SQL decode question

Hi all,

I have a question regarding the decode function in SQL. I am trying to use it in the following way
select
  decode(Document.type, 'Long Text', Long_Document.long_text, 'Short Text', Short_Document.short_text, '')
 ...
from... where...;

The problem is that Long_Document.long_text is of type LONG, while Short_Document.short_text is of type VARCHAR2(2000). I know decode is expecting the parameters to have the same data type, so I was trying to use some conversion functions (like to_char). But I was still given "inconsistent datatype" error.

Any ideas?

Thanks in advance!

Anton