oracle取项目编号

select to_char(sysdate,'yyyyMMddHH24miss')||decode(length(datenumber.nextval) ,1 ,'0000'||datenumber.nextval ,2,'000'||datenumber.nextval,3,'00'||datenumber.nextval,4,'0'||datenumber.nextval,5,datenumber.nextval) from dual;