SQL查询问题(从一个表到另一个表随机添加值)

update A 
set proxy= (select top 1 proxy from Proxies P WHERE P.proxy-P.proxy=A.proxy-A.proxy order by newid()) 
FROM Accounts A 

http://sqlfiddle.com/#!18/c68ce/4/1

where

update Accounts set proxy= (select top 1 proxy from Proxies order by newid())
where Accounts.col =something

UPDATE t1
SET t1.proxy= t2.proxy
FROM Accounts t1
CROSS APPLY (
   SELECT TOP 1 p.proxy
   FROM Proxies p
   WHERE p.proxy= t1.proxy
   ORDER BY newid()
) t2