you need to either built your table with all it's columns, or use the EXEC(@sqlstatement) to do the alter an iupdate.
the database engine expects either a GO statement, so it knows the ALTER command is completed, so that it is commited to the metatadata.
the best solution build the whole thing in one pass:
select Table1.*,'Yes' As [Edit]
into Table2
from Table1
where date > '07/01/2009'
Lowell