[AccessD] Treeview Problems

Hi Arthur

Your problem is that the tree structure you aim for is not a true
branching tree structure as you at level 3 wish to list all possible
order detail types instead of those actually used.

However, it could be easily solved; you don't even need a union query,
you just need to - as you state - list all possible types, regardless
if they are used or not (that means just list them).
I guess it will break the system in your fancy tree code but you can
justify that for yourself by remembering that the code was created for
the clean tree structure. 

/gustav


> Some of you may have read my stuff about data-driven treeviews. Lately I
> have run into a problem using my own code, and am looking for a graceful
> way out.

> If you've read or at least run the code, then you know that it reduces
> the population of any given level to a simple select statement, using a
> query, a table, a view or a UDF. 

> However, my current problem is this:

> Let's suppose that you have parent table P and child table C, which
> references an FK F (i.e. OrderDetailType.... Assuming that there can be
> several types of OrderDetail, say CarRental, CampGroundSite,
> CanoeRental, etc. ((hey, it's summer and I need to revisit Killarney
> Park, one of the most beautiful places in the world, so forgive my
> examples)).

> Assume that Treeview level 1 is Customer. TV level 2 is Orders. Treeview
> Level 3 is all the possible order detail types. TV 4 is the detail types
> arranged under TV3.

> I.e.

> 1:
> ABC Company
> DEF Company

> 2:
> Order 123 from ABC
> Order 125 from ABC
> Order 126 from DEF
> Order 139 from DEF

> 3:
> CarRental
> CampGroundSite
> CanoeRental
> Etc.

> 4:
> Specific instances of CarRental, CampGroundSite, CanoeRental, etc.

> My code so far can handle levels 1 and 2 easily, one statement per
> level.

> The problem is at level 3. I want to populate the treeview at level 3
> with all the order detail types (CarRental, CampGroundSite, CanoeRental,
> etc.) for each Order. It's a simple UNION query to do this, but where do
> I get the unique key?

> Generalizing my problem, I have a simple (and dare I say it pretty cool)
> way of populating the data-driven levels of a treeview. But that's
> insufficient for my current problem. I need to populate the
> OrderDetailTypes level with all possible order detail types and then
> sub-populate level 4 with the corresponding children. I'm at a loss how
> to achieve this.

> One way to do it, which would fall conveniently into my current scheme,
> is to populate a bridge table (OrderDetailTypes) with one of each
> OrderDetailType... But that sucks, IMO. It stores a bunch of data that
> is most of the time unnecessary. I HATE unnecessary detail! I'll go
> there if I have to, but it makes me gag.

> Generalizing the problem....

> Given: code that can populate any tree-level with a simple select
> How to insert a level that is not data-driven or alternatively is
> data-driven but not with related FKs
> Treeview nodes insist upon unique keys (understandably so). But how
> should I manufacture said unique keys given that no physical rows
> correspond to them.
> Maybe the generalization is: how to relate a grandchild to a parent in
> the absence of parental data? That might be an incorrect phrasing, but
> that's what I mean.

> I hope that I have stated the problem clearly enough for you to follow
> the logic. If not, please reply for further clarification.

> Any suggestions much appreciated.

> TIA,
> Arthur