Normal Behavior?

[lespaul]

I have a DBGrid that displays working hours for jurors (total hours is a calculated field in the query):

Date       Type      Time In      Time Out     Total Hours
1/18/2005  ORIENT    8:30 AM      4:00 PM        7.5
1/19/2005  JUROR    11:00 AM      5:30 PM        6.5
1/20/2005  JUROR    11:00 AM      2:30 PM        3.5
1/21/2005  DLYPNL    9:30 AM      1:00 PM        3.5
1/25/2005  DLYPNL    2:00 PM      4:00 PM        2.0
1/26/2005  JUROR     1:00 PM      3:00 PM        2.0
1/27/2005  DLYPNL    2:00 PM      4:00 PM        2.0

on the same form is a TOTAL HOURS display. I calculate this total in the calculated field code:

procedure TfrmJurorInformation.qryJurorHoursCalcFields(DataSet: TDataSet);
begin
  with qryJurorHours do
  begin
    if FieldByName('TIMEOUT').AsInteger <> 0 then
      FieldByName('TotalTime').Value := FloatToStr((HourSpan(IntToTime(FieldByName('TimeIn').AsInteger), IntToTime(FIeldByName('TimeOut').AsInteger))))
    else
      FieldByName('TotalTime').Value := '??';
    [b]if FieldByName('TotalTime').value <> '??' then
      dblHrsWorked := dblHrsWorked + FieldByName('TotalTime').value;[/b]
  end;
end;

So for the data above, the total hours worked is 27.

The DBGrid is large enough to hold 6 entries. Subsequently the Hours Worked label only sums those first 6 entries. So, for the example above, only the first six entries are summed and the total hours displayed is 25. If I enlarge the DBGrid to fit 10 rows, the total hours display is correct at 27.

I moved the bolded calculation to the OnShow event and it works correctly now, I was just wondering if this is normal.

Thanks for any insight!!!

Les

 

[donvittorio]

Many types of dataset will only fetch records as it needs to, rather than immediately fetching all appropriate records, so if your dbgrid is only big enough to display 6 records then only the first 6 records will initially be fetched. If you scroll down the grid then the subsequent records will be fetched as necessary.
The OnCalcFields event is triggered each time a record is fetched from the db, and hence your dblHrsWorked field will only contain a total for those records that have been fetched so far.
If you have put the calculation in your OnShow event, then I guess you are iterating through all records of the dataset and hence forcing the dataset to fetch all records, and hence your calculation will be correct.
In summary: yes, I think this is normal!

Steve

 

[hilfy]

Also, as an FYI, I've had problems in the past with calculated fields on queries not refreshing correctly when I edit data. If the data you're querying is for display only, then this should not be a problem. However, if you're allowing editing of the data, I would be wary of the calculated field not displaying the correct value.

-Dell

A computer only does what you actually told it to do - not what you thought you told it to do.

 

[lespaul]

Thanks for the insight!!

Dell - this is only for display, no editing allowed!!!

Les