求更新的SQL 语句
查找出“目标”这列，取出就是在com之前的那个点，到com之前之前的那个点之间
注意com.cn                  
 URL                          目标
http://news.17173.com/      17173
http://mail.airland.com/     airland
http://wenku.baidu.com/      baidu
http://www.surveyhead.com/  surveyhead
http://photo.weibo.com/      weibo
http://webmail.mail.163.com/ 163
http://photo.renren.com/     renren
https://my.alipay.com/       alipay
http://s96.917st.com/        917st
http://bbs.egou.com/         egou
http://9yinbbs.woniu.com/   woniu
http://mail.qq.com/     qq
http://quan.51fanli.com/    51fanli
http://quote.eastmoney.com/  easymoney

------解决方案--------------------

if object_id('[TB]') is not null drop table [TB]

go

create table [TB] (URL nvarchar(56),目标 nvarchar(20))

insert into [TB]

select 'http://news.17173.com/','17173' union all

select 'http://mail.airland.com/','airland' union all

select 'http://wenku.baidu.com/','baidu' union all

select 'http://www.surveyhead.com/','surveyhead' union all

select 'http://photo.weibo.com/','weibo' union all

select 'http://webmail.mail.163.com/','163' union all

select 'http://photo.renren.com/','renren' union all

select 'https://my.alipay.com/','alipay' union all

select 'http://s96.917st.com/','917st' union all

select 'http://bbs.egou.com/','egou' union all

select 'http://9yinbbs.woniu.com/','woniu' union all

select 'http://mail.qq.com/','qq' union all

select 'http://quan.51fanli.com/','51fanli' union all

select 'http://quote.eastmoney.com/','easymoney'



select * from [TB]





SELECT url,REVERSE(SUBSTRING(REVERSE(REPLACE(url,'.com/','')),0,PATINDEX('%.%',REVERSE(REPLACE(url,'.com/','')))))

FROM TB



/*

url	(无列名)

http://news.17173.com/	17173

http://mail.airland.com/	airland

http://wenku.baidu.com/	baidu

http://www.surveyhead.com/	surveyhead

http://photo.weibo.com/	weibo

http://webmail.mail.163.com/	163

http://photo.renren.com/	renren

https://my.alipay.com/	alipay

http://s96.917st.com/	917st

http://bbs.egou.com/	egou

http://9yinbbs.woniu.com/	woniu

http://mail.qq.com/	qq

http://quan.51fanli.com/	51fanli

http://quote.eastmoney.com/	eastmoney*/

------解决方案--------------------
借用l楼的表。

select url,目标=parsename(url,2) from tb