Why  can't I commit updates to Detail table?

procedure TForm1.BitBtn1Click(Sender: TObject);
begin
   IBDatabase1.ApplyUpdates([IBQuery1,IBQuery2]);
end;

I used a TIBUpdateSQL for each TIBQuery and Set  TIBQuery 's CachedUpdates
to True;
But when I Insert  a record , and then Post them, But Detail Query doesn't
been saved .
Why?

Thanks a lot !

Ken