Q:如何在執行時期建立計算欄位?
A: 參考下列程式碼:
  with FieldDefs do   
  begin      
    // Create a calculated TField, assign properties,
    //  and add to MyTable's field definitions array. 
    TaxAmount := TFloatField.Create(MyTable);      
    with TaxAmount do
    begin       
      FieldName := 'TaxAmount';       
      Calculated := True;
      Currency := True;        DataSet := MyTable;
      Name := MyTable.Name + FieldName;
      MyTable.FieldDefs.Add(Name, ftFloat, 0, false);     
    end;    
  end;