create or replace Function BlobToVarchar (Blob_In In Blob) Return clob
 Is
     V_Varchar );
      V_Varchar1 );
     V_Start Pls_Integer :;
     V_Buffer Pls_Integer :;
 Begin

     If Dbms_Lob.Getlength(Blob_In) Is Null Then
         Return '';
     End If;
     V_Varchar1 := '';
  --return to_char(Ceil(Dbms_Lob.Getlength(Blob_In) / V_Buffer));
     ..Ceil(Dbms_Lob.Getlength(Blob_In) / V_Buffer) Loop
         --当转换出来的字符串乱码时，可尝试用注释掉的函数
         --V_Varchar := Utl_Raw.Cast_To_Varchar2(Utl_Raw.Convert(Dbms_Lob.Substr(Blob_In, V_Buffer, V_Start),'SIMPLIFIED CHINESE_CHINA.ZHS16GBK', 'AMERICAN_THE NETHERLANDS.UTF8'));
         V_Varchar :=  Utl_Raw.Cast_To_Varchar2(Dbms_Lob.Substr(Blob_In, V_Buffer, V_Start));
         V_Varchar1 := V_Varchar1 || V_Varchar;

         V_Start := V_Start + V_Buffer;
     End Loop;

     Return V_Varchar1;

 End Blob_To_Varchar;

update DR_RPT_REPORT_DATASOURCE
set data_sql =
c2b(to_clob((select replace(Blob_To_Varchar(data_sql),'XXX','XXX') from DR_RPT_REPORT_DATASOURCE where data_id
='XXXX' ))) where data_id = '' ;