dbimport error 525

While importing database via dbimport error 525 Failure to satisfy referential constraint... occurs. The problem is that the error appears while trying to run: alter table aaa add constraint ( foreign key ...) on columns with containing null values ( declared as not null and varchar(3,0)) I have check unload_file via hd ( hexadecimal dump ) and od -h ( hexa.dump) and the unload file is good There are real null values.I have tried several sequences how to repair it 1. drop table , create foreign key and load data 2. drop table , load data and add foreign key 1. was succesfull It is possible to do it this way but it makes me confused because where i run dbimport next time the same errors appear again and on the same tables or sometimes on different tables ( that were good in the first dbimport) I found out that it appears only on columns declared as varchar(). I have changed all columns that are primary keys and of course referenced foreign key to simple char and there were no problems Is it good to use varchar for columns used as primary key ?? According to that experience i would not recommend . Or it it some bug ??? We are running in V 5.01 U. thank you for any experience with varchar as primary key -- Katarina Hamzova Voice : +42 7 3783200 SWH s.r.o Bratislava Fax : +42 7 377433 Slovakia Internet : Katarina.Hamzova@swh.sk