oracle 生成流水号

create sequence TRADE_NO_SEQ
minvalue 1
maxvalue 999999
start with 3618
increment by 1
cache 20
cycle;




 create or replace function GET_TRADE_NO_FUN  return varchar2 is


  TRADE_NO varchar2(50);
  seq_num VARCHAR2(10);
begin
    select TRADE_NO_SEQ.Nextval into seq_num from DUAL;
     if seq_num<=999999 THEN
         TRADE_NO:=Trim(TO_CHAR(seq_num,'000000'));
     end if;
    select TO_CHAR(SYSDATE,'YYMMDD')||TRADE_NO into TRADE_NO from DUAL;
 return TRADE_NO;
end;