Delphi: using BigInts from a database

Question

I´m using Delphi 7 with devart dbExpress to connect to SQLServer. The problem is that when I add a bigInt field to a ClientQuery it comes as TFMTBCDField.

And the TFMTBCDField don´t have a method to get the 64 bit value.

I can use the Field.AsVariant or the StrToInt64(Field.AsString) to pick this 64 bits value.

Is there a better way to pick/use this value?

Answer 1

I dont have Delphi 7 installed here anymore, but looking in the help, I see you can get as Float (Double), like this:

function GetFieldAsInt64(Field: TField): Int64;
begin
  Result:= Int64(Round(Field.GetAsFloat));
end;

And then, call the function:

var
  Value: Int64;
begin
  Value:= GetFieldAsInt64(MyFMTBCDField);

end;

Answer 2

You can convert the BCD to Variant and than to int64 with VarFMTBcdCreate from unit FMTBcd.

Try this:

var value64 : int64;
...
value64 := VarFMTBcdCreate(Field.Value);

Answer 3

Maybe add a TLargeIntField manualy to dataset, set it's FieldName to appropriate name and use such code:

SomeInt64Value := (qryMyQuery.FieldByName('blahblah') as TLargeIntField).AsLargeInt;

Do not remember exactly types, but it worked this way in Delphi6.

Answer 4

The data format for TFMTBCDField is the TBcd record from the FMTBcd unit. You can get that raw value by reading the field's Value or AsBCD properties.

Depending on what you need the value for, TBcd might be sufficient. That is, you might not need to convert it to an Int64. The FMTBcd unit provides functions to add, subtract, multiply, and divide TBcd values.

The unit provides no conversions to Int64. There are conversions to Variant, string, Currency, Double, and Integer. If we were going to write an Int64 conversion, the Integer conversion is probably a good place to start, so let's take a look at how it's implemented:

function BcdToInteger(const Bcd: TBcd; Truncate: Boolean = False): Integer;
var
  ABcd: TBcd;
begin
  if Truncate and (BcdScale(Bcd) > 0) then
    NormalizeBcd(Bcd, ABcd, Bcd.Precision, 0)
  else
    ABcd := Bcd;
  Result := StrToInt(BcdToStr(ABcd));    
end;

So, the VCL itself doesn't provide any more direct way to convert a TBcd to an Integer than to go through string. Therefore, it looks like your idea to call StrToInt64 on the string version of the field is fine.