What happens if you insert the empty string into the same type of field from sqlplus (Update: actually, I would expect the same results as demerphq's suggesstion above, but you never know)? If you get the same result, then its not DBI/DBD (maybe the empty string is interpreted as null in a char column?). If you get different results, then you could post a DBI trace to the DBI mailing list and ask for help there.