Paradox BCD field - Number is out of Range error

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.