怎么更新oracle数据库中blob对象的十六进制数值

create or replace procedure pro_union_binary(recordid number) is  cursor v_cursor is    select * from tb_image_info where itemid = recordid order by ilineid;  v_item       v_cursor%rowtype;  v_count      integer default 0;  v_ilineid    integer default 0;  v_sql        varchar2(32767) default '';  v_characters clob;  v_seq        integer default 1;  v_blob       blob;  warning      integer;  dest_offset1 integer := 1;  src_offset1  integer := 1;  lang_ctx     INTEGER := DBMS_LOB.default_lang_ctx;begin  select count(*) into v_count from tb_image_info where itemid = recordid;  if v_count = 1 then    return;  end if;  open v_cursor;  loop    fetch v_cursor      into v_item;    exit when v_cursor%notfound;    if v_ilineid = 0 then      v_ilineid := v_item.ilineid;    end if;    v_characters := v_characters || v_item.image; --获取已经得到的二进制文件流对应的十六进制字符串   if v_seq = v_count then      if dbms_lob.getlength(v_characters) = 0 then        return;      end if;      DBMS_LOB.createtemporary(v_blob, TRUE);      DBMS_LOB.OPEN(v_blob, DBMS_LOB.lob_readwrite);      DBMS_LOB.convertToBlob(v_blob,                             v_characters,                             DBMS_LOB.lobmaxsize,                             dest_offset1,                             src_offset1,                             DBMS_LOB.default_csid,                             lang_ctx,                             warning);          v_sql := 'update tb_image_info set image0 = :1 where ilineid = :2';      execute immediate v_sql        using v_blob, v_ilineid;    end if;    v_seq := v_seq + 1;  end loop;end pro_union_binary;