[AccessD] Treeview Problems

Well, I had 6 beers (and counting) ... But ... Shouldn't this already
exist?
> table (OrderDetailTypes) with one of each OrderDetailType... > so that
there's a combo when choosing the detail type upon entry?
If its not in a table, isn't it then a DISTINCT query, not a union, to
get a single list of all existing types? And, further, wouldn't your key
be: type  & customer, (I don't like multi-column pk either, but I see no
other choice) so if Select * where customer =1 and type = 4 returns no
records, there are no child rows to add.
I haven't seen your cool code for treeviews, but you may be up against a
situation where you have to customize something non-re-usable ... Going
now for # 7 

Steve




-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of MarkH
Sent: Wednesday, July 21, 2004 8:49 PM
To: 'Access Developers discussion and problem solving'
Subject: RE: [AccessD] Treeview Problems


Taking into account I'm on my third glass of wine and its real late...
Not sure if I took it all in but I have a similar situation where for
each node at a given level I want to create child nodes for all possible
parameters etc. I make the index (key of the node) unique by combining
the parameters (child) primary key with the parent nodes key. If I need
to create relationships where none exist (i.e. to get all records etc.)
I just create a dummy column in each query with the same value, e.g.
"'asd' AS theKey" and join on that...

Hth... 

Mark

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Arthur Fuller
Sent: 22 July 2004 00:48
To: AccessD
Subject: [AccessD] Treeview Problems


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

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