Hello,

Here is the test case:

CREATE DOMAIN TID AS INTEGER NOT NULL;
CREATE TABLE ENTITY (ENTITYID TID, ALLOTHERFIELDS TID,
CONSTRAINT PK_ENTITY PRIMARY KEY (ENTITYID));

SELECT RDB$NULL_FLAG FROM RDB$RELATION_FIELDS
WHERE RDB$RELATION_NAME = 'ENTITY' AND RDB$FIELD_NAME = 'ENTITYID'

Returns 'NULL' if executed on FB 1.5.3 server and
Returns '1' if executed on FB 2.0.1 server.

Why? Was that done intentionally?

It may seem like a not-so-important detail, however,
if you extract and compare metadata of the two, you will find
differences:

CREATE TABLE ENTITY (
<! ENTITYID TID NOT NULL,
!> ENTITYID TID,

which are not real differences at all, and that makes metadata
comparison more complicated than it could be.

Thanks,
Glebas