Solved

Getting the FieldList from an SQL-Statement and add then to the Fields of a TADOQuery

Posted on 2007-03-22
5
475 Views
Last Modified: 2010-04-05
Hi all,

I have a TADOQuery-Component that can hold any SQL-Statement (Select-Query).
So, from my IDE, the FieldsEditor contains no fields.
When I fill the SQL-property with e.g. 'SELECT * FROM MyTable' and I open the Query, the results are showed in a DBGrid with the FieldNames displayed as ColumnHeaders.
So far so good...  BUT !!

Now I also want to include my own calculated field ('RowNumber') that holds the RecNo-Value of the current record.
So I have to add this field at runtime, just before I open mu Query.
This is my code to Add the Calulated Field to the DataSet:
procedure TfrmBaseQueryAnalyzerStandAlone.AddRowNumberField( DataSet: TDataSet; ColNr: Integer );
var
  fld: TIntegerField;
begin
  { First check if the Calculated Field already exists. If so, do nothing. If not, create it now. }
  if DataSet.FindField( 'CalcRowNumber' ) = nil then
  begin
    showmessage( inttostr( DataSet.FieldCount ) );
    DataSet.Close;
    fld :=  TIntegerField.Create( DataSet );
    with fld do
    fld.Name          := 'RowNumber';
    fld.FieldName     := 'RowNumber';
    fld.FieldKind     := fkCalculated;
    fld.Index         := ColNr-1;
    fld.DisplayLabel  := 'RijNr';
    fld.DataSet       := DataSet;
    DataSet.FieldDefs.Add( fld.Name, ftInteger, 0, False );
    showmessage( inttostr( DataSet.FieldCount ) );
    DataSet.Open;
  end;
end;

The code works fine, but the result is that my Dataset ONLY contains this calculated field.
So, I guess I should add all the fields which are in my SELECT-Clause of my query also to my DataSet by code.
Is there anyone who knows how to do this ?
Or maybe another way to accomplish what I want ?

Thanks in advance,

Wim.
0
Comment
Question by:wimmeyvaert
  • 3
  • 2
5 Comments
 
LVL 26

Accepted Solution

by:
EddieShipman earned 125 total points
ID: 18771409
try doing it this way:

var
  Field: TField;
  fld: TIntegerField;
  i: Integer;
begin
  if DataSet.FindField( 'CalcRowNumber' ) = nil then
  begin
    DataSet.Close;
    Dataset.FieldDefs.Update;
    for I := 0 to Dataset.FieldDefs.Count - 1 do
    begin
      Field := Dataset.FieldDefs[I].CreateField(Dataset);
    end;
    fld :=  TIntegerField.Create( Dataset );
    fld.Name          := 'RowNumber';
    fld.FieldName     := 'RowNumber';
    fld.Calculated    := True;
    fld.DataSet       := DataSet;
    fld.Index         := ColNr-1;
    fld.DisplayLabel  := 'RijNr';
    DataSet.Open;
  end;
end;
0
 
LVL 6

Author Comment

by:wimmeyvaert
ID: 18777938
Hi EddieShipman,

I will try out your suggestion and let you know the results.

Best regards,

Wim.
0
 
LVL 6

Author Comment

by:wimmeyvaert
ID: 18778620
Hi again,

I tested out your suggestion and it seems to work ....

BUT  !!!!

When I scroll in the DBGrid, I see that the first and the last item of the grid is havinf value '-1' as a RowNumber. When I export the dataset to a csv-file(with a self-written procedure) I also see in the csv-file the -1-value.

Any idea what's causing this behavior ?
I should get this solved too before I can put this application live.

Thanks in advance.

Wim.
0
 
LVL 26

Expert Comment

by:EddieShipman
ID: 18779516
Nope, I don't have the code that produces the "recno" for that column, do you?
0
 
LVL 6

Author Comment

by:wimmeyvaert
ID: 18806143
Hi EddieShipman,

I found a workaround for the -1 values in the first and last record of my dataset.
I put following code in my OnCalcFields-Event of my DataSet :

  if DataSet.FindField( 'RowNumber' ) <> nil then
  begin
    DataSet.FieldByName('RowNumber').AsInteger := DataSet.RecNo;
    if DataSet.FieldByName('RowNumber').AsInteger = -1 then
    begin
      if DataSet.Bof then
        DataSet.FieldByName('RowNumber').AsInteger := 1
      else if DataSet.Eof then
        DataSet.FieldByName('RowNumber').AsInteger := DataSet.Recordcount
    end;
  end;


This seems to work perfectly now.
I will grant you the points anyway for helping me out with the tricky part.
But I just wanted to post my code too, to offer a complete working solution.
Thanks again for your help.

Best regards,

Wim.
0

Featured Post

PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Delphi 2 61
Find and Replace Stream with 0s 8 63
Delphi Yen format 3 35
how to make 2 step back? ..\..\ ExtractFilePath (paramstr(0)) 5 17
Objective: - This article will help user in how to convert their numeric value become words. How to use 1. You can copy this code in your Unit as function 2. than you can perform your function by type this code The Code   (CODE) The Im…
Introduction Raise your hands if you were as upset with FireMonkey as I was when I discovered that there was no TListview.  I use TListView in almost all of my applications I've written, and I was not going to compromise by resorting to TStringGrid…
Nobody understands Phishing better than an anti-spam company. That’s why we are providing Phishing Awareness Training to our customers. According to a report by Verizon, only 3% of targeted users report malicious emails to management. With compan…

831 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question