Oracle自动增长

如何在Oracle中实现类似自动增加ID的功能?
使用触发器。使用触发器
1.1 创建序列
create sequence SEQ
minvalue 1
maxvalue 999999999999999999999999999
start with 1
increment by 1
cache 30
order;
1.2 创建表
CREATE TABLE table1
(
id NUMBER PRIMARY KEY,
username VARCHAR2(50)
);

1.3 创建触发器
CREATE OR REPLACE TRIGGER table1_tg
BEFORE INSERT ON table1 FOR EACH ROW
BEGIN
SELECT table1_seq.NEXTVAL INTO :NEW.id FROM DUAL;
END;