Simple Delphi DBcharting - delphi

Question

So, the problem I'm having is that I'm displaying two bars on the graph for each student, I just want one of them. They're the correct height though, so that's good.
This is my Delphi source code;
strlstField := TStringList.Create();
ADOQGetResults.SQL.clear;
ADOQGetResults.SQL.Add(
'SELECT Results.StudentID, SUM(Results.Rawmark) as TRM, StudentInfo.Fname '+
'FROM (StudentInfo INNER JOIN Results ON StudentInfo.StudentID = Results.StudentID) '+
'WHERE (((StudentInfo.StudentID)=Results.StudentID)) AND Results.TestID =12 '+
'GROUP BY StudentInfo.Fname, Results.StudentID'
);
ADOQGetResults.Active := True;
ADOQGetResults.Open;
DBChart1.Title.Text.Clear;
DBChart1.Title.Text.Add('Class leaderboard');
DBChart1.Title.Font.Size := 15;
DBChart1.LeftAxis.Title.Font.Size := 12;
DBChart1.LeftAxis.Title.Caption := 'Total marks';
DBChart1.BottomAxis.Title.Font.Size := 12;
DBChart1.BottomAxis.Title.Caption := 'Student';
//Charting Series
//To Remove Old Series
for intCnt := DBChart1.SeriesCount -1 downto 0 do
DBChart1.Series[intCnt].Free;
//To Add New Series
for intCnt := 1 to ADOQGetResults.FieldCount - 1 do
begin
strlstField.Add(ADOQGetResults.FieldList[intCnt].FieldName);
DBChart1.AddSeries(TBarSeries.Create(nil));
end;
//To set source for Series
for intCnt:= 0 to DBChart1.SeriesCount -1 do
begin
with DBChart1 do begin
Series[intCnt].Clear;
Series[intCnt].Title := strlstField[intCnt];
Series[intCnt].ParentChart := DBChart1;
Series[intCnt].DataSource := ADOQGetResults;
Series[intCnt].XLabelsSource := 'Fname';
Series[intCnt].YValues.ValueSource := 'TRM';
end;
end;
I've been trying to work-out whats going wrong all day, so if anyone can help at all I'd be very grateful!
Here is what the graph looks like right now;
http://oi48.tinypic.com/6qelba.jpg

Answer 1

Why are you looping over EVERY FIELD in the result (you return 3 fields in your query) and adding one series PER field in the result? It's almost like you think that the field count equals your row count or something. Secondly I would venture to guess that something in your query plus your data (that we can't see) could result in you getting more rows in your query result than you were expecting.
Why are you destroying and re-adding series when your query always returns 3 fields, 1 field is not charted, 1 field is the series label source and 1 field is the series value source? Just statically create one series at designtime in your dfm and forget all this crazy runtime stuff. Have you tried double clicking dbchart and adding ONE BarChart series there?
This works and is much less code. You don't need to open a dataset twice, by the way. Note that I'm using the DBDEMOS.mdb database that comes with Delphi here so that everyone can play along. Add a db chart and at DESIGNTIME add ONE barchart series to it. Configure as desired. Use this code. dataset below is a TADODataset.
-
dataset.CommandText := 'select EmpNo,FirstName,Salary from employee';
dataset.Active := True;
DBChart1.Title.Text.Clear;
DBChart1.Title.Text.Add('Class leaderboard');
DBChart1.Title.Font.Size := 15;
DBChart1.LeftAxis.Title.Font.Size := 12;
DBChart1.LeftAxis.Title.Caption := 'Total marks';
DBChart1.BottomAxis.Title.Font.Size := 12;
DBChart1.BottomAxis.Title.Caption := 'Student';
if DBChart1.SeriesCount<1 then
begin
raise Exception.Create('Add series to your chart in the dfm ONCE.');
end;
//To set source for Series
with DBChart1 do begin
Series[0].Title := 'Test';
Series[0].DataSource := dataset;
Series[0].XLabelsSource := 'FirstName';
Series[0].YValues.ValueSource := 'Salary';
end;
Note that this is still more code than you absolutely have to write. You could do most of this if not all in dfm (form designer).