oracle varchar2序列的使用

create table book( bookId varchar2(4) primary key, name varchar2(20) ); --创建序列 create sequence book_seq start with 1 increment by 1 NOMAXvalue 
NOCYCLE 
NOCACHE; --创建触发器 create or replace trigger book_trigger
before insert on book for each row begin select book_seq.nextval into :new.bookId from dual; end ; --添加数据 insert into book(name) values ('cc'); insert into book(name) values ('dd'); commit; select * from book; 

注意 :new.bookId要为book表中的id的名称 . :new称之为伪记录变量, 记录着将要插入的变量值. 结果如图