>Bases on your and Sergey's input I will have to go through all my SQL server tables and make sure I have an empty string as default on those columns that may affect my program. Not a trivial task since the app has about 90+ tables.

If this is what you want, then, yes, in that context, it would require a few minutes, at least. :)

I have an application with 425 lists, 275 tables, 5000 fields, 3000 indexes and so on. When comes time to do some normalization like that, yes, it's an overnight task with a lot of test sequence.