var 
    bf:TBlobField;
    s:TMemoryStream;
begin
     bf:=TBlobField(qc.fieldbyname('creater_logo'));
     s:=TMemoryStream.create();
     bf.SaveToStream(s);
     s.SaveToFile('blabla.bla');
     s.free;
end

var fs:TFileStream;
begin
     if not od.execute then exit;
     fs:=TFileStream.create(od.filename, 0 );
     with q do
     begin
          close;
          sql.clear;
          sql.add('update product set product_photo=:p0 where product_id=:p1');
          params[ 0 ].loadfromstream(fs,ftBlob);
          params[ 1 ].asinteger:=qp.fieldbyname('product_id').asinteger;
          execsql;
     end;
     qp.close;
     qp.open;
     fs.free;
end;