How to retrieve data from database and display in Ttreeview in delphi

Question

Please help me to populate a tree view from SQL database dynamically. I am very new to delphi

Answer 1

Switch to TADOQuery and then try something like this:

procedure TForm1.Button1Click(Sender: TObject);
var
  CurrentDeptID, RecordDeptID: Integer;
  RootNode, DeptNode: TTreeNode;
begin
  CurrentDeptID := 0;
  TreeList1.Items.Clear;
  RootNode := TreeList1.Items.Add(nil, 'Departments');
  DeptNode := nil;
  ADOQuery1.SQL.Text := 'SELECT sd.DeptID, sd.Name, d.Dept FROM SubDepartments sd INNER JOIN Departments d ON (sd.DeptID = d.DeptID) ORDER BY d.Dept, sd.Name';
  ADOQuery1.Open;
  try
    ADOQuery1.First;
    while not ADOQuery1.Eof do
    begin
      RecordDeptID := ADOQuery1.FieldByName('DeptID').AsInteger;
      if (DeptNode = nil) or (RecordDeptID <> CurrentDeptID) then
      begin
        DeptNode := TreeList1.Items.AddChild(RootNode, ADOQuery1.FieldByName('Dept').AsString);
        CurrentDeptID := RecordDeptID;
      end;
      TreeList1.Items.AddChild(DeptNode, ADOQuery1.FieldByName('Name').AsString);
      ADOQuery1.Next;
    end;
  finally
    ADOQuery1.Close;
  end;
end;