oracle 使用触发器实现id自增

前提：存在数据库di_test,主键为id。
1.创建一个索引sequence

create sequence di_test_id 
minvalue 1  
nomaxvalue  
start with 1  
increment by 1  
nocache; 

2.创建一个触发器。在插入数据之前触发
create or replace trigger trigger_di_test_insert  
  before insert on di_test    
  for each row    
declare  
  -- local variable here  
begin    
  -- Column "ID" uses sequence di_test_id  
  select di_test_id.nextval into :new.ID from dual;  
end trigger_di_test_insert;