Oracle自动增长的序列号

首先建立序列：

Create sequence user_id  
Increment by 1  
Start with 1  
Maxvalue 1.0E28  
Minvalue 1 nocycle  
Cache 20  
Noorder;

然后建立触发器

create or replace trigger AUTO_ID_ADD
before insert on userinfo
referencing old as old_value
new as new_value
for each row
begin
select USER_ID.nextval into :new_value.id from dual;
end;

这样就完成了ID自动增长。