TdxDBBreadcrumbEdit does not work?

Hello Frank,

We've examined the project. The issue is caused by the fact that the ParentKey field should have unique values. You can read about this in the "TdxCustomDBBreadcrumbEdit.RootValue" help topic.
In your case, it contains several NULL values. To resolve this, you need to have unique values in the ParentKey field. For example, set the RootValue property to "-1" and set the same value to the "Parent" column of the top record in the TDBGrid.

Sorry, I give it up.
For a "nice to have" function, which could have been built in 5 minutes, to have to fumble for days.
And then there was also the problem with the INSERT. https://www.devexpress.com/Support/Center/Question/Details/T641833/insert-not-possible-tdxdbbreadcrumbedit

We also did not want to install another third-party component from another developer.
In the end, I'll do everything myself, once I have the data for the display in the Tree and additionally the manually synchronized and specially prepared data for the breadcrumb.

TreeListQuery: (TreeList.RootValue=NULL)

SQL
SELECT *  
FROM mytable  
ORDER BY id  

BreadcrumbQuery: (Breadcrumb.RootValue=NULL … müsste aber eigentlich -1 sein)

SQL
SELECT id, coalesce(parent, -1) AS parent, caption  
FROM mytable  
UNION  
SELECT -1, NULL, 'ROOT'  
ORDER BY id  

Delphi
procedure TFormDBUpdates.TreeListQuery_AfterOpen_AfterRefresh(Sender: TObject);  
begin  
  BreadcrumbQuery.OpenTable;  
  BreadcrumbQuery.Locate('id', TreeListQuery.AsInteger('id'));  
end;  

procedure TFormDBUpdates.TreeListQuery_AfterScroll(Sender: TObject);  
begin  
  //if not BreadcrumbQuery.IsEmpty  
  //    and (BreadcrumbQuery.AsInteger('id') <> TreeListQuery.AsInteger('id'))  
  //    and not TreeListQuery.ControlsDisabled then  
  //  BreadcrumbQuery.Locate('id', TreeListQuery.AsInteger('id'));  
  BreadcrumbTimer.Enabled := False;  
  BreadcrumbTimer.Enabled := True;  
end;  

procedure TFormDBUpdates.BreadcrumbTimer_OnTimer(Sender: TObject);  
begin  
  BreadcrumbTimer.Enabled := False;  
  if not BreadcrumbQuery.IsEmpty  
      and (BreadcrumbQuery.AsInteger('id') <> TreeListQuery.AsInteger('id'))  
      and not TreeListQuery.ControlsDisabled then  
    BreadcrumbQuery.Locate('id', TreeListQuery.AsInteger('id'));  
end;  

procedure TFormDBUpdates.BreadcrumbQuery_AfterScroll(Sender: TObject);  
begin  
  if (TreeListQuery.AsInteger('id') <> BreadcrumbQuery.AsInteger('id'))  
      and not BreadcrumbQuery.ControlsDisabled then  
    TreeListQuery.Locate('id', BreadcrumbQuery.AsInteger('id'));  
end;