. Check if the iterator is pointing to a 
	 * valid item.
	 *
	 * @return boolean
	 */
	public function valid() {
		if(!$this->queryHasBegun) {
			$this->next();
		}
		return $this->currentRecord !== false;
	}
	/**
	 * Return the next record in the query result.
	 *
	 * @return array
	 */
	abstract public function nextRecord();
	/**
	 * Return the total number of items in the query result.
	 *
	 * @return int
	 */
	abstract public function numRecords();
	/**
	 * Go to a specific row number in the query result and return the record.
	 *
	 * @param int $rowNum Tow number to go to.
	 *
	 * @return array
	 */
	abstract public function seek($rowNum);
}