--Function

 --去掉前后空格，截取字符，字符长度为P_Length

 create or replace function get_StringLen

 (

   P_Name IN VARCHAR2,

   P_Length IN int

 ) return varchar2 is

   v_Temp varchar2():='';

   v_Name varchar2():='';

   v_Len int:=;

   i int:=;

   k int:=;

 begin

   --去掉回车，换行符号

   select trim(translate(P_Name,chr()||chr(),',')) into v_Name from dual; 

   --取字串的长度

   select length(v_Name) into v_Len from dual; 

   --循环来取

   for i in reverse ..v_Len

   loop

     if (lengthb(substr(v_Name,-i,))<>length(substr(v_Name,-i,))) then

       k:=k+;

     else

       k:=k+;

     end if;

     if k<=P_Length then

       v_Temp:=v_Temp || substr(v_Name,-i,);

     end if;

     if k>=P_Length then

       CONTINUE;

     end if;

   end loop;

   return(v_Temp);

 end get_StringLen;

 --Test

 select get_StringLen('asdf',) from dual;--返回结果：'asdf'

 select get_StringLen('asd中国',) from dual;--返回结果：'asd中'

 select get_StringLen('asdfasdf',) from dual;--返回结果：'asdfa'