Commented by: @asfernandes

How did you change the field type?

Commented by: Jonas Jasas (jon)

Using IBExpert. I doubleclicked on the field name in the table fields list and then selected domain from drop-down list.

update RDB$RELATION_FIELDS set
RDB$FIELD_SOURCE = 'TREGNR',
RDB$COLLATION_ID = -1
where (RDB$FIELD_NAME = 'TEST') and
(RDB$RELATION_NAME = 'SUTARCIUANTR')

Changed from: CREATE DOMAIN TKODAS AS VARCHAR(20) CHARACTER SET ISO8859_13 COLLATE LT_LT;
Changed to: CREATE DOMAIN TREGNR AS INTEGER;

Commented by: @dyemanov

Then forward your issue to the IBExpert developers. Direct manipulations with system tables should be done with a lot of care, it's undocumented and potentially dangerous feature. The officially supported ALTER statement doesn't allow conversions from strings to integers, as it's guaranteed to provide you with problems like the described one.

Commented by: Sean Leyne (seanleyne)

As Dmitry has pointed out, direct manipulations of system tables is not officially supported by the project.