What SQL Server datatype are you having problem with?

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>I'm using piece of code below(from Doug Henning's article) for transfering data between a database in dbf to another in a sql server.This works fine, but there is a problem that I could not solve without changing the structure of the destination table.When the data in the dbf is empty and the field destination does not acept nulls, I get an error saying that no data was transfered and the field does not accept nulls.But there was data being transfered, the data was just empty, not null.
>In a XML schema is the blank field interpreted as NULL?This can be changed?
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