No. The query I posted would only select the data as it exists from the table, convert it to the appropriate types and return you the result.
If you want to change the data types, use the alter table command.
-- these are only examples. Look up alter table on MSDN and
-- make appropriate changes to fit your needs. Also, first
-- test on a development server.
ALTER TABLE TheTable ALTER COLUMN transdate DATE NOT NULL;
ALTER TABLE TheTable ALTER COLUMN qty FLOAT NOT NULL;