ORACLE中创建自增的ID字段

1、创建序列
 create *sequence_name*  increment by 1 start with 1 maxvalue 999999999;
2、创建触发器---(创建一个基于该表的before insert 触发器，在触发器中使用该SEQUENCE)
create or replace trigger *triger_name*
before insert on       *table_name*
referencing old as old new as new for each row
begin
select  *sequence_name.nextval into :new.id from dual;
end;