1、创建数据库

create table USERINFO
(
USERNO NUMBER not null,
USERNAME NVARCHAR2(20),
USERPWD NVARCHAR2(20)
)

2、创建触发器

create sequence SEQ_Userinf start with 1 increment by 1
nomaxvalue
nominvalue
nocache;

CREATE OR REPLACE TRIGGER tg_test
BEFORE INSERT ON Userinfo
FOR EACH ROW WHEN (new.userNo is null)
begin
select SEQ_Userinf.nextval into:new.userNO from dual;
end;

3、测试，插入数据

insert into USERINFO(USERNAME,USERPWD) values('范围广','322');

 

https://www.cnblogs.com/nucdy/p/5615214.html