我有一个有点复杂的查询:
(SELECT category_id AS id, content_title AS title, content AS detail, 'content' AS type
FROM category_content
WHERE $where
ORDER BY id DESC)
UNION
(SELECT news_id AS id, news_title AS title, news_detail AS detail, 'news' AS type
FROM news
WHERE $where
ORDER BY id DESC)
如何将此查询更改为Zend_Db_Select
对象?