<?php defined('SYSPATH') or die('No direct script access.');
/**
 * Database expressions can be used to add unescaped SQL fragments to a
 * [Database_Query_Builder] object.
 *
 * For example, you can use an expression to generate a column alias:
 *
 *     // SELECT CONCAT(first_name, last_name) AS full_name
 *     $query = DB::select(array(DB::expr('CONCAT(first_name, last_name)'), 'full_name')));
 *
 * @package    Kohana/Database
 * @category   Base
 * @author     Kohana Team
 * @copyright  (c) 2009 Kohana Team
 * @license    http://kohanaphp.com/license
 */
class Kohana_Database_Expression {

	// Raw expression string
	protected $_value;

	/**
	 * Sets the expression string.
	 *
	 *     $expression = new Database_Expression('COUNT(users.id)');
	 *
	 * @return  void
	 */
	public function __construct($value)
	{
		// Set the expression string
		$this->_value = $value;
	}

	/**
	 * Get the expression value as a string.
	 *
	 *     $sql = $expression->value();
	 *
	 * @return  string
	 */
	public function value()
	{
		return (string) $this->_value;
	}

	/**
	 * Return the value of the expression as a string.
	 *
	 *     echo $expression;
	 *
	 * @return  string
	 * @uses    Database_Expression::value
	 */
	public function __toString()
	{
		return $this->value();
	}

} // End Database_Expression