Paradox BCD 字段 - 数字超出范围错误

Question

I'm attempting to update an old Paradox (BDE) table using an older Delphi XE6 application. One particular table has two fields; a Date field, and a BCD field. I'm unable to post a new record to the (FuelSurch) table due to the BCD (FuelSur) field which is throwing a "Number is out of range" error.

So I wrote a quick test, but still the same issue. Here are the FuelSurch table field specifications.

I just added a button to a form and this procedure fires when clicked.

procedure TTestForm.BCDTestBtnClick(Sender: TObject);
var
  Bcd: TBcd;
begin
  POE_Data.FuelSurch.Open;
  POE_Data.FuelSurch.Insert;
  Bcd:= StrToBcd('2.01');
  showMessage('Bcd = ' + BcdToStr(Bcd));  // This works and shows 'Bcd = 2.01'
  POE_Data.FuelSurchFuelSur.AsBCD := Bcd;  // Line produces "Number is out of range." error
  POE_Data.FuelSurch.Post;
  POE_Data.FuelSurch.Close;
end;

The database connection is confirmed as good as I'm able to post to other tables. It just seems like this BCD field type is giving me issues.

Do I need to format the string differently before assigning it to the Bcd variable?

Answer 1

Internally the precision of a BCD is the total number of digits, not the number of digits after the decimal separator.

It's always an even number (when odd, 1 is added to it). The reason is that a byte stores 2 digits.

So if you try this:

procedure TForm1.Button1Click(Sender: TObject);
var
  Bcd: TBCD;
begin
  Bcd := StrToBcd('2.01', TFormatSettings.Invariant);
  ShowMessage(IntToStr(Bcd.Precision));
end;

you will see 4, because 3 digits are used, plus 1 to make it even.

Your field precision is only 2. If it represents the same as TBCD.Precision , it's not enough.

Note that BcdPrecision() returns the number of digits before the decimal separator, which is a bit confusing.