/fuel/core/classes/database/query/builder/join.php

<?php
/**
 * Database query builder for JOIN statements.
 *
 * @package    Fuel/Database
 * @category   Query
 * @author     Kohana Team
 * @copyright  (c) 2008-2009 Kohana Team
 * @license    http://kohanaphp.com/license
 */

namespace Fuel\Core;

class Database_Query_Builder_Join extends \Database_Query_Builder
{

	// Type of JOIN
	protected $_type;

	// JOIN ...
	protected $_table;

	// ON ...
	protected $_on = array();

	/**
	 * Creates a new JOIN statement for a table. Optionally, the type of JOIN
	 * can be specified as the second parameter.
	 *
	 * @param   mixed   column name or array($column, $alias) or object
	 * @param   string  type of JOIN: INNER, RIGHT, LEFT, etc
	 * @return  void
	 */
	public function __construct($table, $type = NULL)
	{
		// Set the table to JOIN on
		$this->_table = $table;

		if ($type !== NULL)
		{
			// Set the JOIN type
			$this->_type = (string) $type;
		}
	}

	/**
	 * Adds a new condition for joining.
	 *
	 * @param   mixed   column name or array($column, $alias) or object
	 * @param   string  logic operator
	 * @param   mixed   column name or array($column, $alias) or object
	 * @return  $this
	 */
	public function on($c1, $op, $c2)
	{
		$this->_on[] = array($c1, $op, $c2);

		return $this;
	}

	/**
	 * Compile the SQL partial for a JOIN statement and return it.
	 *
	 * @param   mixed  Database instance or instance name
	 * @return  string
	 */
	public function compile($db = null)
	{
		if ( ! $db instanceof \Database_Connection)
		{
			// Get the database instance
			$db = \Database_Connection::instance($db);
		}

		if ($this->_type)
		{
			$sql = strtoupper($this->_type).' JOIN';
		}
		else
		{
			$sql = 'JOIN';
		}

		// Quote the table name that is being joined
		$sql .= ' '.$db->quote_table($this->_table);

		$conditions = array();

		foreach ($this->_on as $condition)
		{
			// Split the condition
			list($c1, $op, $c2) = $condition;

			if ($op)
			{
				// Make the operator uppercase and spaced
				$op = ' '.strtoupper($op);
			}

			// Quote each of the identifiers used for the condition
			$conditions[] = $db->quote_identifier($c1).$op.' '.$db->quote_identifier($c2);
		}

		// if there are conditions, concat the conditions "... AND ..." and glue them on...
		empty($conditions) or $sql .= ' ON ('.implode(' AND ', $conditions).')';

		return $sql;
	}

	public function reset()
	{
		$this->_type =
		$this->_table = NULL;

		$this->_on = array();
	}

} // End Database_Query_Builder_Join