program unique_expr (input,output);
    DATABASE PERS = FILENAME 'PERSONNEL';

    begin
    READY PERS;
    START_TRANSACTION READ_ONLY;

    FOR E IN EMPLOYEES
       WITH UNIQUE D IN DEGREES WITH D.EMPLOYEE_ID = E.EMPLOYEE_ID
          writeln (E.FIRST_NAME, ' ', E.LAST_NAME,
                  ' has one and only one college degree.');
    END_FOR;

    COMMIT;
    FINISH;
    end.