Check out Nested Trees, Joe Celko has some articles about them. Mojomojo
has a pretty complete implementation of one in dbix:class if I remember.
Along the same lines, you could look at "modified pre-order tree
traversal". There's a nice sitepoint article about the method:
http://www.sitepoint.com/article/hierarchical-data-database
We use this for walking up and down large hierarchies and pulling out
sub-trees. Building the table is a bit of work initially and modifying
it (which we don't do) will probably need some careful planning, but
accessing the hierarchy like this is quick and easy.
John.
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