create table _test_blob (f_id serial, f_name varchar( 20 ), f_file byte);
create unique index ind on _test_blob(f_id);

procedure TForm1.Button1Click(Sender: TObject);
var
  Blob: TStream;
  FS: TFileStream;
begin
  if OpenDialog1.Execute then
    begin
      Table1.Append;
      Table1.FieldByName('f_name').Value := ExtractFileName(OpenDialog1.FileName);
      Blob := Table1.CreateBlobStream(Table1.FieldByName('f_file'), bmWrite);
      TRY
        Blob.Seek( 0 , soFromBeginning);
        FS := TFileStream.Create(OpenDialog1.FileName, fmOpenRead or fmShareDenyWrite);
        TRY
          Blob.CopyFrom(FS, FS.Size);
        FINALLY
          FS.Free;
        END;
      FINALLY
        Blob.Free;
      END;
    Table1.Post;  
    end;
end;