Porting to Oracle - problem with empty strings/nulls

Hello guys,

I need and advice on how to turn NULLs into empty strings back.

We have a legacy system (standalone desktop application) written in Smalltalk that uses MS Access via ODBC as the back-end. Our management decided to port the application to Oracle 9.2 (partly due to marketing reasons, partly for further enhancement).

I have created a DB on Oracle and converted all the data from the Access DB. Unfortunately, it is well-known that Oracle treats empty strings as NULLs, and our legacy applications is somewhat poorly designed - it doesn't have a separate persistent layer but a lots of SQLs spreaded all over the code instead. What is the worst, there are many places in the code where a string fetched from the DB is checked if it is empty, so the application became totally out of order. There is absolutely impossible for us to change all these SQLs and equality checks in the code, so we need a solution 'in general'.

Could you please suggest any solution (if such exists :-) how to get empty strings instead of NULLs as results of SQLs in Oracle? May be you know of an Oracle ODBC driver providing such a feature? Could I achieve the goal, for example, by using triggers or views ore any other Oracle features?

Thanks in advance.

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Best regards,
Deloni, SPb, Russia