[NumLock]

Код:

procedure TForm1.ButtonLoginClick(Sender: TObject);
begin
  ADOQuery1.SQL.Text:='select Password from Users where UserName=:UserName';
  ADOQuery1.Parameters.ParamByName('UserName').Value:=EditUserName.Text;
  ADOQuery1.Open;
  if EditPassword.Text=ADOQuery1.FieldByName('Password').AsString then
  begin
    { do it }
  end;
end;