How about using a stored procedure with a cursor and a handler?
example:
PROCEDURE movePW()
BEGIN
declare thisID, thisPass varchar(64);
declare keepGoing tinyint;
declare original cursor for select id, user_pass from user1;
declare continue handler for not found set keepGoing = 0;
set keepGoing = 1;
open original;
fetch original into thisID, thisPass;
while keepGoing = 1 do
update wp_users set user_pass=thisPass where id=thisID;
fetch original into thisID, thisPass;
end if;
fetch items into thisID;
end while;
END