Can you use JOIN in UPDATE ?

YES.

e.g.
update
set
from

where

Remember the syntax :
UPDATE TableA
SET colname=TableB.colname ( or anything else)
FROM TableA, TableB

WHERE  <join condition>

Have a look at following links for more information :

http://www.tek-tips.com/faqs.cfm?fid=1958

http://www.bennadel.com/blog/938-Using-A-SQL-JOIN-In-A-SQL-UPDATE-Statement-Thanks-John-Eric-.htm

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