Oracle 如何定义自动增量autocreament的主键ID?

MySQL的ID非常方便定义，只要指定其字段的自动增量属性即可。
但是Oracle不行，需要定义sequence和triggedr，当然trigger可以不定义，但是不方便。
表定义如下：
CREATE TABLE GAME
(
  ID           
INTEGER                         NOT NULL,
  GAME_DATE    
DATE                            NOT NULL,
  START_TIME    DATE,

  END_TIME      DATE,
  GAME_RULE_ID  INTEGER
)
我想插入时不必指出Id
INSERT INTO game(game_date, start_time, Game_rule_id)
VALUES (to_date(‘2003/05/03′, ‘yyyy/mm/dd’), to_date(‘21:02:44′,
‘hh24:mi:ss’), 1) ；
首先定义sequence
create sequence game_sequence
start with 1
increment
by 1;
然后定义trigger
create TRIGGER game_trigger
BEFORE INSERT
ON game
REFERENCING
NEW AS NEW
FOR EACH ROW
BEGIN
SELECT
game_sequence.nextval INTO :NEW.ID from dual;
END;
查看已经存在的sequence和trigger
SELECT sequence_name from user_sequences;
SELECT trigger_name from user_triggers;
删除已经定义的sequence和trigger
DROP sequence game_sequence;
DROP trigger game_trigger;
禁用和启用trigger
ALTER trigger game_trigger disable;
ALTER trigger game_trigger enable;