Hello,

While browsing through system tables, I found out that the field
RDB$NULL_FLAG is found both in RDB$TYPES and RDB$RELATION_FIELDS. I
understand that rdb$types contain domain data and rdb$relation_fields
contain column data. What I don't understand is why is null_flag needed
in rdb$relation_fields (every column has a domain, and it information
can be pulled from there)?

I'd also like to know what are the implications if the value of
null_flag is different in rdb$types and rdb$relation_fields?

Third, I'd like to know what is the proper way of changing a column from
not null to null? Do I just change null_flag in rdb$relation_fields?

I'm not sure if this is the right place to ask, so I'll ask at devel
list if I don't get any answers here.

TIA

--
Milan Babuskov
http://fbexport.sourceforge.net
http://www.flamerobin.org