CREATE SEQUENCE sequence  //创建序列名称   [INCREMENT BY n]  //递增的序列值是n 如果n是正数就递增,如果   是负数就递减 默认是1   [START WITH n]    //开始的值,递增默认是minvalue 递减是  // maxvalue   [{MAXVALUE n | NOMAXVALUE}] //最大值   [{MINVALUE n | NOMINVALUE}] //最小值   [{CYCLE | NOCYCLE}] //循环/不循环   [{CACHE n | NOCACHE}];//分配并存入到内存中

NEXTVAL 返回序列中下一个有效的值，任何用户都可以引用

CURRVAL 中存放序列的当前值

NEXTVAL 应在 CURRVAL 之前指定 ，二者应同时有效

select emp_id_seq.nextval from dual;

select emp_id_seq.currval from dual;

使用DROP SEQUENCE 语句删除序列 

修改序列 

Alter sequence seqEmp maxvalue 5;

Select seqEmp.nextval from dual;

create table cdpt(

id number(6),

name varchar2(30),

constraint pk_id primary key(id)

);

Create sequence seq_cdpt

Increment by 1

Start with 1

Maxvalue 999999

Minvalue 1

Nocycle

nocache

insert into cdpt values(seq_cdpt.nextval,’feffefe’);

commit;

select * from cdpt;