PrestaShop search query

[Glenskie]

hi im new at prestashop and i need to know a couple things so i can change a query for the search... i need to know how to have the php search for a product id and the product from two different tables ... is this the code that uses the word from the search box to look in the database tables or is this the wrong query ? im just trying to find the query  

public static function find($id_lang, $expr, $page_number = 1, $page_size = 1, $order_by = 'position',
		$order_way = 'desc', $ajax = false, $use_cookie = true, Context $context = null)
	{
		if (!$context)
			$context = Context::getContext();
		$db = Db::getInstance(_PS_USE_SQL_SLAVE_);

		// Only use cookie if id_customer is not present
		if ($use_cookie)
			$id_customer = $context->customer->id;
		else
			$id_customer = 0;

		// TODO : smart page management
		if ($page_number < 1) $page_number = 1;
		if ($page_size < 1) $page_size = 1;

		if (!Validate::isOrderBy($order_by) || !Validate::isOrderWay($order_way))
			return false;

		$intersect_array = array();
		$score_array = array();
		$words = explode(' ', Search::sanitize($expr, $id_lang));

		foreach ($words as $key => $word)
			if (!empty($word) && strlen($word) >= (int)Configuration::get('PS_SEARCH_MINWORDLEN'))
			{
				$word = str_replace('%', '\\%', $word);
				$word = str_replace('_', '\\_', $word);
				$intersect_array[] = 'SELECT si.id_product
					FROM '._DB_PREFIX_.'search_word sw
					LEFT JOIN '._DB_PREFIX_.'search_index si ON sw.id_word = si.id_word
					WHERE sw.id_lang = '.(int)$id_lang.'
						AND sw.id_shop = '.$context->shop->id.'
						AND sw.word LIKE
					'.($word[0] == '-'
						? ' \''.pSQL(Tools::substr($word, 1, PS_SEARCH_MAX_WORD_LENGTH)).'%\''
						: '\''.pSQL(Tools::substr($word, 0, PS_SEARCH_MAX_WORD_LENGTH)).'%\''
					);

				if ($word[0] != '-')
					$score_array[] = 'sw.word LIKE \''.pSQL(Tools::substr($word, 0, PS_SEARCH_MAX_WORD_LENGTH)).'%\'';
			}
			else
				unset($words[$key]);

		if (!count($words))
			return ($ajax ? array() : array('total' => 0, 'result' => array()));

		$score = '';
		if (count($score_array))
			$score = ',(
				SELECT SUM(weight)
				FROM '._DB_PREFIX_.'search_word sw
				LEFT JOIN '._DB_PREFIX_.'search_index si ON sw.id_word = si.id_word
				WHERE sw.id_lang = '.(int)$id_lang.'
					AND sw.id_shop = '.$context->shop->id.'
					AND si.id_product = p.id_product
					AND ('.implode(' OR ', $score_array).')
			) position';

		$sql = 'SELECT cp.`id_product`
				FROM `'._DB_PREFIX_.'category_group` cg
				INNER JOIN `'._DB_PREFIX_.'category_product` cp ON cp.`id_category` = cg.`id_category`
				INNER JOIN `'._DB_PREFIX_.'category` c ON cp.`id_category` = c.`id_category`
				INNER JOIN `'._DB_PREFIX_.'product` p ON cp.`id_product` = p.`id_product`
				'.Shop::addSqlAssociation('product', 'p', false).'
				WHERE c.`active` = 1
					AND product_shop.`active` = 1
					AND product_shop.`visibility` IN ("both", "search")
					AND product_shop.indexed = 1
					AND cg.`id_group` '.(!$id_customer ?  '= 1' : 'IN (
						SELECT id_group FROM '._DB_PREFIX_.'customer_group
						WHERE id_customer = '.(int)$id_customer.'
					)');
		$results = $db->executeS($sql);