如何在zend框架中使用子查询执行查询

你好，我需要用 Zend_Db_Select 编写这个 sql，但我不知道如何编写子查询。我将不胜感激任何帮助。谢谢。

SELECT * FROM advert WHERE categoryId
           IN (
             SELECT id
              FROM `tree`
              WHERE `lft` BETWEEN 
               (SELECT lft FROM tree WHERE id = '2') AND 
               (SELECT rgt FROM tree WHERE id = '2'))

// create the main query
$select = new Zend_Db_Select();

//create the subquery
$subSelect = new Zend_Db_Select();

// using the subquery in main query
$select->where('table.field IN(?)', $subSelect->assemble());