Fast Relational method of storing tree data (for instance threaded comments on articles)

Question

I have a cms which stores comments against articles. These comments can be both threaded and non threaded. Although technically they are the same just with the reply column

Answer 1

I just did this myself, actually! I used the nested set model of representing hierarchical data in a relational database.

Managing Hierarchical Data in MySQL was pure gold for me. Nested sets are the second model described in that article.