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copied!<p>There is another way to store/retrieve a tree hierarchy as explained in <a href="http://www.fogcreek.com/blog/post/Subcases-and-Hierarchy.aspx" rel="nofollow noreferrer">this fogbugz</a> blog post:</p> <blockquote> <p>Turns out there's a pretty cool solution for this problem explained by Joe Celko. Instead of attempting to maintain a bunch of parent/child relationships all over your database -- which would necessitate recursive SQL queries to find all the descendents of a node -- we mark each case with a "left" and "right" value calculated by traversing the tree depth-first and counting as we go. A node's "left" value is set whenever it is first seen during traversal, and the "right" value is set when walking back up the tree away from the node. A picture probably makes more sense: </p> <p><img src="https://i.stack.imgur.com/4Otew.png" alt="enter image description here"></p> <p>The Nested Set SQL model lets us add case hierarchies without sacrificing performance.</p> <p>How does this help? Now we just ask for all the cases with a "left" value between 2 and 9 to find all of the descendents of B in one fast, indexed query. Ancestors of G are found by asking for nodes with "left" less than 6 (G's own "left") and "right" greater than 6. Works in all databases. Greatly increases performance -- particularly when querying large hierarchies</p> </blockquote> <p><a href="http://articles.sitepoint.com/article/hierarchical-data-database/2" rel="nofollow noreferrer">Here's another post</a> going into more detail. It's written using <code>Sql</code> and <code>php</code> but I think you can get the gist of it and easily translate in Linq to Sql.</p>

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