exclude column from select *

 In oracle how do you exclude one or  two columns from select * from a range of tables. These table has a common column like source_date in different position?

The reason behind this is that I need to diff table data for two databases there's more than one hundread tables and  I plan to export the data to text file and use OS diff command. Is there a good freeware that can do automated data comparesion?

Thanks in advance any advices.

Joe