Subject Re: [firebird-support] alter column drop default (firebird 2.x)
Author Ann Harrison

> What is the difference between rdb$relation_fields.default_value and rdb
> $fields.default_value ?

The RDB$FIELDS table is equivalent to SQL Domains - meta definitions
for field types. When the system tables for Firebird were created,
SQL was not the only game in town. Under the rules of the day and
place, every column had to be based on a domain. When SQL DDL rules
were added to InterBase, that rule was kept, and when a column was
defined directly, without reference to a domain, InterBase and now
Firebird creates a dummy domain.

RDB$RELATION_FIELDS is the mapping between the domain and a column in
a table. The default value is one of the attributes of a domain that
can be changed when defining a column based on a domain.

Good luck,