Forum OpenACS Q&A: Re: Categories -- Perhaps I am missing something basic

In general hierarchical tables that is implemented with postgres on OpenACS has a tree_sortkey column.  And you can use tree_* plsql.

Here is are samples:

http://cvs.openacs.org/cvs/*checkout*/openacs-4/contrib/packages/bcms/tcl/bcms-category-procs-postgresql.xql?rev=1.1

You may also want to look at Timo's categories as the cr_keywords is the older implementation and I know will be changed.