4个表
news_info , news_class , city_info , user_info
news_info 字段：id,news_tit，news_content，addDate，tj，city_id
news_class 字段：id,news_class，news_class_fid，news_class_px，user_id
city_info 字段：id,city，fid
user_info 字段：id,username,userEmail
select a.news_tit,a.news_content ,b.news_class,c.city,d.username,d.useremail
from news_info a,news_class b,city_info c,user_info d
where a.city_id=c.id and b.user_id=d.id and a.id=b.news_class_fid
