先上问题： 我这里有十个表，我要在这十个表中查询字段tid = 40的结果 方法： 
SELECT * FROM `yle_forum_attachment_0` WHERE `tid` = '50' 
union all 
SELECT * FROM `yle_forum_attachment_1` WHERE `tid` = '50' 
union all 
SELECT * FROM `yle_forum_attachment_2` WHERE `tid` = '50'
union all 
SELECT * FROM `yle_forum_attachment_3` WHERE `tid` = '50' 
union all 
SELECT * FROM `yle_forum_attachment_4` WHERE `tid` = '50' 
union all 
SELECT * FROM `yle_forum_attachment_5` WHERE `tid` = '50' 
union all 
SELECT * FROM `yle_forum_attachment_6` WHERE `tid` = '50' 
union all 
SELECT * FROM `yle_forum_attachment_7` WHERE `tid` = '50' 
union all 
SELECT * FROM `yle_forum_attachment_8` WHERE `tid` = '50' 
union all 
SELECT * FROM `yle_forum_attachment_9` WHERE `tid` = '50'
 注意：所有表的结构必须一致才可以使用本方法！