求自增函数

Question

求单据编号函数 格式如AMDYYMMDDXXXX  
 
例：今天是20110218  执行函数单据号递增格式如：AMD201102180001,AMD201102180002,AMD201102180003

Answer 1

怎么写啊 我要生成像这种单据号AMD201102180001 

Answer 2

create sequence t_seq;
select 'AMD'||to_char(sysdate,'yyyymmdd')||lpad(t_seq.nextval,4,'0') from dual;

Answer 3

scott@YPCOST> create sequence billno_seq increment by 1 start with 1;Sequence created.scott@YPCOST> create or replace function F_billno
  2  return varchar2
  3  as
  4  billno varchar2(30);
  5  begin
  6  select 'AMD'||to_char(sysdate,'yyyymmdd')||lpad(billno_seq.nextval,4,0)
  7  into billno from dual;
  8  return billno;
  9  end;
 10  /Function created.scott@YPCOST> select f_billno from dual;F_BILLNO
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AMD201102180001