nested-sets

having an e-commerce application under development i am trying to get my head around the following problem: I have my categories realized through the awesome_nested_set plugin. If I list my articles through selecting one category everything works fine, but for some links I want to show all the products of one category and the products of its child categories. here is the controller code that works fine with only one category: # products_controller.rb def index if params[:category] @category = Category.find(params[:category]) #@products = @category.product_list @products = @category.products

I'm using nested sets (aka modified preorder tree traversal) to store a list of groups, and I'm trying to find a quick way to generate breadcrumbs (as a string, not a table) for ALL of the groups at once. My data is also stored using the adjacency list model (there are triggers to keep the two in sync). So for example: ID Name ParentId Left Right 0 Node A 0 1 12 1 Node B 0 2 5 2 Node C 1 3 4 3 Node D 0 6 11 4 Node E 3 7 8 5 Node F 4 9 9 Which represents the tree: Node A Node B Node C Node D Node E Node F I would like to be able to have a user-defined function that returns a table: ID

I am looking to use this concept in one of my upcoming project. More info: Managing Hierarchical Data in MySQL . Please share your experiences good or bad with examples. I am adding more information to make it more broad: I have child items that can have more than one parent (example: a user can belong to city and also a group called UserDefinedRegion), which the typical hierarchical models do not support, whether it is adjacency list or nested sets. I am pasting the use case here for clarity: Background: Currently the system has a fixed hierarchy in place which is State->County->City->User

Is there a simple way to display the entire nested set when using this plugin? What I would like to do is display an unordered list of root nodes with another unordered list inside each child that also contains children and so on? Any advice appreciated. Thanks. There are a few ways to do this. The simplest is to just start with the roots and parse each node and it's children. The first thing I'd do is make a partial for a the node markup: _your_model.html.erb <li> <%= your_model.name %> <% unless your_model.children.empty? %> <ul> <%= render your_model.children %> </ul> <% end %> </li> Next

Given that I have this resultset structure (superfluous fields have been stripped) Id | ParentId | Name | Depth ---------------------------- is it possible to have the records returned in tree order i.e. Parent then Children , if a Child is a Parent , then their Children , if not then Sibling , etc? For example, Id | ParentId | Name | Depth ---------------------------- 1 NULL Major 1 2 1 Minor 2 3 1 Minor 2 4 3 Build 3 5 3 Build 3 6 1 Minor 2 /* etc, etc */ The only way that I can think of doing this would be to follow this article - Improve hierarchy performance using nested sets and include