text: -- set default value for new field
  UPDATE PERSON_EXT_T
  SET CITIZENSHIP_TYPE_CODE = (SELECT CITIZENSHIP_TYPE_CODE FROM CITIZENSHIP_TYPE_T WHERE DESCRIPTION = 'US CITIZEN OR NONCITIZEN NATIONAL');
  
  -- make new field a non-null field
  ALTER TABLE "PERSON_EXT_T" MODIFY ( "CITIZENSHIP_TYPE_CODE" NUMBER(15,5) NOT NULL );