Changing NOT NULL for an Existing Column

Changing NOT NULL for an Existing Column

Changing NOT NULL for an Existing Column : Multi-thousand tips to make your life easier.

To change the NOT NULL constraint on an existing column, use the following SQL. To allow null, use NULL; to disallow null, use 1.

update
  RDB$RELATION_FIELDS
set
  RDB$NULL_FLAG = *** HERE ***
where
  (RDB$FIELD_NAME = 'COLUMNNAME')
  and (RDB$RELATION_NAME = 'TABLENAME');