>I have been learning SQL 2008. After creating a few related tables, I added a few additional column to one of the tables. When I attempt to save the table structure I get an error telling me that the table can not be dropped and re-created.
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>1. Why when added a new column does SQL need to drop the original and re-create it?
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>2. If the constraint are the problem, why doesn't SQL drop the constraints and recreate them?

If you're using SSMS Design view it generates safer, but often more complex script than needed. You may be better if you use ALTER TABLE directly and not the design view.

Try saving the script right now (click on script button) and abandon this dialog. Then based on this script write correct query.