What is the best practice for fetching a tree of nodes from database for further rendering?

Question

Let\'s say we have a table with user comments. First-level comments have a reference to an article they are attached to. Deeper-level comments do not have this reference by desi

Answer 1

I usually recommend a design called Closure Table.

See example in my answer to What is the most efficient/elegant way to parse a flat table into a tree?

I also designed this presentation: Models for Hierarchical Data with SQL and PHP. I developed a PHP app that render a tree in 0.3 seconds, from a collection of hierarchical data with 490k nodes.

I blogged about Closure Table here: Rendering Trees with Closure Table.

I wrote a chapter about different strategies for hierarchical data in my book, SQL Antipatterns: Avoiding the Pitfalls of Database Programming.