Credit system to make application in database (MyDAC)

Question

I want to make a credit system. If have user credits "warning: you have credit! quantity: [Jeton value in column]", If have not user credits "warning: you have not credit!" I used MyDAC Components

Jeton: User credit column.(In database)

How do I make it?

I tried to make

MyQuery1.Close;
 MyQuery1.SQL.Text :=' select* from uyeler '+
                     'where nick=:0 and jeton=:1';

 MyQuery1.Params[0].AsString:=Edit1.Text;
 MyQuery1.Params[1].AsString:=?must?;

 MyQuery1.open;

 If MyQuery1.RecordCount=0 Then
  Begin

  MessageDlg('warning: you have not credit!', mtWarning,[mbOK],0)

 End
 Else
 Begin

  MessageDlg('warning: you have credit! quantity: (Jeton value in column)', mtWarning,[mbOK],0)

End;

Answer 1

If the jeton field is the credit, you can write something like this.

 MyQuery1.Close;
 MyQuery1.SQL.Text :='select jeton from uyeler where nick=:0';
 MyQuery1.Params[0].AsString:=Edit1.Text;
 MyQuery1.open;

 If (MyQuery1.IsEmpty) or (MyQuery1.FieldByName('jeton').AsDouble<=0) Then
  Begin
   MessageDlg('warning: you have not credit!', mtWarning,[mbOK],0)
  End
  Else
  Begin
   MessageDlg(Format('warning: you have credit! quantity: (%n)',[MyQuery1.FieldByName('jeton').AsDouble]), mtWarning,[mbOK],0);
  end;