Oracle 阻止表中的check_date列的将来日期

SQL> create table t (
  2    dt date
  3  );
SQL>
SQL> alter table t add constraint ck check (dt < sysdate);
alter table t add constraint ck check (dt < sysdate)
                                            *
ERROR at line 1:
ORA-02436: date or system variable wrongly specified in CHECK constraint


SQL>
SQL> create or replace trigger tt
  2  before insert or update on t
  3  for each row
  4  begin
  5    if :new.dt > sysdate then
  6      raise_application_error(-20001, 'Date in the future!');
  7    end if;
  8  end;
  9  /
SQL> show err
No errors.
SQL>
SQL> insert into t values (sysdate+1);
insert into t values (sysdate+1)
            *
ERROR at line 1:
ORA-20001: Date in the future!
ORA-06512: at "CHRIS.TT", line 3
ORA-04088: error during execution of trigger 'CHRIS.TT'