[Lazarus] Filtering on date with TDbf

[shoKwave]

Am 30.01.2012 12:25, schrieb Koenraad Lelong:
> Hi,
>
> Lazarus 0.9.30
>
> I want to filter a TDbf. The field is a date.
> When I try in Filter in Lazarus :
> DATUM >= '1/1/2011'
>  or
> DATUM >= "1/1/2011"
>  or
> DATUM >= '1.1.2011'
>
> In my application :
> tblTik.Filter:='DATUM>='''+DateToStr(XferStart)+'''';
>
> I get an error :
> Index based on unknown field ">=".
>
> What am I doing wrong ?
>
> Regards,
>
> Koenraad Lelong.
>
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Hi,

IIRC, first of all you need an index based on the field(s) you want to 
filter. The error is shown because the index "DATUM" doesn't exists. 
Here is the real problem, I don't know how to create an index of ftDate. 
If I try an error is shown because only string and float fields are 
allowed. But you could convert your database and store all dates as 
strings. To format the date right you can use

procedure TForm1.FormCreate(Sender: TObject);
begin
   DefaultFormatSettings.DateSeparator:='.';
   DefaultFormatSettings.ShortDateFormat:='yyyy.mm.dd';
...
end;

With this lines DateToStr() should convert it right.

The filter property wants the name of the filter to compare with, not 
the name of the field.

  dbf1.Filter:='INDEXNAME>='+QuotedStr(DateToStr(XferStart));
  dbf1.Filtered:=true;

If the date-field is of ftString, the dates are correctly formatted and 
the index is build it should work.

Hope this helps.

regards

Ingo