Nick,
I went searching for this recently too. Apart from the left/right id trick, you can also add the path as a field of the record. Thus:
ID PARENT_ID NAME PATH
1 null root root
2 1 A root.A
3 1 B root.B
4 2 X root.A.X
etc...
Now its easy to find all children of a given node:
Select * from NODES where path like 'root.A.%' // finds all children of root/A
To check if a record has a given ancestor:
path.startsWith(ancestor.path)
Of course, if you want to move the folders around, then you will have to update many records. Personally, I can't think of a clever piece of SQL to do that, but then again, I'm no expert.
If you are worried about using large names, you could use stringified ids as the path elements (e.g. node 4 would have a path: 1.2.4)
Lastly, I never bookmarked the link, but it should be easy to google.
Ciao,
Jonathan O'Connor
XCOM Dublin
Tapestry Stuff <[EMAIL PROTECTED]>
08/09/2005 20:27
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Hi, wondering if anyone has come up with a nicer way to present LARGE sets
of hierarchical data. Trees are fine but the large set makes the tree
unwieldy. We have been using tacos tree for a long time but now the set has
grown so large as to cause us grief with page layout and looong db queries.
I think that persisting the tree is out of the question as the set is too
large.
Any ideas?
--
Nick
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