I'm looking for some advice re: how to search an entire dataset of invoices
and perform some calculations. I know I can use a TIB_Query to fetch the
invoice table sorted by invoice date, and then walk through it (using
qrInvoice.Next) building my subtotals for each day's sales as I go, and
keeping track of when the date changes, something like this:

with qrInvoice do begin
Open;
First;
while not eof do begin
if LastDate <> qrInvoice['INV_DATE'] then begin
DisplaySubTotal(LastDate, SubTotal);
SubTotal := qrInvoice['AMOUNT'];
LastDate := qrInvoice['INV_DATE'];
end else
SubTotal := SubTotal + qrInvoice['AMOUNT'];
Next;
end;
end;

My question is this: Is there a smarter (read "faster") way to do this? I
fear that this might take a long time to execute. I'm still figuring out
IBObjects and have also considered Filters or SQLWhereItems to get this done
but don't know what's appropriate. What's the best approach?

Thanks.

Bob.