The following information is quoted from Oracle's documentation:

Oracle currently treats a character value with a length of zero as null. However, this may not continue to be true in future releases, and Oracle recommends that you do not treat empty strings the same as nulls.

This is not a correct implementaion, but it is what Oracle currently does. A NULL value is an unknown value... an empty string is not unknown -- it is known to be empty.

So, the problem here is the empty strings you want to insert are being converted to NULLs which violate the NOT NULL constraint on the columns. While this may not be much of a "fix", your options would seem to be:

• Remove the NOT NULL column constraints
• Insert some other value into the columns (like a single space.)

I hope this helps... (or at least explains what is happening.)