Swap column values in sql server 2008

Suppose we have a table named USER with 3 columns: USERID, USERName, USERAddress.

              USERID: int 

              USERName: varchar(100) 

              USERAddress: varchar(100) 

Swap with the temporary variable:
-----------------------------------------------

DECLARE @temp AS varchar(10)
 
UPDATE USER SET @temp=USERAddress, USERAddress=USERName, USERName=@temp
 

Hope freshers will find it helpful :)