How to select second grid and show data?

Helllo! I want to show data for second user on another form, but I am getting only first user data.
There is my code

sql.Text:= 'select * from korisnici where prezime = ' + StringGrid1.Cells[1, Index];

On English ( translated )

sql.text:= 'select * from users where lastname = ' + StringGrid1.Cells[1, Index];

How can I select another user? Please help, I searched but no results.

There is full code:

procedure TForm3.Button7Click(Sender: TObject);
var index: integer;
begin
with korisnici do
begin
  active:= false;
  sql.Clear;
  sql.Text:= 'select * from korisnici where prezime = ' + StringGrid1.Cells[1, Index];
  active:= true;
  form12.Caption:= fieldbyname('prezime').AsString + ' ' + fieldbyname('ime').AsString;
  form12.labelprezime.Caption:= fieldbyname('prezime').AsString + ' ' + fieldbyname('ime').AsString;
  form12.id.Text:= fieldbyname('id_odrzavanja').AsString;
  form12.licenca.text:= fieldbyname('licenca').AsString;
  form12.brlic.text:= fieldbyname('broj_licence').AsString;
  form12.brtel.Text:= fieldbyname('broj_telefona').AsString;
  form12.datkre.Text:= fieldbyname('datum_kreiranja').AsString;
  form12.datlic.Text:= fieldbyname('datum_licence').AsString;
  form12.redbr.Text:= fieldbyname('redni_broj').AsString;
  form12.region.Text:= fieldbyname('region').AsString;
  form12.email.Text:= fieldbyname('email').AsString;
  form12.Show;
end;
end;