Oracle 截取指定长度的字符

去掉回车，换行符号，截取指定长度的字符

具体代码示例：

--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(1000):='';
  v_Name varchar2(1000):='';
  v_Len int:=0;
  i int:=1;
  k int:=0;
begin
  --去掉回车，换行符号
  select trim(translate(P_Name,chr(13)||chr(10),',')) 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 1..v_Len 
  loop
    if (lengthb(substr(v_Name,-i,1))<>length(substr(v_Name,-i,1))) then
      k:=k+2;
    else
      k:=k+1;
    end if;
    if k<=P_Length then
      v_Temp:=v_Temp || substr(v_Name,-i,1);
    end if;
    if k>=P_Length then
      CONTINUE;
    end if;
  end loop;
    
  return(v_Temp);
  
end get_StringLen;

--Test
select get_StringLen('asdf',5) from dual;--返回结果：'asdf'
select get_StringLen('asd中国',5) from dual;--返回结果：'asd中'
select get_StringLen('asdfasdf',5) from dual;--返回结果：'asdfa'