In this article, you will learn how to build an Ajax-based memory tree in Oracle Application Express (formerly HTML DB), based on any table that contains hierarchical data. I have added the word “memory” to the name here as, unlike with Carl’s example, this tree will “remember” which nodes are expanded, contracted, and selected across page views. There is also a search function that will locate any node in the tree and expand it accordingly—something that is not possible with the tree component supplied with Application Express. As the tree makes use of Ajax to fetch nodes as they are expanded, it can easily scale to support a table with thousands or more rows.